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authorKartik K. Agaram <vc@akkartik.com>2017-05-13 12:50:07 -0700
committerKartik K. Agaram <vc@akkartik.com>2017-05-13 17:21:10 -0700
commitef6116cbaf9368e490bfdec1c6404396ac161026 (patch)
tree686bf4b486778a9705381ebdfeced3dbbbdf1519 /html/edit
parent0c0d1ea5cdb96a98e7eb62edbd1acb534ae12940 (diff)
downloadmu-ef6116cbaf9368e490bfdec1c6404396ac161026.tar.gz
3855
Diffstat (limited to 'html/edit')
-rw-r--r--html/edit/001-editor.mu.html912
-rw-r--r--html/edit/002-typing.mu.html90
-rw-r--r--html/edit/003-shortcuts.mu.html176
-rw-r--r--html/edit/004-programming-environment.mu.html942
-rw-r--r--html/edit/005-sandbox.mu.html726
-rw-r--r--html/edit/006-sandbox-copy.mu.html302
-rw-r--r--html/edit/007-sandbox-delete.mu.html534
-rw-r--r--html/edit/008-sandbox-edit.mu.html416
-rw-r--r--html/edit/009-sandbox-test.mu.html152
-rw-r--r--html/edit/010-sandbox-trace.mu.html102
-rw-r--r--html/edit/011-errors.mu.html10
-rw-r--r--html/edit/012-editor-undo.mu.html58
12 files changed, 2231 insertions, 2189 deletions
diff --git a/html/edit/001-editor.mu.html b/html/edit/001-editor.mu.html
index 14307ec2..b17df3bd 100644
--- a/html/edit/001-editor.mu.html
+++ b/html/edit/001-editor.mu.html
@@ -69,472 +69,474 @@ if ('onhashchange' in window) {
 <span id="L6" class="LineNr">  6 </span>  <span class="Constant">local-scope</span>
 <span id="L7" class="LineNr">  7 </span>  <span class="Constant">load-ingredients</span>
 <span id="L8" class="LineNr">  8 </span>  open-console
-<span id="L9" class="LineNr">  9 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> text, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-<span id="L10" class="LineNr"> 10 </span>  <a href='001-editor.mu.html#L121'>render</a> <span class="Constant">0/screen</span>, e
-<span id="L11" class="LineNr"> 11 </span>  <a href='../084console.mu.html#L88'>wait-for-event</a> <span class="Constant">0/console</span>
-<span id="L12" class="LineNr"> 12 </span>  close-console
-<span id="L13" class="LineNr"> 13 </span>]
-<span id="L14" class="LineNr"> 14 </span>
-<span id="L15" class="LineNr"> 15 </span><span class="muScenario">scenario</span> editor-renders-text-to-screen [
-<span id="L16" class="LineNr"> 16 </span>  <span class="Constant">local-scope</span>
-<span id="L17" class="LineNr"> 17 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L18" class="LineNr"> 18 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-<span id="L19" class="LineNr"> 19 </span>  run [
-<span id="L20" class="LineNr"> 20 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L21" class="LineNr"> 21 </span>  ]
-<span id="L22" class="LineNr"> 22 </span>  screen-should-contain [
-<span id="L23" class="LineNr"> 23 </span>  <span class="Conceal">¦</span> <span class="Comment"># top line of screen reserved for menu</span>
-<span id="L24" class="LineNr"> 24 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
-<span id="L25" class="LineNr"> 25 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc       .</span>
+<span id="L9" class="LineNr">  9 </span>  <a href='../081print.mu.html#L623'>hide-screen</a> <span class="Constant">0/screen</span>
+<span id="L10" class="LineNr"> 10 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> text, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L11" class="LineNr"> 11 </span>  <a href='001-editor.mu.html#L123'>render</a> <span class="Constant">0/screen</span>, e
+<span id="L12" class="LineNr"> 12 </span>  <a href='../081print.mu.html#L631'>show-screen</a> <span class="Constant">0/screen</span>
+<span id="L13" class="LineNr"> 13 </span>  <a href='../084console.mu.html#L88'>wait-for-event</a> <span class="Constant">0/console</span>
+<span id="L14" class="LineNr"> 14 </span>  close-console
+<span id="L15" class="LineNr"> 15 </span>]
+<span id="L16" class="LineNr"> 16 </span>
+<span id="L17" class="LineNr"> 17 </span><span class="muScenario">scenario</span> editor-renders-text-to-screen [
+<span id="L18" class="LineNr"> 18 </span>  <span class="Constant">local-scope</span>
+<span id="L19" class="LineNr"> 19 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
+<span id="L20" class="LineNr"> 20 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L21" class="LineNr"> 21 </span>  run [
+<span id="L22" class="LineNr"> 22 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L23" class="LineNr"> 23 </span>  ]
+<span id="L24" class="LineNr"> 24 </span>  screen-should-contain [
+<span id="L25" class="LineNr"> 25 </span>  <span class="Conceal">¦</span> <span class="Comment"># top line of screen reserved for menu</span>
 <span id="L26" class="LineNr"> 26 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
-<span id="L27" class="LineNr"> 27 </span>  ]
-<span id="L28" class="LineNr"> 28 </span>]
-<span id="L29" class="LineNr"> 29 </span>
-<span id="L30" class="LineNr"> 30 </span><span class="muData">container</span> editor [
-<span id="L31" class="LineNr"> 31 </span>  <span class="Comment"># editable text: doubly linked list of characters (head contains a special sentinel)</span>
-<span id="L32" class="LineNr"> 32 </span>  data:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
-<span id="L33" class="LineNr"> 33 </span>  top-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
-<span id="L34" class="LineNr"> 34 </span>  bottom-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
-<span id="L35" class="LineNr"> 35 </span>  <span class="Comment"># location before cursor inside data</span>
-<span id="L36" class="LineNr"> 36 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
-<span id="L37" class="LineNr"> 37 </span>
-<span id="L38" class="LineNr"> 38 </span>  <span class="Comment"># raw bounds of display area on screen</span>
-<span id="L39" class="LineNr"> 39 </span>  <span class="Comment"># always displays from row 1 (leaving row 0 for a menu) and at most until bottom of screen</span>
-<span id="L40" class="LineNr"> 40 </span>  left:num
-<span id="L41" class="LineNr"> 41 </span>  right:num
-<span id="L42" class="LineNr"> 42 </span>  bottom:num
-<span id="L43" class="LineNr"> 43 </span>  <span class="Comment"># raw screen coordinates of cursor</span>
-<span id="L44" class="LineNr"> 44 </span>  cursor-row:num
-<span id="L45" class="LineNr"> 45 </span>  cursor-column:num
-<span id="L46" class="LineNr"> 46 </span>]
-<span id="L47" class="LineNr"> 47 </span>
-<span id="L48" class="LineNr"> 48 </span><span class="Comment"># creates a new editor widget</span>
-<span id="L49" class="LineNr"> 49 </span><span class="Comment">#   right is exclusive</span>
-<span id="L50" class="LineNr"> 50 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L50'>new-editor</a> s:text, left:num, right:num<span class="muRecipe"> -&gt; </span>result:&amp;:editor [
-<span id="L51" class="LineNr"> 51 </span>  <span class="Constant">local-scope</span>
-<span id="L52" class="LineNr"> 52 </span>  <span class="Constant">load-ingredients</span>
-<span id="L53" class="LineNr"> 53 </span>  <span class="Comment"># no clipping of bounds</span>
-<span id="L54" class="LineNr"> 54 </span>  right <span class="Special">&lt;-</span> subtract right,<span class="Constant"> 1</span>
-<span id="L55" class="LineNr"> 55 </span>  result <span class="Special">&lt;-</span> new <span class="Constant">editor:type</span>
-<span id="L56" class="LineNr"> 56 </span>  <span class="Comment"># initialize screen-related fields</span>
-<span id="L57" class="LineNr"> 57 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">left:offset</span>, left
-<span id="L58" class="LineNr"> 58 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">right:offset</span>, right
-<span id="L59" class="LineNr"> 59 </span>  <span class="Comment"># initialize cursor coordinates</span>
-<span id="L60" class="LineNr"> 60 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">cursor-row:offset</span>, <span class="Constant">1/top</span>
-<span id="L61" class="LineNr"> 61 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">cursor-column:offset</span>, left
-<span id="L62" class="LineNr"> 62 </span>  <span class="Comment"># initialize empty contents</span>
-<span id="L63" class="LineNr"> 63 </span>  init:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> push <span class="Constant">167/§</span>, <span class="Constant">0/tail</span>
-<span id="L64" class="LineNr"> 64 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">data:offset</span>, init
-<span id="L65" class="LineNr"> 65 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">top-of-screen:offset</span>, init
-<span id="L66" class="LineNr"> 66 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">before-cursor:offset</span>, init
-<span id="L67" class="LineNr"> 67 </span>  result <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L71'>insert-text</a> result, s
-<span id="L68" class="LineNr"> 68 </span><span class="Constant">  <a href='001-editor.mu.html#L68'>&lt;editor-initialization&gt;</a></span>
-<span id="L69" class="LineNr"> 69 </span>]
-<span id="L70" class="LineNr"> 70 </span>
-<span id="L71" class="LineNr"> 71 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L71'>insert-text</a> editor:&amp;:editor, text:text<span class="muRecipe"> -&gt; </span>editor:&amp;:editor [
-<span id="L72" class="LineNr"> 72 </span>  <span class="Constant">local-scope</span>
-<span id="L73" class="LineNr"> 73 </span>  <span class="Constant">load-ingredients</span>
-<span id="L74" class="LineNr"> 74 </span>  <span class="Comment"># early exit if text is empty</span>
-<span id="L75" class="LineNr"> 75 </span>  <span class="muControl">return-unless</span> text
-<span id="L76" class="LineNr"> 76 </span>  len:num <span class="Special">&lt;-</span> length *text
-<span id="L77" class="LineNr"> 77 </span>  <span class="muControl">return-unless</span> len
-<span id="L78" class="LineNr"> 78 </span>  idx:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
-<span id="L79" class="LineNr"> 79 </span>  <span class="Comment"># now we can start appending the rest, character by character</span>
-<span id="L80" class="LineNr"> 80 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
-<span id="L81" class="LineNr"> 81 </span>  <span class="Delimiter">{</span>
-<span id="L82" class="LineNr"> 82 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal idx, len
-<span id="L83" class="LineNr"> 83 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L84" class="LineNr"> 84 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> index *text, idx
-<span id="L85" class="LineNr"> 85 </span>  <span class="Conceal">¦</span> insert c, curr
-<span id="L86" class="LineNr"> 86 </span>  <span class="Conceal">¦</span> <span class="Comment"># next iter</span>
-<span id="L87" class="LineNr"> 87 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L88" class="LineNr"> 88 </span>  <span class="Conceal">¦</span> idx <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
-<span id="L89" class="LineNr"> 89 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L90" class="LineNr"> 90 </span>  <span class="Delimiter">}</span>
-<span id="L91" class="LineNr"> 91 </span>]
-<span id="L92" class="LineNr"> 92 </span>
-<span id="L93" class="LineNr"> 93 </span><span class="muScenario">scenario</span> editor-initializes-without-data [
-<span id="L94" class="LineNr"> 94 </span>  <span class="Constant">local-scope</span>
-<span id="L95" class="LineNr"> 95 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">3/height</span>
-<span id="L96" class="LineNr"> 96 </span>  run [
-<span id="L97" class="LineNr"> 97 </span>  <span class="Conceal">¦</span> e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">0/data</span>, <span class="Constant">2/left</span>, <span class="Constant">5/right</span>
-<span id="L98" class="LineNr"> 98 </span>  <span class="Conceal">¦</span> 2:editor/<span class="Special">raw</span> <span class="Special">&lt;-</span> copy *e
-<span id="L99" class="LineNr"> 99 </span>  ]
-<span id="L100" class="LineNr">100 </span>  memory-should-contain [
-<span id="L101" class="LineNr">101 </span>  <span class="Conceal">¦</span> <span class="Comment"># 2 (data) &lt;- just the § sentinel</span>
-<span id="L102" class="LineNr">102 </span>  <span class="Conceal">¦</span> <span class="Comment"># 3 (top of screen) &lt;- the § sentinel</span>
-<span id="L103" class="LineNr">103 </span>  <span class="Conceal">¦</span><span class="Constant"> 4</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># bottom-of-screen; null since text fits on screen</span>
-<span id="L104" class="LineNr">104 </span>  <span class="Conceal">¦</span> <span class="Comment"># 5 (before cursor) &lt;- the § sentinel</span>
-<span id="L105" class="LineNr">105 </span>  <span class="Conceal">¦</span><span class="Constant"> 6</span> <span class="Special">&lt;-</span><span class="Constant"> 2</span>  <span class="Comment"># left</span>
-<span id="L106" class="LineNr">106 </span>  <span class="Conceal">¦</span><span class="Constant"> 7</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># right  (inclusive)</span>
-<span id="L107" class="LineNr">107 </span>  <span class="Conceal">¦</span><span class="Constant"> 8</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># bottom (not set until render)</span>
-<span id="L108" class="LineNr">108 </span>  <span class="Conceal">¦</span><span class="Constant"> 9</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># cursor row</span>
-<span id="L109" class="LineNr">109 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 2</span>  <span class="Comment"># cursor column</span>
-<span id="L110" class="LineNr">110 </span>  ]
-<span id="L111" class="LineNr">111 </span>  screen-should-contain [
-<span id="L112" class="LineNr">112 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L113" class="LineNr">113 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L27" class="LineNr"> 27 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc       .</span>
+<span id="L28" class="LineNr"> 28 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
+<span id="L29" class="LineNr"> 29 </span>  ]
+<span id="L30" class="LineNr"> 30 </span>]
+<span id="L31" class="LineNr"> 31 </span>
+<span id="L32" class="LineNr"> 32 </span><span class="muData">container</span> editor [
+<span id="L33" class="LineNr"> 33 </span>  <span class="Comment"># editable text: doubly linked list of characters (head contains a special sentinel)</span>
+<span id="L34" class="LineNr"> 34 </span>  data:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
+<span id="L35" class="LineNr"> 35 </span>  top-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
+<span id="L36" class="LineNr"> 36 </span>  bottom-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
+<span id="L37" class="LineNr"> 37 </span>  <span class="Comment"># location before cursor inside data</span>
+<span id="L38" class="LineNr"> 38 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char
+<span id="L39" class="LineNr"> 39 </span>
+<span id="L40" class="LineNr"> 40 </span>  <span class="Comment"># raw bounds of display area on screen</span>
+<span id="L41" class="LineNr"> 41 </span>  <span class="Comment"># always displays from row 1 (leaving row 0 for a menu) and at most until bottom of screen</span>
+<span id="L42" class="LineNr"> 42 </span>  left:num
+<span id="L43" class="LineNr"> 43 </span>  right:num
+<span id="L44" class="LineNr"> 44 </span>  bottom:num
+<span id="L45" class="LineNr"> 45 </span>  <span class="Comment"># raw screen coordinates of cursor</span>
+<span id="L46" class="LineNr"> 46 </span>  cursor-row:num
+<span id="L47" class="LineNr"> 47 </span>  cursor-column:num
+<span id="L48" class="LineNr"> 48 </span>]
+<span id="L49" class="LineNr"> 49 </span>
+<span id="L50" class="LineNr"> 50 </span><span class="Comment"># creates a new editor widget</span>
+<span id="L51" class="LineNr"> 51 </span><span class="Comment">#   right is exclusive</span>
+<span id="L52" class="LineNr"> 52 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L52'>new-editor</a> s:text, left:num, right:num<span class="muRecipe"> -&gt; </span>result:&amp;:editor [
+<span id="L53" class="LineNr"> 53 </span>  <span class="Constant">local-scope</span>
+<span id="L54" class="LineNr"> 54 </span>  <span class="Constant">load-ingredients</span>
+<span id="L55" class="LineNr"> 55 </span>  <span class="Comment"># no clipping of bounds</span>
+<span id="L56" class="LineNr"> 56 </span>  right <span class="Special">&lt;-</span> subtract right,<span class="Constant"> 1</span>
+<span id="L57" class="LineNr"> 57 </span>  result <span class="Special">&lt;-</span> new <span class="Constant">editor:type</span>
+<span id="L58" class="LineNr"> 58 </span>  <span class="Comment"># initialize screen-related fields</span>
+<span id="L59" class="LineNr"> 59 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">left:offset</span>, left
+<span id="L60" class="LineNr"> 60 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">right:offset</span>, right
+<span id="L61" class="LineNr"> 61 </span>  <span class="Comment"># initialize cursor coordinates</span>
+<span id="L62" class="LineNr"> 62 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">cursor-row:offset</span>, <span class="Constant">1/top</span>
+<span id="L63" class="LineNr"> 63 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">cursor-column:offset</span>, left
+<span id="L64" class="LineNr"> 64 </span>  <span class="Comment"># initialize empty contents</span>
+<span id="L65" class="LineNr"> 65 </span>  init:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> push <span class="Constant">167/§</span>, <span class="Constant">0/tail</span>
+<span id="L66" class="LineNr"> 66 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">data:offset</span>, init
+<span id="L67" class="LineNr"> 67 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">top-of-screen:offset</span>, init
+<span id="L68" class="LineNr"> 68 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">before-cursor:offset</span>, init
+<span id="L69" class="LineNr"> 69 </span>  result <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L73'>insert-text</a> result, s
+<span id="L70" class="LineNr"> 70 </span><span class="Constant">  <a href='001-editor.mu.html#L70'>&lt;editor-initialization&gt;</a></span>
+<span id="L71" class="LineNr"> 71 </span>]
+<span id="L72" class="LineNr"> 72 </span>
+<span id="L73" class="LineNr"> 73 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L73'>insert-text</a> editor:&amp;:editor, text:text<span class="muRecipe"> -&gt; </span>editor:&amp;:editor [
+<span id="L74" class="LineNr"> 74 </span>  <span class="Constant">local-scope</span>
+<span id="L75" class="LineNr"> 75 </span>  <span class="Constant">load-ingredients</span>
+<span id="L76" class="LineNr"> 76 </span>  <span class="Comment"># early exit if text is empty</span>
+<span id="L77" class="LineNr"> 77 </span>  <span class="muControl">return-unless</span> text
+<span id="L78" class="LineNr"> 78 </span>  len:num <span class="Special">&lt;-</span> length *text
+<span id="L79" class="LineNr"> 79 </span>  <span class="muControl">return-unless</span> len
+<span id="L80" class="LineNr"> 80 </span>  idx:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L81" class="LineNr"> 81 </span>  <span class="Comment"># now we can start appending the rest, character by character</span>
+<span id="L82" class="LineNr"> 82 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
+<span id="L83" class="LineNr"> 83 </span>  <span class="Delimiter">{</span>
+<span id="L84" class="LineNr"> 84 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal idx, len
+<span id="L85" class="LineNr"> 85 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
+<span id="L86" class="LineNr"> 86 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> index *text, idx
+<span id="L87" class="LineNr"> 87 </span>  <span class="Conceal">¦</span> insert c, curr
+<span id="L88" class="LineNr"> 88 </span>  <span class="Conceal">¦</span> <span class="Comment"># next iter</span>
+<span id="L89" class="LineNr"> 89 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L90" class="LineNr"> 90 </span>  <span class="Conceal">¦</span> idx <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
+<span id="L91" class="LineNr"> 91 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L92" class="LineNr"> 92 </span>  <span class="Delimiter">}</span>
+<span id="L93" class="LineNr"> 93 </span>]
+<span id="L94" class="LineNr"> 94 </span>
+<span id="L95" class="LineNr"> 95 </span><span class="muScenario">scenario</span> editor-initializes-without-data [
+<span id="L96" class="LineNr"> 96 </span>  <span class="Constant">local-scope</span>
+<span id="L97" class="LineNr"> 97 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">3/height</span>
+<span id="L98" class="LineNr"> 98 </span>  run [
+<span id="L99" class="LineNr"> 99 </span>  <span class="Conceal">¦</span> e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">0/data</span>, <span class="Constant">2/left</span>, <span class="Constant">5/right</span>
+<span id="L100" class="LineNr">100 </span>  <span class="Conceal">¦</span> 2:editor/<span class="Special">raw</span> <span class="Special">&lt;-</span> copy *e
+<span id="L101" class="LineNr">101 </span>  ]
+<span id="L102" class="LineNr">102 </span>  memory-should-contain [
+<span id="L103" class="LineNr">103 </span>  <span class="Conceal">¦</span> <span class="Comment"># 2 (data) &lt;- just the § sentinel</span>
+<span id="L104" class="LineNr">104 </span>  <span class="Conceal">¦</span> <span class="Comment"># 3 (top of screen) &lt;- the § sentinel</span>
+<span id="L105" class="LineNr">105 </span>  <span class="Conceal">¦</span><span class="Constant"> 4</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># bottom-of-screen; null since text fits on screen</span>
+<span id="L106" class="LineNr">106 </span>  <span class="Conceal">¦</span> <span class="Comment"># 5 (before cursor) &lt;- the § sentinel</span>
+<span id="L107" class="LineNr">107 </span>  <span class="Conceal">¦</span><span class="Constant"> 6</span> <span class="Special">&lt;-</span><span class="Constant"> 2</span>  <span class="Comment"># left</span>
+<span id="L108" class="LineNr">108 </span>  <span class="Conceal">¦</span><span class="Constant"> 7</span> <span class="Special">&lt;-</span><span class="Constant"> 4</span>  <span class="Comment"># right  (inclusive)</span>
+<span id="L109" class="LineNr">109 </span>  <span class="Conceal">¦</span><span class="Constant"> 8</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># bottom (not set until render)</span>
+<span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</span><span class="Constant"> 9</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># cursor row</span>
+<span id="L111" class="LineNr">111 </span>  <span class="Conceal">¦</span><span class="Constant"> 10</span> <span class="Special">&lt;-</span><span class="Constant"> 2</span>  <span class="Comment"># cursor column</span>
+<span id="L112" class="LineNr">112 </span>  ]
+<span id="L113" class="LineNr">113 </span>  screen-should-contain [
 <span id="L114" class="LineNr">114 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L115" class="LineNr">115 </span>  ]
-<span id="L116" class="LineNr">116 </span>]
-<span id="L117" class="LineNr">117 </span>
-<span id="L118" class="LineNr">118 </span><span class="Comment"># Assumes cursor should be at coordinates (cursor-row, cursor-column) and</span>
-<span id="L119" class="LineNr">119 </span><span class="Comment"># updates before-cursor to match. Might also move coordinates if they're</span>
-<span id="L120" class="LineNr">120 </span><span class="Comment"># outside text.</span>
-<span id="L121" class="LineNr">121 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor<span class="muRecipe"> -&gt; </span>last-row:num, last-column:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor [
-<span id="L122" class="LineNr">122 </span>  <span class="Constant">local-scope</span>
-<span id="L123" class="LineNr">123 </span>  <span class="Constant">load-ingredients</span>
-<span id="L124" class="LineNr">124 </span>  <span class="muControl">return-unless</span> editor, <span class="Constant">1/top</span>, <span class="Constant">0/left</span>
-<span id="L125" class="LineNr">125 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
-<span id="L126" class="LineNr">126 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L127" class="LineNr">127 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
-<span id="L128" class="LineNr">128 </span>  <span class="Comment"># traversing editor</span>
-<span id="L129" class="LineNr">129 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
-<span id="L130" class="LineNr">130 </span>  <a href='../065duplex_list.mu.html#L36'>prev</a>:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
-<span id="L131" class="LineNr">131 </span>  curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L132" class="LineNr">132 </span>  <span class="Comment"># traversing screen</span>
-<span id="L133" class="LineNr">133 </span>  color:num <span class="Special">&lt;-</span> copy <span class="Constant">7/white</span>
-<span id="L134" class="LineNr">134 </span>  row:num <span class="Special">&lt;-</span> copy <span class="Constant">1/top</span>
-<span id="L135" class="LineNr">135 </span>  column:num <span class="Special">&lt;-</span> copy left
-<span id="L136" class="LineNr">136 </span>  cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
-<span id="L137" class="LineNr">137 </span>  cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
-<span id="L138" class="LineNr">138 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
-<span id="L139" class="LineNr">139 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L140" class="LineNr">140 </span>  <span class="Delimiter">{</span>
-<span id="L141" class="LineNr">141 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
-<span id="L142" class="LineNr">142 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
-<span id="L143" class="LineNr">143 </span>  <span class="Conceal">¦</span> off-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
-<span id="L144" class="LineNr">144 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> off-screen?
-<span id="L145" class="LineNr">145 </span>  <span class="Conceal">¦</span> <span class="Comment"># update editor.before-cursor</span>
-<span id="L146" class="LineNr">146 </span>  <span class="Conceal">¦</span> <span class="Comment"># Doing so at the start of each iteration ensures it stays one step behind</span>
-<span id="L147" class="LineNr">147 </span>  <span class="Conceal">¦</span> <span class="Comment"># the current character.</span>
-<span id="L148" class="LineNr">148 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L149" class="LineNr">149 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor-row?:bool <span class="Special">&lt;-</span> equal row, cursor-row
-<span id="L150" class="LineNr">150 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor-row?
-<span id="L151" class="LineNr">151 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor?:bool <span class="Special">&lt;-</span> equal column, cursor-column
-<span id="L152" class="LineNr">152 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor?
-<span id="L153" class="LineNr">153 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> before-cursor <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L36'>prev</a>
-<span id="L154" class="LineNr">154 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L155" class="LineNr">155 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
-<span id="L156" class="LineNr">156 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;character-c-received&gt;</span>
-<span id="L157" class="LineNr">157 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L158" class="LineNr">158 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># newline? move to left rather than 0</span>
-<span id="L159" class="LineNr">159 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
-<span id="L160" class="LineNr">160 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> newline?
-<span id="L161" class="LineNr">161 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># adjust cursor if necessary</span>
-<span id="L162" class="LineNr">162 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L163" class="LineNr">163 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor-row?:bool <span class="Special">&lt;-</span> equal row, cursor-row
-<span id="L164" class="LineNr">164 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor-row?
-<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> left-of-cursor?:bool <span class="Special">&lt;-</span> lesser-than column, cursor-column
-<span id="L166" class="LineNr">166 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> left-of-cursor?
-<span id="L167" class="LineNr">167 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> cursor-column <span class="Special">&lt;-</span> copy column
-<span id="L168" class="LineNr">168 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> before-cursor <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L36'>prev</a> curr
-<span id="L169" class="LineNr">169 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L170" class="LineNr">170 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of line in this window</span>
-<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
-<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># skip to next line</span>
-<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L175" class="LineNr">175 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
-<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
-<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># at right? wrap. even if there's only one more letter left; we need</span>
-<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># room for clicking on the cursor after it.</span>
-<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> equal column, right
-<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-right?
-<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print wrap icon</span>
-<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> wrap-icon:char <span class="Special">&lt;-</span> copy <span class="Constant">8617/loop-back-to-left</span>
-<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
-<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># don't increment curr</span>
-<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
-<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
-<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
-<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
-<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L199" class="LineNr">199 </span>  <span class="Delimiter">}</span>
-<span id="L200" class="LineNr">200 </span>  <span class="Comment"># save first character off-screen</span>
-<span id="L201" class="LineNr">201 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom-of-screen:offset</span>, curr
-<span id="L202" class="LineNr">202 </span>  <span class="Comment"># is cursor to the right of the last line? move to end</span>
-<span id="L203" class="LineNr">203 </span>  <span class="Delimiter">{</span>
-<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span> at-cursor-row?:bool <span class="Special">&lt;-</span> equal row, cursor-row
-<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span> cursor-outside-line?:bool <span class="Special">&lt;-</span> lesser-or-equal column, cursor-column
-<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span> before-cursor-on-same-line?:bool <span class="Special">&lt;-</span> and at-cursor-row?, cursor-outside-line?
-<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> above-cursor-row?:bool <span class="Special">&lt;-</span> lesser-than row, cursor-row
-<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span> before-cursor?:bool <span class="Special">&lt;-</span> or before-cursor-on-same-line?, above-cursor-row?
-<span id="L209" class="LineNr">209 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> before-cursor?
-<span id="L210" class="LineNr">210 </span>  <span class="Conceal">¦</span> cursor-row <span class="Special">&lt;-</span> copy row
-<span id="L211" class="LineNr">211 </span>  <span class="Conceal">¦</span> cursor-column <span class="Special">&lt;-</span> copy column
-<span id="L212" class="LineNr">212 </span>  <span class="Conceal">¦</span> before-cursor <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L36'>prev</a>
-<span id="L213" class="LineNr">213 </span>  <span class="Delimiter">}</span>
-<span id="L214" class="LineNr">214 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom:offset</span>, row
-<span id="L215" class="LineNr">215 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
-<span id="L216" class="LineNr">216 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
-<span id="L217" class="LineNr">217 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, before-cursor
-<span id="L218" class="LineNr">218 </span>  <span class="muControl">return</span> row, column
-<span id="L219" class="LineNr">219 </span>]
-<span id="L220" class="LineNr">220 </span>
-<span id="L221" class="LineNr">221 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L221'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, row:num, column:num, left:num, right:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L222" class="LineNr">222 </span>  <span class="Constant">local-scope</span>
-<span id="L223" class="LineNr">223 </span>  <span class="Constant">load-ingredients</span>
-<span id="L224" class="LineNr">224 </span>  <span class="Comment"># if it's the real screen, use the optimized primitive</span>
-<span id="L225" class="LineNr">225 </span>  <span class="Delimiter">{</span>
-<span id="L226" class="LineNr">226 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L227" class="LineNr">227 </span>  <span class="Conceal">¦</span> clear-display-from row, column, left, right
-<span id="L228" class="LineNr">228 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
-<span id="L229" class="LineNr">229 </span>  <span class="Delimiter">}</span>
-<span id="L230" class="LineNr">230 </span>  <span class="Comment"># if not, go the slower route</span>
-<span id="L231" class="LineNr">231 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L232" class="LineNr">232 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
-<span id="L233" class="LineNr">233 </span>  <a href='001-editor.mu.html#L236'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
-<span id="L234" class="LineNr">234 </span>]
-<span id="L235" class="LineNr">235 </span>
-<span id="L236" class="LineNr">236 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L236'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, row:num, left:num, right:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
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-<span id="L238" class="LineNr">238 </span>  <span class="Constant">load-ingredients</span>
-<span id="L239" class="LineNr">239 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L240" class="LineNr">240 </span>  <span class="Comment"># if it's the real screen, use the optimized primitive</span>
-<span id="L241" class="LineNr">241 </span>  <span class="Delimiter">{</span>
-<span id="L242" class="LineNr">242 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L243" class="LineNr">243 </span>  <span class="Conceal">¦</span> clear-display-from row, left, left, right
-<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
-<span id="L245" class="LineNr">245 </span>  <span class="Delimiter">}</span>
-<span id="L246" class="LineNr">246 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
-<span id="L247" class="LineNr">247 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L248" class="LineNr">248 </span>  <span class="Delimiter">{</span>
-<span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span> at-bottom-of-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
-<span id="L250" class="LineNr">250 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> at-bottom-of-screen?
-<span id="L251" class="LineNr">251 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
-<span id="L252" class="LineNr">252 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
-<span id="L253" class="LineNr">253 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L254" class="LineNr">254 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L255" class="LineNr">255 </span>  <span class="Delimiter">}</span>
-<span id="L256" class="LineNr">256 </span>]
-<span id="L257" class="LineNr">257 </span>
-<span id="L258" class="LineNr">258 </span><span class="muScenario">scenario</span> editor-prints-multiple-lines [
-<span id="L259" class="LineNr">259 </span>  <span class="Constant">local-scope</span>
-<span id="L260" class="LineNr">260 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L261" class="LineNr">261 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
-<span id="L262" class="LineNr">262 </span><span class="Constant">def]</span>
-<span id="L263" class="LineNr">263 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-<span id="L264" class="LineNr">264 </span>  run [
-<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L266" class="LineNr">266 </span>  ]
-<span id="L267" class="LineNr">267 </span>  screen-should-contain [
-<span id="L268" class="LineNr">268 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L269" class="LineNr">269 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc  .</span>
-<span id="L270" class="LineNr">270 </span>  <span class="Conceal">¦</span><span class="Constant"> .def  .</span>
-<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L272" class="LineNr">272 </span>  ]
-<span id="L273" class="LineNr">273 </span>]
-<span id="L274" class="LineNr">274 </span>
-<span id="L275" class="LineNr">275 </span><span class="muScenario">scenario</span> editor-handles-offsets [
-<span id="L276" class="LineNr">276 </span>  <span class="Constant">local-scope</span>
-<span id="L277" class="LineNr">277 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L278" class="LineNr">278 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
-<span id="L279" class="LineNr">279 </span>  run [
-<span id="L280" class="LineNr">280 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L281" class="LineNr">281 </span>  ]
-<span id="L282" class="LineNr">282 </span>  screen-should-contain [
-<span id="L283" class="LineNr">283 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L284" class="LineNr">284 </span>  <span class="Conceal">¦</span><span class="Constant"> . abc .</span>
+<span id="L115" class="LineNr">115 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L116" class="LineNr">116 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L117" class="LineNr">117 </span>  ]
+<span id="L118" class="LineNr">118 </span>]
+<span id="L119" class="LineNr">119 </span>
+<span id="L120" class="LineNr">120 </span><span class="Comment"># Assumes cursor should be at coordinates (cursor-row, cursor-column) and</span>
+<span id="L121" class="LineNr">121 </span><span class="Comment"># updates before-cursor to match. Might also move coordinates if they're</span>
+<span id="L122" class="LineNr">122 </span><span class="Comment"># outside text.</span>
+<span id="L123" class="LineNr">123 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor<span class="muRecipe"> -&gt; </span>last-row:num, last-column:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor [
+<span id="L124" class="LineNr">124 </span>  <span class="Constant">local-scope</span>
+<span id="L125" class="LineNr">125 </span>  <span class="Constant">load-ingredients</span>
+<span id="L126" class="LineNr">126 </span>  <span class="muControl">return-unless</span> editor, <span class="Constant">1/top</span>, <span class="Constant">0/left</span>
+<span id="L127" class="LineNr">127 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
+<span id="L128" class="LineNr">128 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L129" class="LineNr">129 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
+<span id="L130" class="LineNr">130 </span>  <span class="Comment"># traversing editor</span>
+<span id="L131" class="LineNr">131 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
+<span id="L132" class="LineNr">132 </span>  <a href='../065duplex_list.mu.html#L36'>prev</a>:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
+<span id="L133" class="LineNr">133 </span>  curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L134" class="LineNr">134 </span>  <span class="Comment"># traversing screen</span>
+<span id="L135" class="LineNr">135 </span>  color:num <span class="Special">&lt;-</span> copy <span class="Constant">7/white</span>
+<span id="L136" class="LineNr">136 </span>  row:num <span class="Special">&lt;-</span> copy <span class="Constant">1/top</span>
+<span id="L137" class="LineNr">137 </span>  column:num <span class="Special">&lt;-</span> copy left
+<span id="L138" class="LineNr">138 </span>  cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
+<span id="L139" class="LineNr">139 </span>  cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
+<span id="L140" class="LineNr">140 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
+<span id="L141" class="LineNr">141 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L142" class="LineNr">142 </span>  <span class="Delimiter">{</span>
+<span id="L143" class="LineNr">143 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
+<span id="L144" class="LineNr">144 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
+<span id="L145" class="LineNr">145 </span>  <span class="Conceal">¦</span> off-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L146" class="LineNr">146 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> off-screen?
+<span id="L147" class="LineNr">147 </span>  <span class="Conceal">¦</span> <span class="Comment"># update editor.before-cursor</span>
+<span id="L148" class="LineNr">148 </span>  <span class="Conceal">¦</span> <span class="Comment"># Doing so at the start of each iteration ensures it stays one step behind</span>
+<span id="L149" class="LineNr">149 </span>  <span class="Conceal">¦</span> <span class="Comment"># the current character.</span>
+<span id="L150" class="LineNr">150 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L151" class="LineNr">151 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor-row?:bool <span class="Special">&lt;-</span> equal row, cursor-row
+<span id="L152" class="LineNr">152 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor-row?
+<span id="L153" class="LineNr">153 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor?:bool <span class="Special">&lt;-</span> equal column, cursor-column
+<span id="L154" class="LineNr">154 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor?
+<span id="L155" class="LineNr">155 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> before-cursor <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L36'>prev</a>
+<span id="L156" class="LineNr">156 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L157" class="LineNr">157 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
+<span id="L158" class="LineNr">158 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;character-c-received&gt;</span>
+<span id="L159" class="LineNr">159 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L160" class="LineNr">160 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># newline? move to left rather than 0</span>
+<span id="L161" class="LineNr">161 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
+<span id="L162" class="LineNr">162 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> newline?
+<span id="L163" class="LineNr">163 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># adjust cursor if necessary</span>
+<span id="L164" class="LineNr">164 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor-row?:bool <span class="Special">&lt;-</span> equal row, cursor-row
+<span id="L166" class="LineNr">166 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor-row?
+<span id="L167" class="LineNr">167 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> left-of-cursor?:bool <span class="Special">&lt;-</span> lesser-than column, cursor-column
+<span id="L168" class="LineNr">168 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> left-of-cursor?
+<span id="L169" class="LineNr">169 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> cursor-column <span class="Special">&lt;-</span> copy column
+<span id="L170" class="LineNr">170 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> before-cursor <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L36'>prev</a> curr
+<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of line in this window</span>
+<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># skip to next line</span>
+<span id="L175" class="LineNr">175 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
+<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
+<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
+<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># at right? wrap. even if there's only one more letter left; we need</span>
+<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># room for clicking on the cursor after it.</span>
+<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> equal column, right
+<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-right?
+<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print wrap icon</span>
+<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> wrap-icon:char <span class="Special">&lt;-</span> copy <span class="Constant">8617/loop-back-to-left</span>
+<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
+<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
+<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># don't increment curr</span>
+<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
+<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
+<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
+<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
+<span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L201" class="LineNr">201 </span>  <span class="Delimiter">}</span>
+<span id="L202" class="LineNr">202 </span>  <span class="Comment"># save first character off-screen</span>
+<span id="L203" class="LineNr">203 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom-of-screen:offset</span>, curr
+<span id="L204" class="LineNr">204 </span>  <span class="Comment"># is cursor to the right of the last line? move to end</span>
+<span id="L205" class="LineNr">205 </span>  <span class="Delimiter">{</span>
+<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span> at-cursor-row?:bool <span class="Special">&lt;-</span> equal row, cursor-row
+<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> cursor-outside-line?:bool <span class="Special">&lt;-</span> lesser-or-equal column, cursor-column
+<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span> before-cursor-on-same-line?:bool <span class="Special">&lt;-</span> and at-cursor-row?, cursor-outside-line?
+<span id="L209" class="LineNr">209 </span>  <span class="Conceal">¦</span> above-cursor-row?:bool <span class="Special">&lt;-</span> lesser-than row, cursor-row
+<span id="L210" class="LineNr">210 </span>  <span class="Conceal">¦</span> before-cursor?:bool <span class="Special">&lt;-</span> or before-cursor-on-same-line?, above-cursor-row?
+<span id="L211" class="LineNr">211 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> before-cursor?
+<span id="L212" class="LineNr">212 </span>  <span class="Conceal">¦</span> cursor-row <span class="Special">&lt;-</span> copy row
+<span id="L213" class="LineNr">213 </span>  <span class="Conceal">¦</span> cursor-column <span class="Special">&lt;-</span> copy column
+<span id="L214" class="LineNr">214 </span>  <span class="Conceal">¦</span> before-cursor <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L36'>prev</a>
+<span id="L215" class="LineNr">215 </span>  <span class="Delimiter">}</span>
+<span id="L216" class="LineNr">216 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom:offset</span>, row
+<span id="L217" class="LineNr">217 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
+<span id="L218" class="LineNr">218 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
+<span id="L219" class="LineNr">219 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, before-cursor
+<span id="L220" class="LineNr">220 </span>  <span class="muControl">return</span> row, column
+<span id="L221" class="LineNr">221 </span>]
+<span id="L222" class="LineNr">222 </span>
+<span id="L223" class="LineNr">223 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L223'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, row:num, column:num, left:num, right:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L224" class="LineNr">224 </span>  <span class="Constant">local-scope</span>
+<span id="L225" class="LineNr">225 </span>  <span class="Constant">load-ingredients</span>
+<span id="L226" class="LineNr">226 </span>  <span class="Comment"># if it's the real screen, use the optimized primitive</span>
+<span id="L227" class="LineNr">227 </span>  <span class="Delimiter">{</span>
+<span id="L228" class="LineNr">228 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L229" class="LineNr">229 </span>  <span class="Conceal">¦</span> clear-display-from row, column, left, right
+<span id="L230" class="LineNr">230 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
+<span id="L231" class="LineNr">231 </span>  <span class="Delimiter">}</span>
+<span id="L232" class="LineNr">232 </span>  <span class="Comment"># if not, go the slower route</span>
+<span id="L233" class="LineNr">233 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L234" class="LineNr">234 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L235" class="LineNr">235 </span>  <a href='001-editor.mu.html#L238'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
+<span id="L236" class="LineNr">236 </span>]
+<span id="L237" class="LineNr">237 </span>
+<span id="L238" class="LineNr">238 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L238'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, row:num, left:num, right:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L239" class="LineNr">239 </span>  <span class="Constant">local-scope</span>
+<span id="L240" class="LineNr">240 </span>  <span class="Constant">load-ingredients</span>
+<span id="L241" class="LineNr">241 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L242" class="LineNr">242 </span>  <span class="Comment"># if it's the real screen, use the optimized primitive</span>
+<span id="L243" class="LineNr">243 </span>  <span class="Delimiter">{</span>
+<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span> clear-display-from row, left, left, right
+<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
+<span id="L247" class="LineNr">247 </span>  <span class="Delimiter">}</span>
+<span id="L248" class="LineNr">248 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L249" class="LineNr">249 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L250" class="LineNr">250 </span>  <span class="Delimiter">{</span>
+<span id="L251" class="LineNr">251 </span>  <span class="Conceal">¦</span> at-bottom-of-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L252" class="LineNr">252 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> at-bottom-of-screen?
+<span id="L253" class="LineNr">253 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L254" class="LineNr">254 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L255" class="LineNr">255 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L257" class="LineNr">257 </span>  <span class="Delimiter">}</span>
+<span id="L258" class="LineNr">258 </span>]
+<span id="L259" class="LineNr">259 </span>
+<span id="L260" class="LineNr">260 </span><span class="muScenario">scenario</span> editor-prints-multiple-lines [
+<span id="L261" class="LineNr">261 </span>  <span class="Constant">local-scope</span>
+<span id="L262" class="LineNr">262 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
+<span id="L263" class="LineNr">263 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
+<span id="L264" class="LineNr">264 </span><span class="Constant">def]</span>
+<span id="L265" class="LineNr">265 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L266" class="LineNr">266 </span>  run [
+<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L268" class="LineNr">268 </span>  ]
+<span id="L269" class="LineNr">269 </span>  screen-should-contain [
+<span id="L270" class="LineNr">270 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc  .</span>
+<span id="L272" class="LineNr">272 </span>  <span class="Conceal">¦</span><span class="Constant"> .def  .</span>
+<span id="L273" class="LineNr">273 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L274" class="LineNr">274 </span>  ]
+<span id="L275" class="LineNr">275 </span>]
+<span id="L276" class="LineNr">276 </span>
+<span id="L277" class="LineNr">277 </span><span class="muScenario">scenario</span> editor-handles-offsets [
+<span id="L278" class="LineNr">278 </span>  <span class="Constant">local-scope</span>
+<span id="L279" class="LineNr">279 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
+<span id="L280" class="LineNr">280 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
+<span id="L281" class="LineNr">281 </span>  run [
+<span id="L282" class="LineNr">282 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L283" class="LineNr">283 </span>  ]
+<span id="L284" class="LineNr">284 </span>  screen-should-contain [
 <span id="L285" class="LineNr">285 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L286" class="LineNr">286 </span>  ]
-<span id="L287" class="LineNr">287 </span>]
-<span id="L288" class="LineNr">288 </span>
-<span id="L289" class="LineNr">289 </span><span class="muScenario">scenario</span> editor-prints-multiple-lines-at-offset [
-<span id="L290" class="LineNr">290 </span>  <span class="Constant">local-scope</span>
-<span id="L291" class="LineNr">291 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L292" class="LineNr">292 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
-<span id="L293" class="LineNr">293 </span><span class="Constant">def]</span>
-<span id="L294" class="LineNr">294 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
-<span id="L295" class="LineNr">295 </span>  run [
-<span id="L296" class="LineNr">296 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L297" class="LineNr">297 </span>  ]
-<span id="L298" class="LineNr">298 </span>  screen-should-contain [
-<span id="L299" class="LineNr">299 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L300" class="LineNr">300 </span>  <span class="Conceal">¦</span><span class="Constant"> . abc .</span>
-<span id="L301" class="LineNr">301 </span>  <span class="Conceal">¦</span><span class="Constant"> . def .</span>
-<span id="L302" class="LineNr">302 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L303" class="LineNr">303 </span>  ]
-<span id="L304" class="LineNr">304 </span>]
-<span id="L305" class="LineNr">305 </span>
-<span id="L306" class="LineNr">306 </span><span class="muScenario">scenario</span> editor-wraps-long-lines [
-<span id="L307" class="LineNr">307 </span>  <span class="Constant">local-scope</span>
-<span id="L308" class="LineNr">308 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L309" class="LineNr">309 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc def]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-<span id="L310" class="LineNr">310 </span>  run [
-<span id="L311" class="LineNr">311 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L312" class="LineNr">312 </span>  ]
-<span id="L313" class="LineNr">313 </span>  screen-should-contain [
-<span id="L314" class="LineNr">314 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L315" class="LineNr">315 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc ↩.</span>
-<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span><span class="Constant"> .def  .</span>
-<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L318" class="LineNr">318 </span>  ]
-<span id="L319" class="LineNr">319 </span>  screen-should-contain-in-color <span class="Constant">245/grey</span> [
-<span id="L320" class="LineNr">320 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L321" class="LineNr">321 </span>  <span class="Conceal">¦</span><span class="Constant"> .    ↩.</span>
+<span id="L286" class="LineNr">286 </span>  <span class="Conceal">¦</span><span class="Constant"> . abc .</span>
+<span id="L287" class="LineNr">287 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L288" class="LineNr">288 </span>  ]
+<span id="L289" class="LineNr">289 </span>]
+<span id="L290" class="LineNr">290 </span>
+<span id="L291" class="LineNr">291 </span><span class="muScenario">scenario</span> editor-prints-multiple-lines-at-offset [
+<span id="L292" class="LineNr">292 </span>  <span class="Constant">local-scope</span>
+<span id="L293" class="LineNr">293 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
+<span id="L294" class="LineNr">294 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
+<span id="L295" class="LineNr">295 </span><span class="Constant">def]</span>
+<span id="L296" class="LineNr">296 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">1/left</span>, <span class="Constant">5/right</span>
+<span id="L297" class="LineNr">297 </span>  run [
+<span id="L298" class="LineNr">298 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L299" class="LineNr">299 </span>  ]
+<span id="L300" class="LineNr">300 </span>  screen-should-contain [
+<span id="L301" class="LineNr">301 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L302" class="LineNr">302 </span>  <span class="Conceal">¦</span><span class="Constant"> . abc .</span>
+<span id="L303" class="LineNr">303 </span>  <span class="Conceal">¦</span><span class="Constant"> . def .</span>
+<span id="L304" class="LineNr">304 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L305" class="LineNr">305 </span>  ]
+<span id="L306" class="LineNr">306 </span>]
+<span id="L307" class="LineNr">307 </span>
+<span id="L308" class="LineNr">308 </span><span class="muScenario">scenario</span> editor-wraps-long-lines [
+<span id="L309" class="LineNr">309 </span>  <span class="Constant">local-scope</span>
+<span id="L310" class="LineNr">310 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
+<span id="L311" class="LineNr">311 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc def]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L312" class="LineNr">312 </span>  run [
+<span id="L313" class="LineNr">313 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L314" class="LineNr">314 </span>  ]
+<span id="L315" class="LineNr">315 </span>  screen-should-contain [
+<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc ↩.</span>
+<span id="L318" class="LineNr">318 </span>  <span class="Conceal">¦</span><span class="Constant"> .def  .</span>
+<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L320" class="LineNr">320 </span>  ]
+<span id="L321" class="LineNr">321 </span>  screen-should-contain-in-color <span class="Constant">245/grey</span> [
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-<span id="L323" class="LineNr">323 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L324" class="LineNr">324 </span>  ]
-<span id="L325" class="LineNr">325 </span>]
-<span id="L326" class="LineNr">326 </span>
-<span id="L327" class="LineNr">327 </span><span class="muScenario">scenario</span> editor-wraps-barely-long-lines [
-<span id="L328" class="LineNr">328 </span>  <span class="Constant">local-scope</span>
-<span id="L329" class="LineNr">329 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L330" class="LineNr">330 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-<span id="L331" class="LineNr">331 </span>  run [
-<span id="L332" class="LineNr">332 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L333" class="LineNr">333 </span>  ]
-<span id="L334" class="LineNr">334 </span>  <span class="Comment"># still wrap, even though the line would fit. We need room to click on the</span>
-<span id="L335" class="LineNr">335 </span>  <span class="Comment"># end of the line</span>
-<span id="L336" class="LineNr">336 </span>  screen-should-contain [
-<span id="L337" class="LineNr">337 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L338" class="LineNr">338 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .abcd↩.</span>
-<span id="L339" class="LineNr">339 </span>  <span class="Conceal">¦</span><span class="Constant"> .e    .</span>
-<span id="L340" class="LineNr">340 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L341" class="LineNr">341 </span>  ]
-<span id="L342" class="LineNr">342 </span>  screen-should-contain-in-color <span class="Constant">245/grey</span> [
-<span id="L343" class="LineNr">343 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L344" class="LineNr">344 </span>  <span class="Conceal">¦</span><span class="Constant"> .    ↩.</span>
+<span id="L323" class="LineNr">323 </span>  <span class="Conceal">¦</span><span class="Constant"> .    ↩.</span>
+<span id="L324" class="LineNr">324 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L325" class="LineNr">325 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L326" class="LineNr">326 </span>  ]
+<span id="L327" class="LineNr">327 </span>]
+<span id="L328" class="LineNr">328 </span>
+<span id="L329" class="LineNr">329 </span><span class="muScenario">scenario</span> editor-wraps-barely-long-lines [
+<span id="L330" class="LineNr">330 </span>  <span class="Constant">local-scope</span>
+<span id="L331" class="LineNr">331 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
+<span id="L332" class="LineNr">332 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L333" class="LineNr">333 </span>  run [
+<span id="L334" class="LineNr">334 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L335" class="LineNr">335 </span>  ]
+<span id="L336" class="LineNr">336 </span>  <span class="Comment"># still wrap, even though the line would fit. We need room to click on the</span>
+<span id="L337" class="LineNr">337 </span>  <span class="Comment"># end of the line</span>
+<span id="L338" class="LineNr">338 </span>  screen-should-contain [
+<span id="L339" class="LineNr">339 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L340" class="LineNr">340 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .abcd↩.</span>
+<span id="L341" class="LineNr">341 </span>  <span class="Conceal">¦</span><span class="Constant"> .e    .</span>
+<span id="L342" class="LineNr">342 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L343" class="LineNr">343 </span>  ]
+<span id="L344" class="LineNr">344 </span>  screen-should-contain-in-color <span class="Constant">245/grey</span> [
 <span id="L345" class="LineNr">345 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L346" class="LineNr">346 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L347" class="LineNr">347 </span>  ]
-<span id="L348" class="LineNr">348 </span>]
-<span id="L349" class="LineNr">349 </span>
-<span id="L350" class="LineNr">350 </span><span class="muScenario">scenario</span> editor-with-empty-text [
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-<span id="L352" class="LineNr">352 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L353" class="LineNr">353 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-<span id="L354" class="LineNr">354 </span>  run [
-<span id="L355" class="LineNr">355 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L356" class="LineNr">356 </span>  <span class="Conceal">¦</span> 3:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *e, <span class="Constant">cursor-row:offset</span>
-<span id="L357" class="LineNr">357 </span>  <span class="Conceal">¦</span> 4:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *e, <span class="Constant">cursor-column:offset</span>
-<span id="L358" class="LineNr">358 </span>  ]
-<span id="L359" class="LineNr">359 </span>  screen-should-contain [
-<span id="L360" class="LineNr">360 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L361" class="LineNr">361 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L346" class="LineNr">346 </span>  <span class="Conceal">¦</span><span class="Constant"> .    ↩.</span>
+<span id="L347" class="LineNr">347 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L348" class="LineNr">348 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L349" class="LineNr">349 </span>  ]
+<span id="L350" class="LineNr">350 </span>]
+<span id="L351" class="LineNr">351 </span>
+<span id="L352" class="LineNr">352 </span><span class="muScenario">scenario</span> editor-with-empty-text [
+<span id="L353" class="LineNr">353 </span>  <span class="Constant">local-scope</span>
+<span id="L354" class="LineNr">354 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
+<span id="L355" class="LineNr">355 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L356" class="LineNr">356 </span>  run [
+<span id="L357" class="LineNr">357 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L358" class="LineNr">358 </span>  <span class="Conceal">¦</span> 3:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *e, <span class="Constant">cursor-row:offset</span>
+<span id="L359" class="LineNr">359 </span>  <span class="Conceal">¦</span> 4:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *e, <span class="Constant">cursor-column:offset</span>
+<span id="L360" class="LineNr">360 </span>  ]
+<span id="L361" class="LineNr">361 </span>  screen-should-contain [
 <span id="L362" class="LineNr">362 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L363" class="LineNr">363 </span>  ]
-<span id="L364" class="LineNr">364 </span>  memory-should-contain [
-<span id="L365" class="LineNr">365 </span>  <span class="Conceal">¦</span><span class="Constant"> 3</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># cursor row</span>
-<span id="L366" class="LineNr">366 </span>  <span class="Conceal">¦</span><span class="Constant"> 4</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># cursor column</span>
-<span id="L367" class="LineNr">367 </span>  ]
-<span id="L368" class="LineNr">368 </span>]
-<span id="L369" class="LineNr">369 </span>
-<span id="L370" class="LineNr">370 </span><span class="Comment"># just a little color for Mu code</span>
+<span id="L363" class="LineNr">363 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L364" class="LineNr">364 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L365" class="LineNr">365 </span>  ]
+<span id="L366" class="LineNr">366 </span>  memory-should-contain [
+<span id="L367" class="LineNr">367 </span>  <span class="Conceal">¦</span><span class="Constant"> 3</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>  <span class="Comment"># cursor row</span>
+<span id="L368" class="LineNr">368 </span>  <span class="Conceal">¦</span><span class="Constant"> 4</span> <span class="Special">&lt;-</span><span class="Constant"> 0</span>  <span class="Comment"># cursor column</span>
+<span id="L369" class="LineNr">369 </span>  ]
+<span id="L370" class="LineNr">370 </span>]
 <span id="L371" class="LineNr">371 </span>
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-<span id="L374" class="LineNr">374 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L375" class="LineNr">375 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
-<span id="L376" class="LineNr">376 </span><span class="Constant"># de</span>
-<span id="L377" class="LineNr">377 </span><span class="Constant">f]</span>
-<span id="L378" class="LineNr">378 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
-<span id="L379" class="LineNr">379 </span>  run [
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-<span id="L381" class="LineNr">381 </span>  ]
-<span id="L382" class="LineNr">382 </span>  screen-should-contain [
-<span id="L383" class="LineNr">383 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L384" class="LineNr">384 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc  .</span>
-<span id="L385" class="LineNr">385 </span>  <span class="Conceal">¦</span><span class="Constant"> .# de .</span>
-<span id="L386" class="LineNr">386 </span>  <span class="Conceal">¦</span><span class="Constant"> .f    .</span>
-<span id="L387" class="LineNr">387 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L388" class="LineNr">388 </span>  ]
-<span id="L389" class="LineNr">389 </span>  screen-should-contain-in-color <span class="Constant">12/lightblue</span>, [
-<span id="L390" class="LineNr">390 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L391" class="LineNr">391 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L392" class="LineNr">392 </span>  <span class="Conceal">¦</span><span class="Constant"> .# de .</span>
+<span id="L372" class="LineNr">372 </span><span class="Comment"># just a little color for Mu code</span>
+<span id="L373" class="LineNr">373 </span>
+<span id="L374" class="LineNr">374 </span><span class="muScenario">scenario</span> render-colors-comments [
+<span id="L375" class="LineNr">375 </span>  <span class="Constant">local-scope</span>
+<span id="L376" class="LineNr">376 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
+<span id="L377" class="LineNr">377 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
+<span id="L378" class="LineNr">378 </span><span class="Constant"># de</span>
+<span id="L379" class="LineNr">379 </span><span class="Constant">f]</span>
+<span id="L380" class="LineNr">380 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L381" class="LineNr">381 </span>  run [
+<span id="L382" class="LineNr">382 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L383" class="LineNr">383 </span>  ]
+<span id="L384" class="LineNr">384 </span>  screen-should-contain [
+<span id="L385" class="LineNr">385 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L386" class="LineNr">386 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc  .</span>
+<span id="L387" class="LineNr">387 </span>  <span class="Conceal">¦</span><span class="Constant"> .# de .</span>
+<span id="L388" class="LineNr">388 </span>  <span class="Conceal">¦</span><span class="Constant"> .f    .</span>
+<span id="L389" class="LineNr">389 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L390" class="LineNr">390 </span>  ]
+<span id="L391" class="LineNr">391 </span>  screen-should-contain-in-color <span class="Constant">12/lightblue</span>, [
+<span id="L392" class="LineNr">392 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
 <span id="L393" class="LineNr">393 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L394" class="LineNr">394 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L395" class="LineNr">395 </span>  ]
-<span id="L396" class="LineNr">396 </span>  screen-should-contain-in-color <span class="Constant">7/white</span>, [
-<span id="L397" class="LineNr">397 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L398" class="LineNr">398 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc  .</span>
+<span id="L394" class="LineNr">394 </span>  <span class="Conceal">¦</span><span class="Constant"> .# de .</span>
+<span id="L395" class="LineNr">395 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L396" class="LineNr">396 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L397" class="LineNr">397 </span>  ]
+<span id="L398" class="LineNr">398 </span>  screen-should-contain-in-color <span class="Constant">7/white</span>, [
 <span id="L399" class="LineNr">399 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L400" class="LineNr">400 </span>  <span class="Conceal">¦</span><span class="Constant"> .f    .</span>
+<span id="L400" class="LineNr">400 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc  .</span>
 <span id="L401" class="LineNr">401 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
-<span id="L402" class="LineNr">402 </span>  ]
-<span id="L403" class="LineNr">403 </span>]
-<span id="L404" class="LineNr">404 </span>
-<span id="L405" class="LineNr">405 </span><span class="muRecipe">after</span> <span class="Constant">&lt;character-c-received&gt;</span> [
-<span id="L406" class="LineNr">406 </span>  color <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L410'>get-color</a> color, c
-<span id="L407" class="LineNr">407 </span>]
-<span id="L408" class="LineNr">408 </span>
-<span id="L409" class="LineNr">409 </span><span class="Comment"># so far the previous color is all the information we need; that may change</span>
-<span id="L410" class="LineNr">410 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L410'>get-color</a> color:num, c:char<span class="muRecipe"> -&gt; </span>color:num [
-<span id="L411" class="LineNr">411 </span>  <span class="Constant">local-scope</span>
-<span id="L412" class="LineNr">412 </span>  <span class="Constant">load-ingredients</span>
-<span id="L413" class="LineNr">413 </span>  color-is-white?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">7/white</span>
-<span id="L414" class="LineNr">414 </span>  <span class="Comment"># if color is white and next character is '#', switch color to blue</span>
-<span id="L415" class="LineNr">415 </span>  <span class="Delimiter">{</span>
-<span id="L416" class="LineNr">416 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-white?
-<span id="L417" class="LineNr">417 </span>  <span class="Conceal">¦</span> starting-comment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">35/#</span>
-<span id="L418" class="LineNr">418 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> starting-comment?
-<span id="L419" class="LineNr">419 </span>  <span class="Conceal">¦</span> trace<span class="Constant"> 90</span>, <span class="Constant">[app]</span>, <span class="Constant">[switch color back to blue]</span>
-<span id="L420" class="LineNr">420 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">12/lightblue</span>
-<span id="L421" class="LineNr">421 </span>  <span class="Delimiter">}</span>
-<span id="L422" class="LineNr">422 </span>  <span class="Comment"># if color is blue and next character is newline, switch color to white</span>
-<span id="L423" class="LineNr">423 </span>  <span class="Delimiter">{</span>
-<span id="L424" class="LineNr">424 </span>  <span class="Conceal">¦</span> color-is-blue?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">12/lightblue</span>
-<span id="L425" class="LineNr">425 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-blue?
-<span id="L426" class="LineNr">426 </span>  <span class="Conceal">¦</span> ending-comment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
-<span id="L427" class="LineNr">427 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> ending-comment?
-<span id="L428" class="LineNr">428 </span>  <span class="Conceal">¦</span> trace<span class="Constant"> 90</span>, <span class="Constant">[app]</span>, <span class="Constant">[switch color back to white]</span>
-<span id="L429" class="LineNr">429 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">7/white</span>
-<span id="L430" class="LineNr">430 </span>  <span class="Delimiter">}</span>
-<span id="L431" class="LineNr">431 </span>  <span class="Comment"># if color is white (no comments) and next character is '&lt;', switch color to red</span>
-<span id="L432" class="LineNr">432 </span>  <span class="Delimiter">{</span>
-<span id="L433" class="LineNr">433 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-white?
-<span id="L434" class="LineNr">434 </span>  <span class="Conceal">¦</span> starting-assignment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">60/&lt;</span>
-<span id="L435" class="LineNr">435 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> starting-assignment?
-<span id="L436" class="LineNr">436 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">1/red</span>
-<span id="L437" class="LineNr">437 </span>  <span class="Delimiter">}</span>
-<span id="L438" class="LineNr">438 </span>  <span class="Comment"># if color is red and next character is space, switch color to white</span>
-<span id="L439" class="LineNr">439 </span>  <span class="Delimiter">{</span>
-<span id="L440" class="LineNr">440 </span>  <span class="Conceal">¦</span> color-is-red?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">1/red</span>
-<span id="L441" class="LineNr">441 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-red?
-<span id="L442" class="LineNr">442 </span>  <span class="Conceal">¦</span> ending-assignment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">32/space</span>
-<span id="L443" class="LineNr">443 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> ending-assignment?
-<span id="L444" class="LineNr">444 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">7/white</span>
-<span id="L445" class="LineNr">445 </span>  <span class="Delimiter">}</span>
-<span id="L446" class="LineNr">446 </span>  <span class="Comment"># otherwise no change</span>
-<span id="L447" class="LineNr">447 </span>  <span class="muControl">return</span> color
-<span id="L448" class="LineNr">448 </span>]
-<span id="L449" class="LineNr">449 </span>
-<span id="L450" class="LineNr">450 </span><span class="muScenario">scenario</span> render-colors-assignment [
-<span id="L451" class="LineNr">451 </span>  <span class="Constant">local-scope</span>
-<span id="L452" class="LineNr">452 </span>  assume-screen <span class="Constant">8/width</span>, <span class="Constant">5/height</span>
-<span id="L453" class="LineNr">453 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
-<span id="L454" class="LineNr">454 </span><span class="Constant">d &lt;- e</span>
-<span id="L455" class="LineNr">455 </span><span class="Constant">f]</span>
-<span id="L456" class="LineNr">456 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
-<span id="L457" class="LineNr">457 </span>  run [
-<span id="L458" class="LineNr">458 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
-<span id="L459" class="LineNr">459 </span>  ]
-<span id="L460" class="LineNr">460 </span>  screen-should-contain [
-<span id="L461" class="LineNr">461 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
-<span id="L462" class="LineNr">462 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc     .</span>
-<span id="L463" class="LineNr">463 </span>  <span class="Conceal">¦</span><span class="Constant"> .d &lt;- e  .</span>
-<span id="L464" class="LineNr">464 </span>  <span class="Conceal">¦</span><span class="Constant"> .f       .</span>
-<span id="L465" class="LineNr">465 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
-<span id="L466" class="LineNr">466 </span>  ]
-<span id="L467" class="LineNr">467 </span>  screen-should-contain-in-color <span class="Constant">1/red</span>, [
-<span id="L468" class="LineNr">468 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
-<span id="L469" class="LineNr">469 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
-<span id="L470" class="LineNr">470 </span>  <span class="Conceal">¦</span><span class="Constant"> .  &lt;-    .</span>
+<span id="L402" class="LineNr">402 </span>  <span class="Conceal">¦</span><span class="Constant"> .f    .</span>
+<span id="L403" class="LineNr">403 </span>  <span class="Conceal">¦</span><span class="Constant"> .     .</span>
+<span id="L404" class="LineNr">404 </span>  ]
+<span id="L405" class="LineNr">405 </span>]
+<span id="L406" class="LineNr">406 </span>
+<span id="L407" class="LineNr">407 </span><span class="muRecipe">after</span> <span class="Constant">&lt;character-c-received&gt;</span> [
+<span id="L408" class="LineNr">408 </span>  color <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L412'>get-color</a> color, c
+<span id="L409" class="LineNr">409 </span>]
+<span id="L410" class="LineNr">410 </span>
+<span id="L411" class="LineNr">411 </span><span class="Comment"># so far the previous color is all the information we need; that may change</span>
+<span id="L412" class="LineNr">412 </span><span class="muRecipe">def</span> <a href='001-editor.mu.html#L412'>get-color</a> color:num, c:char<span class="muRecipe"> -&gt; </span>color:num [
+<span id="L413" class="LineNr">413 </span>  <span class="Constant">local-scope</span>
+<span id="L414" class="LineNr">414 </span>  <span class="Constant">load-ingredients</span>
+<span id="L415" class="LineNr">415 </span>  color-is-white?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">7/white</span>
+<span id="L416" class="LineNr">416 </span>  <span class="Comment"># if color is white and next character is '#', switch color to blue</span>
+<span id="L417" class="LineNr">417 </span>  <span class="Delimiter">{</span>
+<span id="L418" class="LineNr">418 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-white?
+<span id="L419" class="LineNr">419 </span>  <span class="Conceal">¦</span> starting-comment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">35/#</span>
+<span id="L420" class="LineNr">420 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> starting-comment?
+<span id="L421" class="LineNr">421 </span>  <span class="Conceal">¦</span> trace<span class="Constant"> 90</span>, <span class="Constant">[app]</span>, <span class="Constant">[switch color back to blue]</span>
+<span id="L422" class="LineNr">422 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">12/lightblue</span>
+<span id="L423" class="LineNr">423 </span>  <span class="Delimiter">}</span>
+<span id="L424" class="LineNr">424 </span>  <span class="Comment"># if color is blue and next character is newline, switch color to white</span>
+<span id="L425" class="LineNr">425 </span>  <span class="Delimiter">{</span>
+<span id="L426" class="LineNr">426 </span>  <span class="Conceal">¦</span> color-is-blue?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">12/lightblue</span>
+<span id="L427" class="LineNr">427 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-blue?
+<span id="L428" class="LineNr">428 </span>  <span class="Conceal">¦</span> ending-comment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
+<span id="L429" class="LineNr">429 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> ending-comment?
+<span id="L430" class="LineNr">430 </span>  <span class="Conceal">¦</span> trace<span class="Constant"> 90</span>, <span class="Constant">[app]</span>, <span class="Constant">[switch color back to white]</span>
+<span id="L431" class="LineNr">431 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">7/white</span>
+<span id="L432" class="LineNr">432 </span>  <span class="Delimiter">}</span>
+<span id="L433" class="LineNr">433 </span>  <span class="Comment"># if color is white (no comments) and next character is '&lt;', switch color to red</span>
+<span id="L434" class="LineNr">434 </span>  <span class="Delimiter">{</span>
+<span id="L435" class="LineNr">435 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-white?
+<span id="L436" class="LineNr">436 </span>  <span class="Conceal">¦</span> starting-assignment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">60/&lt;</span>
+<span id="L437" class="LineNr">437 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> starting-assignment?
+<span id="L438" class="LineNr">438 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">1/red</span>
+<span id="L439" class="LineNr">439 </span>  <span class="Delimiter">}</span>
+<span id="L440" class="LineNr">440 </span>  <span class="Comment"># if color is red and next character is space, switch color to white</span>
+<span id="L441" class="LineNr">441 </span>  <span class="Delimiter">{</span>
+<span id="L442" class="LineNr">442 </span>  <span class="Conceal">¦</span> color-is-red?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">1/red</span>
+<span id="L443" class="LineNr">443 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> color-is-red?
+<span id="L444" class="LineNr">444 </span>  <span class="Conceal">¦</span> ending-assignment?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">32/space</span>
+<span id="L445" class="LineNr">445 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> ending-assignment?
+<span id="L446" class="LineNr">446 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">7/white</span>
+<span id="L447" class="LineNr">447 </span>  <span class="Delimiter">}</span>
+<span id="L448" class="LineNr">448 </span>  <span class="Comment"># otherwise no change</span>
+<span id="L449" class="LineNr">449 </span>  <span class="muControl">return</span> color
+<span id="L450" class="LineNr">450 </span>]
+<span id="L451" class="LineNr">451 </span>
+<span id="L452" class="LineNr">452 </span><span class="muScenario">scenario</span> render-colors-assignment [
+<span id="L453" class="LineNr">453 </span>  <span class="Constant">local-scope</span>
+<span id="L454" class="LineNr">454 </span>  assume-screen <span class="Constant">8/width</span>, <span class="Constant">5/height</span>
+<span id="L455" class="LineNr">455 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
+<span id="L456" class="LineNr">456 </span><span class="Constant">d &lt;- e</span>
+<span id="L457" class="LineNr">457 </span><span class="Constant">f]</span>
+<span id="L458" class="LineNr">458 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
+<span id="L459" class="LineNr">459 </span>  run [
+<span id="L460" class="LineNr">460 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, e
+<span id="L461" class="LineNr">461 </span>  ]
+<span id="L462" class="LineNr">462 </span>  screen-should-contain [
+<span id="L463" class="LineNr">463 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
+<span id="L464" class="LineNr">464 </span>  <span class="Conceal">¦</span><span class="Constant"> .abc     .</span>
+<span id="L465" class="LineNr">465 </span>  <span class="Conceal">¦</span><span class="Constant"> .d &lt;- e  .</span>
+<span id="L466" class="LineNr">466 </span>  <span class="Conceal">¦</span><span class="Constant"> .f       .</span>
+<span id="L467" class="LineNr">467 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
+<span id="L468" class="LineNr">468 </span>  ]
+<span id="L469" class="LineNr">469 </span>  screen-should-contain-in-color <span class="Constant">1/red</span>, [
+<span id="L470" class="LineNr">470 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
 <span id="L471" class="LineNr">471 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
-<span id="L472" class="LineNr">472 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
-<span id="L473" class="LineNr">473 </span>  ]
-<span id="L474" class="LineNr">474 </span>]
+<span id="L472" class="LineNr">472 </span>  <span class="Conceal">¦</span><span class="Constant"> .  &lt;-    .</span>
+<span id="L473" class="LineNr">473 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
+<span id="L474" class="LineNr">474 </span>  <span class="Conceal">¦</span><span class="Constant"> .        .</span>
+<span id="L475" class="LineNr">475 </span>  ]
+<span id="L476" class="LineNr">476 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/002-typing.mu.html b/html/edit/002-typing.mu.html
index ad249e5c..29c0a77e 100644
--- a/html/edit/002-typing.mu.html
+++ b/html/edit/002-typing.mu.html
@@ -69,7 +69,7 @@ if ('onhashchange' in window) {
 <span id="L6" class="LineNr">   6 </span>  <span class="Constant">local-scope</span>
 <span id="L7" class="LineNr">   7 </span>  <span class="Constant">load-ingredients</span>
 <span id="L8" class="LineNr">   8 </span>  open-console
-<span id="L9" class="LineNr">   9 </span>  editor:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> text, <span class="Constant">5/left</span>, <span class="Constant">45/right</span>
+<span id="L9" class="LineNr">   9 </span>  editor:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> text, <span class="Constant">5/left</span>, <span class="Constant">45/right</span>
 <span id="L10" class="LineNr">  10 </span>  <a href='002-typing.mu.html#L14'>editor-event-loop</a> <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, editor
 <span id="L11" class="LineNr">  11 </span>  close-console
 <span id="L12" class="LineNr">  12 </span>]
@@ -82,7 +82,7 @@ if ('onhashchange' in window) {
 <span id="L19" class="LineNr">  19 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-event</span>
 <span id="L20" class="LineNr">  20 </span>  <span class="Conceal">¦</span> cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
 <span id="L21" class="LineNr">  21 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
-<span id="L22" class="LineNr">  22 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
+<span id="L22" class="LineNr">  22 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
 <span id="L23" class="LineNr">  23 </span>  <span class="Conceal">¦</span> e:<a href='../084console.mu.html#L4'>event</a>, found?:bool, quit?:bool, <a href='../084console.mu.html#L23'>console</a> <span class="Special">&lt;-</span> <a href='../084console.mu.html#L35'>read-event</a> <a href='../084console.mu.html#L23'>console</a>
 <span id="L24" class="LineNr">  24 </span>  <span class="Conceal">¦</span> <span class="muControl">loop-unless</span> found?
 <span id="L25" class="LineNr">  25 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> quit?  <span class="Comment"># only in tests</span>
@@ -139,7 +139,7 @@ if ('onhashchange' in window) {
 <span id="L76" class="LineNr">  76 </span>  <span class="muControl">return-unless</span> editor
 <span id="L77" class="LineNr">  77 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
 <span id="L78" class="LineNr">  78 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
-<span id="L79" class="LineNr">  79 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L79" class="LineNr">  79 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L80" class="LineNr">  80 </span>  <span class="Comment"># count newlines until screen row</span>
 <span id="L81" class="LineNr">  81 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
 <span id="L82" class="LineNr">  82 </span>  <a href='../065duplex_list.mu.html#L36'>prev</a>:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
@@ -154,7 +154,7 @@ if ('onhashchange' in window) {
 <span id="L91" class="LineNr">  91 </span>  <span class="Delimiter">{</span>
 <span id="L92" class="LineNr">  92 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
 <span id="L93" class="LineNr">  93 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
-<span id="L94" class="LineNr">  94 </span>  <span class="Conceal">¦</span> off-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L94" class="LineNr">  94 </span>  <span class="Conceal">¦</span> off-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L95" class="LineNr">  95 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> off-screen?
 <span id="L96" class="LineNr">  96 </span>  <span class="Conceal">¦</span> <span class="Comment"># update editor.before-cursor</span>
 <span id="L97" class="LineNr">  97 </span>  <span class="Conceal">¦</span> <span class="Comment"># Doing so at the start of each iteration ensures it stays one step behind</span>
@@ -228,8 +228,8 @@ if ('onhashchange' in window) {
 <span id="L165" class="LineNr"> 165 </span>  <span class="Constant">local-scope</span>
 <span id="L166" class="LineNr"> 166 </span>  <span class="Constant">load-ingredients</span>
 <span id="L167" class="LineNr"> 167 </span>  <span class="muControl">return-unless</span> editor, <span class="Constant">0/don't-render</span>
-<span id="L168" class="LineNr"> 168 </span>  <a href='../081print.mu.html#L574'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L169" class="LineNr"> 169 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L168" class="LineNr"> 168 </span>  <a href='../081print.mu.html#L581'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L169" class="LineNr"> 169 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L170" class="LineNr"> 170 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
 <span id="L171" class="LineNr"> 171 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
 <span id="L172" class="LineNr"> 172 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
@@ -274,8 +274,8 @@ if ('onhashchange' in window) {
 <span id="L211" class="LineNr"> 211 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
 <span id="L212" class="LineNr"> 212 </span>  save-row:num <span class="Special">&lt;-</span> copy cursor-row
 <span id="L213" class="LineNr"> 213 </span>  save-column:num <span class="Special">&lt;-</span> copy cursor-column
-<span id="L214" class="LineNr"> 214 </span>  <a href='../081print.mu.html#L574'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L215" class="LineNr"> 215 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L214" class="LineNr"> 214 </span>  <a href='../081print.mu.html#L581'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L215" class="LineNr"> 215 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L216" class="LineNr"> 216 </span>  <span class="Comment"># occasionally we'll need to mess with the cursor</span>
 <span id="L217" class="LineNr"> 217 </span><span class="Constant">  <a href='002-typing.mu.html#L217'>&lt;insert-character-special-case&gt;</a></span>
 <span id="L218" class="LineNr"> 218 </span>  <span class="Comment"># but mostly we'll just move the cursor right</span>
@@ -286,22 +286,22 @@ if ('onhashchange' in window) {
 <span id="L223" class="LineNr"> 223 </span>  <span class="Conceal">¦</span> <span class="Comment"># at end of all text? no need to scroll? just print the character and leave</span>
 <span id="L224" class="LineNr"> 224 </span>  <span class="Conceal">¦</span> at-end?:bool <span class="Special">&lt;-</span> equal <a href='../065duplex_list.mu.html#L29'>next</a>, <span class="Constant">0/null</span>
 <span id="L225" class="LineNr"> 225 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-end?
-<span id="L226" class="LineNr"> 226 </span>  <span class="Conceal">¦</span> bottom:num <span class="Special">&lt;-</span> subtract <a href='../081print.mu.html#L587'>screen-height</a>,<span class="Constant"> 1</span>
+<span id="L226" class="LineNr"> 226 </span>  <span class="Conceal">¦</span> bottom:num <span class="Special">&lt;-</span> subtract <a href='../081print.mu.html#L594'>screen-height</a>,<span class="Constant"> 1</span>
 <span id="L227" class="LineNr"> 227 </span>  <span class="Conceal">¦</span> at-bottom?:bool <span class="Special">&lt;-</span> equal save-row, bottom
 <span id="L228" class="LineNr"> 228 </span>  <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> equal save-column, right
 <span id="L229" class="LineNr"> 229 </span>  <span class="Conceal">¦</span> overflow?:bool <span class="Special">&lt;-</span> and at-bottom?, at-right?
 <span id="L230" class="LineNr"> 230 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> overflow?
-<span id="L231" class="LineNr"> 231 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, save-row, save-column
+<span id="L231" class="LineNr"> 231 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, save-row, save-column
 <span id="L232" class="LineNr"> 232 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c
 <span id="L233" class="LineNr"> 233 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">0/don't-render</span>
 <span id="L234" class="LineNr"> 234 </span>  <span class="Delimiter">}</span>
 <span id="L235" class="LineNr"> 235 </span>  <span class="Delimiter">{</span>
 <span id="L236" class="LineNr"> 236 </span>  <span class="Conceal">¦</span> <span class="Comment"># not at right margin? print the character and rest of line</span>
 <span id="L237" class="LineNr"> 237 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> <a href='../065duplex_list.mu.html#L29'>next</a>
-<span id="L238" class="LineNr"> 238 </span>  <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-column, <a href='../081print.mu.html#L574'>screen-width</a>
+<span id="L238" class="LineNr"> 238 </span>  <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-column, <a href='../081print.mu.html#L581'>screen-width</a>
 <span id="L239" class="LineNr"> 239 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> at-right?
 <span id="L240" class="LineNr"> 240 </span>  <span class="Conceal">¦</span> curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> copy before-cursor
-<span id="L241" class="LineNr"> 241 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, save-row, save-column
+<span id="L241" class="LineNr"> 241 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, save-row, save-column
 <span id="L242" class="LineNr"> 242 </span>  <span class="Conceal">¦</span> curr-column:num <span class="Special">&lt;-</span> copy save-column
 <span id="L243" class="LineNr"> 243 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
 <span id="L244" class="LineNr"> 244 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># hit right margin? give up and let caller render</span>
@@ -328,18 +328,18 @@ if ('onhashchange' in window) {
 <span id="L265" class="LineNr"> 265 </span>  <span class="Constant">load-ingredients</span>
 <span id="L266" class="LineNr"> 266 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
 <span id="L267" class="LineNr"> 267 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
-<span id="L268" class="LineNr"> 268 </span>  row:num, column:num <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L121'>render</a> <a href='../081print.mu.html#L4'>screen</a>, editor
-<span id="L269" class="LineNr"> 269 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L268" class="LineNr"> 268 </span>  row:num, column:num <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L123'>render</a> <a href='../081print.mu.html#L4'>screen</a>, editor
+<span id="L269" class="LineNr"> 269 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
 <span id="L270" class="LineNr"> 270 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
 <span id="L271" class="LineNr"> 271 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right, <span class="Constant">9480/horizontal-dotted</span>
 <span id="L272" class="LineNr"> 272 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L273" class="LineNr"> 273 </span>  <a href='001-editor.mu.html#L221'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, left, right
+<span id="L273" class="LineNr"> 273 </span>  <a href='001-editor.mu.html#L223'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, left, right
 <span id="L274" class="LineNr"> 274 </span>]
 <span id="L275" class="LineNr"> 275 </span>
 <span id="L276" class="LineNr"> 276 </span><span class="muScenario">scenario</span> editor-handles-empty-event-queue [
 <span id="L277" class="LineNr"> 277 </span>  <span class="Constant">local-scope</span>
 <span id="L278" class="LineNr"> 278 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L279" class="LineNr"> 279 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L279" class="LineNr"> 279 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L280" class="LineNr"> 280 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L281" class="LineNr"> 281 </span>  assume-console <span class="Constant">[]</span>
 <span id="L282" class="LineNr"> 282 </span>  run [
@@ -356,7 +356,7 @@ if ('onhashchange' in window) {
 <span id="L293" class="LineNr"> 293 </span><span class="muScenario">scenario</span> editor-handles-mouse-clicks [
 <span id="L294" class="LineNr"> 294 </span>  <span class="Constant">local-scope</span>
 <span id="L295" class="LineNr"> 295 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L296" class="LineNr"> 296 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L296" class="LineNr"> 296 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L297" class="LineNr"> 297 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L298" class="LineNr"> 298 </span>  $clear-trace
 <span id="L299" class="LineNr"> 299 </span>  assume-console [
@@ -383,7 +383,7 @@ if ('onhashchange' in window) {
 <span id="L320" class="LineNr"> 320 </span><span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text [
 <span id="L321" class="LineNr"> 321 </span>  <span class="Constant">local-scope</span>
 <span id="L322" class="LineNr"> 322 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L323" class="LineNr"> 323 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L323" class="LineNr"> 323 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L324" class="LineNr"> 324 </span>  $clear-trace
 <span id="L325" class="LineNr"> 325 </span>  assume-console [
 <span id="L326" class="LineNr"> 326 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 7</span>  <span class="Comment"># last line, to the right of text</span>
@@ -405,7 +405,7 @@ if ('onhashchange' in window) {
 <span id="L342" class="LineNr"> 342 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L343" class="LineNr"> 343 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L344" class="LineNr"> 344 </span><span class="Constant">def]</span>
-<span id="L345" class="LineNr"> 345 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L345" class="LineNr"> 345 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L346" class="LineNr"> 346 </span>  $clear-trace
 <span id="L347" class="LineNr"> 347 </span>  assume-console [
 <span id="L348" class="LineNr"> 348 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 7</span>  <span class="Comment"># interior line, to the right of text</span>
@@ -427,7 +427,7 @@ if ('onhashchange' in window) {
 <span id="L364" class="LineNr"> 364 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L365" class="LineNr"> 365 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L366" class="LineNr"> 366 </span><span class="Constant">def]</span>
-<span id="L367" class="LineNr"> 367 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L367" class="LineNr"> 367 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L368" class="LineNr"> 368 </span>  $clear-trace
 <span id="L369" class="LineNr"> 369 </span>  assume-console [
 <span id="L370" class="LineNr"> 370 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 7</span>  <span class="Comment"># below text</span>
@@ -448,7 +448,7 @@ if ('onhashchange' in window) {
 <span id="L385" class="LineNr"> 385 </span>  <span class="Constant">local-scope</span>
 <span id="L386" class="LineNr"> 386 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L387" class="LineNr"> 387 </span>  <span class="Comment"># editor occupies only left half of screen</span>
-<span id="L388" class="LineNr"> 388 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L388" class="LineNr"> 388 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L389" class="LineNr"> 389 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L390" class="LineNr"> 390 </span>  $clear-trace
 <span id="L391" class="LineNr"> 391 </span>  assume-console [
@@ -476,7 +476,7 @@ if ('onhashchange' in window) {
 <span id="L413" class="LineNr"> 413 </span><span class="muScenario">scenario</span> editor-handles-mouse-clicks-in-menu-area [
 <span id="L414" class="LineNr"> 414 </span>  <span class="Constant">local-scope</span>
 <span id="L415" class="LineNr"> 415 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L416" class="LineNr"> 416 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L416" class="LineNr"> 416 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L417" class="LineNr"> 417 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L418" class="LineNr"> 418 </span>  $clear-trace
 <span id="L419" class="LineNr"> 419 </span>  assume-console [
@@ -498,7 +498,7 @@ if ('onhashchange' in window) {
 <span id="L435" class="LineNr"> 435 </span><span class="muScenario">scenario</span> editor-inserts-characters-into-empty-editor [
 <span id="L436" class="LineNr"> 436 </span>  <span class="Constant">local-scope</span>
 <span id="L437" class="LineNr"> 437 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L438" class="LineNr"> 438 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L438" class="LineNr"> 438 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L439" class="LineNr"> 439 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L440" class="LineNr"> 440 </span>  $clear-trace
 <span id="L441" class="LineNr"> 441 </span>  assume-console [
@@ -519,7 +519,7 @@ if ('onhashchange' in window) {
 <span id="L456" class="LineNr"> 456 </span><span class="muScenario">scenario</span> editor-inserts-characters-at-cursor [
 <span id="L457" class="LineNr"> 457 </span>  <span class="Constant">local-scope</span>
 <span id="L458" class="LineNr"> 458 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L459" class="LineNr"> 459 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L459" class="LineNr"> 459 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L460" class="LineNr"> 460 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L461" class="LineNr"> 461 </span>  $clear-trace
 <span id="L462" class="LineNr"> 462 </span>  <span class="Comment"># type two letters at different places</span>
@@ -543,7 +543,7 @@ if ('onhashchange' in window) {
 <span id="L480" class="LineNr"> 480 </span><span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-2 [
 <span id="L481" class="LineNr"> 481 </span>  <span class="Constant">local-scope</span>
 <span id="L482" class="LineNr"> 482 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L483" class="LineNr"> 483 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L483" class="LineNr"> 483 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L484" class="LineNr"> 484 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L485" class="LineNr"> 485 </span>  $clear-trace
 <span id="L486" class="LineNr"> 486 </span>  assume-console [
@@ -567,7 +567,7 @@ if ('onhashchange' in window) {
 <span id="L504" class="LineNr"> 504 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L505" class="LineNr"> 505 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L506" class="LineNr"> 506 </span><span class="Constant">d]</span>
-<span id="L507" class="LineNr"> 507 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L507" class="LineNr"> 507 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L508" class="LineNr"> 508 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L509" class="LineNr"> 509 </span>  $clear-trace
 <span id="L510" class="LineNr"> 510 </span>  assume-console [
@@ -590,7 +590,7 @@ if ('onhashchange' in window) {
 <span id="L527" class="LineNr"> 527 </span><span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-3 [
 <span id="L528" class="LineNr"> 528 </span>  <span class="Constant">local-scope</span>
 <span id="L529" class="LineNr"> 529 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L530" class="LineNr"> 530 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L530" class="LineNr"> 530 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L531" class="LineNr"> 531 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L532" class="LineNr"> 532 </span>  $clear-trace
 <span id="L533" class="LineNr"> 533 </span>  assume-console [
@@ -614,7 +614,7 @@ if ('onhashchange' in window) {
 <span id="L551" class="LineNr"> 551 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L552" class="LineNr"> 552 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L553" class="LineNr"> 553 </span><span class="Constant">d]</span>
-<span id="L554" class="LineNr"> 554 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L554" class="LineNr"> 554 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L555" class="LineNr"> 555 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L556" class="LineNr"> 556 </span>  $clear-trace
 <span id="L557" class="LineNr"> 557 </span>  assume-console [
@@ -639,7 +639,7 @@ if ('onhashchange' in window) {
 <span id="L576" class="LineNr"> 576 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L577" class="LineNr"> 577 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L578" class="LineNr"> 578 </span><span class="Constant">d]</span>
-<span id="L579" class="LineNr"> 579 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L579" class="LineNr"> 579 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L580" class="LineNr"> 580 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L581" class="LineNr"> 581 </span>  $clear-trace
 <span id="L582" class="LineNr"> 582 </span>  assume-console [
@@ -662,7 +662,7 @@ if ('onhashchange' in window) {
 <span id="L599" class="LineNr"> 599 </span><span class="muScenario">scenario</span> editor-moves-cursor-after-inserting-characters [
 <span id="L600" class="LineNr"> 600 </span>  <span class="Constant">local-scope</span>
 <span id="L601" class="LineNr"> 601 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L602" class="LineNr"> 602 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[ab]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L602" class="LineNr"> 602 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[ab]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L603" class="LineNr"> 603 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L604" class="LineNr"> 604 </span>  assume-console [
 <span id="L605" class="LineNr"> 605 </span>  <span class="Conceal">¦</span> type <span class="Constant">[01]</span>
@@ -683,7 +683,7 @@ if ('onhashchange' in window) {
 <span id="L620" class="LineNr"> 620 </span><span class="muScenario">scenario</span> editor-wraps-line-on-insert [
 <span id="L621" class="LineNr"> 621 </span>  <span class="Constant">local-scope</span>
 <span id="L622" class="LineNr"> 622 </span>  assume-screen <span class="Constant">5/width</span>, <span class="Constant">5/height</span>
-<span id="L623" class="LineNr"> 623 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L623" class="LineNr"> 623 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L624" class="LineNr"> 624 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L625" class="LineNr"> 625 </span>  <span class="Comment"># type a letter</span>
 <span id="L626" class="LineNr"> 626 </span>  assume-console [
@@ -723,7 +723,7 @@ if ('onhashchange' in window) {
 <span id="L660" class="LineNr"> 660 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L661" class="LineNr"> 661 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abcdefg</span>
 <span id="L662" class="LineNr"> 662 </span><span class="Constant">defg]</span>
-<span id="L663" class="LineNr"> 663 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L663" class="LineNr"> 663 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L664" class="LineNr"> 664 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L665" class="LineNr"> 665 </span>  <span class="Comment"># type more text at the start</span>
 <span id="L666" class="LineNr"> 666 </span>  assume-console [
@@ -792,7 +792,7 @@ if ('onhashchange' in window) {
 <span id="L729" class="LineNr"> 729 </span>  <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
 <span id="L730" class="LineNr"> 730 </span>  <span class="Conceal">¦</span> <span class="Comment"># if we're out of the screen, scroll down</span>
 <span id="L731" class="LineNr"> 731 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L732" class="LineNr"> 732 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L732" class="LineNr"> 732 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L733" class="LineNr"> 733 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> below-screen?
 <span id="L734" class="LineNr"> 734 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> &lt;scroll-down&gt;</span>
 <span id="L735" class="LineNr"> 735 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
@@ -803,7 +803,7 @@ if ('onhashchange' in window) {
 <span id="L740" class="LineNr"> 740 </span><span class="muScenario">scenario</span> editor-wraps-cursor-after-inserting-characters-in-middle-of-line [
 <span id="L741" class="LineNr"> 741 </span>  <span class="Constant">local-scope</span>
 <span id="L742" class="LineNr"> 742 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L743" class="LineNr"> 743 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L743" class="LineNr"> 743 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L744" class="LineNr"> 744 </span>  assume-console [
 <span id="L745" class="LineNr"> 745 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 3</span>  <span class="Comment"># right before the wrap icon</span>
 <span id="L746" class="LineNr"> 746 </span>  <span class="Conceal">¦</span> type <span class="Constant">[f]</span>
@@ -832,7 +832,7 @@ if ('onhashchange' in window) {
 <span id="L769" class="LineNr"> 769 </span>  <span class="Comment"># create an editor containing two lines</span>
 <span id="L770" class="LineNr"> 770 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L771" class="LineNr"> 771 </span><span class="Constant">xyz]</span>
-<span id="L772" class="LineNr"> 772 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L772" class="LineNr"> 772 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L773" class="LineNr"> 773 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L774" class="LineNr"> 774 </span>  screen-should-contain [
 <span id="L775" class="LineNr"> 775 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -860,7 +860,7 @@ if ('onhashchange' in window) {
 <span id="L797" class="LineNr"> 797 </span><span class="muScenario">scenario</span> editor-wraps-cursor-to-left-margin [
 <span id="L798" class="LineNr"> 798 </span>  <span class="Constant">local-scope</span>
 <span id="L799" class="LineNr"> 799 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L800" class="LineNr"> 800 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">2/left</span>, <span class="Constant">7/right</span>
+<span id="L800" class="LineNr"> 800 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">2/left</span>, <span class="Constant">7/right</span>
 <span id="L801" class="LineNr"> 801 </span>  assume-console [
 <span id="L802" class="LineNr"> 802 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 5</span>  <span class="Comment"># line is full; no wrap icon yet</span>
 <span id="L803" class="LineNr"> 803 </span>  <span class="Conceal">¦</span> type <span class="Constant">[01]</span>
@@ -889,14 +889,14 @@ if ('onhashchange' in window) {
 <span id="L826" class="LineNr"> 826 </span>  indent?:bool
 <span id="L827" class="LineNr"> 827 </span>]
 <span id="L828" class="LineNr"> 828 </span>
-<span id="L829" class="LineNr"> 829 </span><span class="muRecipe">after</span> <span class="Constant"><a href='001-editor.mu.html#L68'>&lt;editor-initialization&gt;</a></span> [
+<span id="L829" class="LineNr"> 829 </span><span class="muRecipe">after</span> <span class="Constant"><a href='001-editor.mu.html#L70'>&lt;editor-initialization&gt;</a></span> [
 <span id="L830" class="LineNr"> 830 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">indent?:offset</span>, <span class="Constant">1/true</span>
 <span id="L831" class="LineNr"> 831 </span>]
 <span id="L832" class="LineNr"> 832 </span>
 <span id="L833" class="LineNr"> 833 </span><span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline [
 <span id="L834" class="LineNr"> 834 </span>  <span class="Constant">local-scope</span>
 <span id="L835" class="LineNr"> 835 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L836" class="LineNr"> 836 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L836" class="LineNr"> 836 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L837" class="LineNr"> 837 </span>  assume-console [
 <span id="L838" class="LineNr"> 838 </span>  <span class="Conceal">¦</span> type <span class="Constant">[0</span>
 <span id="L839" class="LineNr"> 839 </span><span class="Constant">1]</span>
@@ -932,7 +932,7 @@ if ('onhashchange' in window) {
 <span id="L869" class="LineNr"> 869 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
 <span id="L870" class="LineNr"> 870 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
 <span id="L871" class="LineNr"> 871 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
-<span id="L872" class="LineNr"> 872 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L872" class="LineNr"> 872 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L873" class="LineNr"> 873 </span>  <span class="Comment"># insert newline</span>
 <span id="L874" class="LineNr"> 874 </span>  insert <span class="Constant">10/newline</span>, before-cursor
 <span id="L875" class="LineNr"> 875 </span>  before-cursor <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> before-cursor
@@ -943,7 +943,7 @@ if ('onhashchange' in window) {
 <span id="L880" class="LineNr"> 880 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
 <span id="L881" class="LineNr"> 881 </span>  <span class="Comment"># maybe scroll</span>
 <span id="L882" class="LineNr"> 882 </span>  <span class="Delimiter">{</span>
-<span id="L883" class="LineNr"> 883 </span>  <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L587'>screen-height</a>  <span class="Comment"># must be equal, never greater</span>
+<span id="L883" class="LineNr"> 883 </span>  <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L594'>screen-height</a>  <span class="Comment"># must be equal, never greater</span>
 <span id="L884" class="LineNr"> 884 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> below-screen?
 <span id="L885" class="LineNr"> 885 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;scroll-down&gt;</span>
 <span id="L886" class="LineNr"> 886 </span>  <span class="Conceal">¦</span> cursor-row <span class="Special">&lt;-</span> subtract cursor-row,<span class="Constant"> 1</span>  <span class="Comment"># bring back into screen range</span>
@@ -1000,7 +1000,7 @@ if ('onhashchange' in window) {
 <span id="L937" class="LineNr"> 937 </span><span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline-2 [
 <span id="L938" class="LineNr"> 938 </span>  <span class="Constant">local-scope</span>
 <span id="L939" class="LineNr"> 939 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L940" class="LineNr"> 940 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
+<span id="L940" class="LineNr"> 940 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
 <span id="L941" class="LineNr"> 941 </span>  assume-console [
 <span id="L942" class="LineNr"> 942 </span>  <span class="Conceal">¦</span> type <span class="Constant">[0</span>
 <span id="L943" class="LineNr"> 943 </span><span class="Constant">1]</span>
@@ -1020,7 +1020,7 @@ if ('onhashchange' in window) {
 <span id="L957" class="LineNr"> 957 </span><span class="muScenario">scenario</span> editor-clears-previous-line-completely-after-inserting-newline [
 <span id="L958" class="LineNr"> 958 </span>  <span class="Constant">local-scope</span>
 <span id="L959" class="LineNr"> 959 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L960" class="LineNr"> 960 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L960" class="LineNr"> 960 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L961" class="LineNr"> 961 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L962" class="LineNr"> 962 </span>  screen-should-contain [
 <span id="L963" class="LineNr"> 963 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -1051,7 +1051,7 @@ if ('onhashchange' in window) {
 <span id="L988" class="LineNr"> 988 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[ab</span>
 <span id="L989" class="LineNr"> 989 </span><span class="Constant">  cd</span>
 <span id="L990" class="LineNr"> 990 </span><span class="Constant">ef]</span>
-<span id="L991" class="LineNr"> 991 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L991" class="LineNr"> 991 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L992" class="LineNr"> 992 </span>  <span class="Comment"># position cursor after 'cd' and hit 'newline'</span>
 <span id="L993" class="LineNr"> 993 </span>  assume-console [
 <span id="L994" class="LineNr"> 994 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 8</span>
@@ -1076,7 +1076,7 @@ if ('onhashchange' in window) {
 <span id="L1013" class="LineNr">1013 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[ab</span>
 <span id="L1014" class="LineNr">1014 </span><span class="Constant">  cd</span>
 <span id="L1015" class="LineNr">1015 </span><span class="Constant">ef]</span>
-<span id="L1016" class="LineNr">1016 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1016" class="LineNr">1016 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1017" class="LineNr">1017 </span>  <span class="Comment"># position cursor after 'cd' and hit 'newline' surrounded by paste markers</span>
 <span id="L1018" class="LineNr">1018 </span>  assume-console [
 <span id="L1019" class="LineNr">1019 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 8</span>
@@ -1135,7 +1135,7 @@ if ('onhashchange' in window) {
 <span id="L1072" class="LineNr">1072 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> bg-color-found?
 <span id="L1073" class="LineNr">1073 </span>  <span class="Conceal">¦</span> bg-color <span class="Special">&lt;-</span> copy <span class="Constant">0/black</span>
 <span id="L1074" class="LineNr">1074 </span>  <span class="Delimiter">}</span>
-<span id="L1075" class="LineNr">1075 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, x
+<span id="L1075" class="LineNr">1075 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, x
 <span id="L1076" class="LineNr">1076 </span>  <span class="Delimiter">{</span>
 <span id="L1077" class="LineNr">1077 </span>  <span class="Conceal">¦</span> continue?:bool <span class="Special">&lt;-</span> lesser-or-equal x, right  <span class="Comment"># right is inclusive, to match editor semantics</span>
 <span id="L1078" class="LineNr">1078 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> continue?
diff --git a/html/edit/003-shortcuts.mu.html b/html/edit/003-shortcuts.mu.html
index 83871010..8e3bc675 100644
--- a/html/edit/003-shortcuts.mu.html
+++ b/html/edit/003-shortcuts.mu.html
@@ -72,7 +72,7 @@ if ('onhashchange' in window) {
 <span id="L10" class="LineNr">  10 </span>  <span class="Comment"># just one character in final line</span>
 <span id="L11" class="LineNr">  11 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[ab</span>
 <span id="L12" class="LineNr">  12 </span><span class="Constant">cd]</span>
-<span id="L13" class="LineNr">  13 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L13" class="LineNr">  13 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L14" class="LineNr">  14 </span>  assume-console [
 <span id="L15" class="LineNr">  15 </span>  <span class="Conceal">¦</span> press tab
 <span id="L16" class="LineNr">  16 </span>  ]
@@ -103,7 +103,7 @@ if ('onhashchange' in window) {
 <span id="L41" class="LineNr">  41 </span><span class="muScenario">scenario</span> editor-handles-backspace-key [
 <span id="L42" class="LineNr">  42 </span>  <span class="Constant">local-scope</span>
 <span id="L43" class="LineNr">  43 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L44" class="LineNr">  44 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L44" class="LineNr">  44 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L45" class="LineNr">  45 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L46" class="LineNr">  46 </span>  $clear-trace
 <span id="L47" class="LineNr">  47 </span>  assume-console [
@@ -158,7 +158,7 @@ if ('onhashchange' in window) {
 <span id="L96" class="LineNr">  96 </span>  before-cursor <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L36'>prev</a>
 <span id="L97" class="LineNr">  97 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, before-cursor
 <span id="L98" class="LineNr">  98 </span>  <span class="muControl">return-if</span> scroll?, <span class="Constant">1/go-render</span>
-<span id="L99" class="LineNr">  99 </span>  <a href='../081print.mu.html#L574'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L99" class="LineNr">  99 </span>  <a href='../081print.mu.html#L581'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L100" class="LineNr"> 100 </span>  cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
 <span id="L101" class="LineNr"> 101 </span>  cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
 <span id="L102" class="LineNr"> 102 </span>  <span class="Comment"># did we just backspace over a newline?</span>
@@ -167,7 +167,7 @@ if ('onhashchange' in window) {
 <span id="L105" class="LineNr"> 105 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
 <span id="L106" class="LineNr"> 106 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
 <span id="L107" class="LineNr"> 107 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> before-cursor
-<span id="L108" class="LineNr"> 108 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
+<span id="L108" class="LineNr"> 108 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
 <span id="L109" class="LineNr"> 109 </span>  curr-column:num <span class="Special">&lt;-</span> copy cursor-column
 <span id="L110" class="LineNr"> 110 </span>  <span class="Delimiter">{</span>
 <span id="L111" class="LineNr"> 111 </span>  <span class="Conceal">¦</span> <span class="Comment"># hit right margin? give up and let caller render</span>
@@ -278,7 +278,7 @@ if ('onhashchange' in window) {
 <span id="L216" class="LineNr"> 216 </span>  <span class="Comment"># just one character in final line</span>
 <span id="L217" class="LineNr"> 217 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[ab</span>
 <span id="L218" class="LineNr"> 218 </span><span class="Constant">cd]</span>
-<span id="L219" class="LineNr"> 219 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L219" class="LineNr"> 219 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L220" class="LineNr"> 220 </span>  assume-console [
 <span id="L221" class="LineNr"> 221 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 0</span>  <span class="Comment"># cursor at only character in final line</span>
 <span id="L222" class="LineNr"> 222 </span>  <span class="Conceal">¦</span> press backspace
@@ -306,7 +306,7 @@ if ('onhashchange' in window) {
 <span id="L244" class="LineNr"> 244 </span>  <span class="Comment"># initialize editor with two long-ish but non-wrapping lines</span>
 <span id="L245" class="LineNr"> 245 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc def</span>
 <span id="L246" class="LineNr"> 246 </span><span class="Constant">ghi jkl]</span>
-<span id="L247" class="LineNr"> 247 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L247" class="LineNr"> 247 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L248" class="LineNr"> 248 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L249" class="LineNr"> 249 </span>  $clear-trace
 <span id="L250" class="LineNr"> 250 </span>  <span class="Comment"># position the cursor at the start of the second and hit backspace</span>
@@ -331,7 +331,7 @@ if ('onhashchange' in window) {
 <span id="L269" class="LineNr"> 269 </span>  <span class="Constant">local-scope</span>
 <span id="L270" class="LineNr"> 270 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L271" class="LineNr"> 271 </span>  <span class="Comment"># initialize editor in part of the screen with a long line</span>
-<span id="L272" class="LineNr"> 272 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc def ghij]</span>, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
+<span id="L272" class="LineNr"> 272 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc def ghij]</span>, <span class="Constant">0/left</span>, <span class="Constant">8/right</span>
 <span id="L273" class="LineNr"> 273 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L274" class="LineNr"> 274 </span>  <span class="Comment"># confirm that it wraps</span>
 <span id="L275" class="LineNr"> 275 </span>  screen-should-contain [
@@ -364,7 +364,7 @@ if ('onhashchange' in window) {
 <span id="L302" class="LineNr"> 302 </span><span class="muScenario">scenario</span> editor-handles-delete-key [
 <span id="L303" class="LineNr"> 303 </span>  <span class="Constant">local-scope</span>
 <span id="L304" class="LineNr"> 304 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L305" class="LineNr"> 305 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L305" class="LineNr"> 305 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L306" class="LineNr"> 306 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L307" class="LineNr"> 307 </span>  $clear-trace
 <span id="L308" class="LineNr"> 308 </span>  assume-console [
@@ -422,12 +422,12 @@ if ('onhashchange' in window) {
 <span id="L360" class="LineNr"> 360 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> before-cursor  <span class="Comment"># refresh after remove above</span>
 <span id="L361" class="LineNr"> 361 </span>  cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
 <span id="L362" class="LineNr"> 362 </span>  cursor-column:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-column:offset</span>
-<span id="L363" class="LineNr"> 363 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
+<span id="L363" class="LineNr"> 363 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
 <span id="L364" class="LineNr"> 364 </span>  curr-column:num <span class="Special">&lt;-</span> copy cursor-column
-<span id="L365" class="LineNr"> 365 </span>  <a href='../081print.mu.html#L574'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L365" class="LineNr"> 365 </span>  <a href='../081print.mu.html#L581'>screen-width</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L366" class="LineNr"> 366 </span>  <span class="Delimiter">{</span>
 <span id="L367" class="LineNr"> 367 </span>  <span class="Conceal">¦</span> <span class="Comment"># hit right margin? give up and let caller render</span>
-<span id="L368" class="LineNr"> 368 </span>  <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> greater-or-equal curr-column, <a href='../081print.mu.html#L574'>screen-width</a>
+<span id="L368" class="LineNr"> 368 </span>  <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> greater-or-equal curr-column, <a href='../081print.mu.html#L581'>screen-width</a>
 <span id="L369" class="LineNr"> 369 </span>  <span class="Conceal">¦</span> <span class="muControl">return-if</span> at-right?, <span class="Constant">1/go-render</span>
 <span id="L370" class="LineNr"> 370 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
 <span id="L371" class="LineNr"> 371 </span>  <span class="Conceal">¦</span> <span class="Comment"># newline? done.</span>
@@ -450,7 +450,7 @@ if ('onhashchange' in window) {
 <span id="L388" class="LineNr"> 388 </span><span class="muScenario">scenario</span> editor-moves-cursor-right-with-key [
 <span id="L389" class="LineNr"> 389 </span>  <span class="Constant">local-scope</span>
 <span id="L390" class="LineNr"> 390 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L391" class="LineNr"> 391 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L391" class="LineNr"> 391 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L392" class="LineNr"> 392 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L393" class="LineNr"> 393 </span>  $clear-trace
 <span id="L394" class="LineNr"> 394 </span>  assume-console [
@@ -480,15 +480,15 @@ if ('onhashchange' in window) {
 <span id="L418" class="LineNr"> 418 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-begin&gt;</span>
 <span id="L419" class="LineNr"> 419 </span>  <span class="Conceal">¦</span> before-cursor <span class="Special">&lt;-</span> copy next-cursor
 <span id="L420" class="LineNr"> 420 </span>  <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, before-cursor
-<span id="L421" class="LineNr"> 421 </span>  <span class="Conceal">¦</span> go-render?:bool <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L429'>move-cursor-coordinates-right</a> editor, <a href='../081print.mu.html#L587'>screen-height</a>
-<span id="L422" class="LineNr"> 422 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
+<span id="L421" class="LineNr"> 421 </span>  <span class="Conceal">¦</span> go-render?:bool <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L429'>move-cursor-coordinates-right</a> editor, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L422" class="LineNr"> 422 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
 <span id="L423" class="LineNr"> 423 </span>  <span class="Conceal">¦</span> undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">2/right-arrow</span>
 <span id="L424" class="LineNr"> 424 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-end&gt;</span>
 <span id="L425" class="LineNr"> 425 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
 <span id="L426" class="LineNr"> 426 </span>  <span class="Delimiter">}</span>
 <span id="L427" class="LineNr"> 427 </span>]
 <span id="L428" class="LineNr"> 428 </span>
-<span id="L429" class="LineNr"> 429 </span><span class="muRecipe">def</span> <a href='003-shortcuts.mu.html#L429'>move-cursor-coordinates-right</a> editor:&amp;:editor, <a href='../081print.mu.html#L587'>screen-height</a>:num<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
+<span id="L429" class="LineNr"> 429 </span><span class="muRecipe">def</span> <a href='003-shortcuts.mu.html#L429'>move-cursor-coordinates-right</a> editor:&amp;:editor, <a href='../081print.mu.html#L594'>screen-height</a>:num<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
 <span id="L430" class="LineNr"> 430 </span>  <span class="Constant">local-scope</span>
 <span id="L431" class="LineNr"> 431 </span>  <span class="Constant">load-ingredients</span>
 <span id="L432" class="LineNr"> 432 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor <span class="Constant">before-cursor:offset</span>
@@ -505,7 +505,7 @@ if ('onhashchange' in window) {
 <span id="L443" class="LineNr"> 443 </span>  <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
 <span id="L444" class="LineNr"> 444 </span>  <span class="Conceal">¦</span> cursor-column <span class="Special">&lt;-</span> copy left
 <span id="L445" class="LineNr"> 445 </span>  <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
-<span id="L446" class="LineNr"> 446 </span>  <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L587'>screen-height</a>  <span class="Comment"># must be equal</span>
+<span id="L446" class="LineNr"> 446 </span>  <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L594'>screen-height</a>  <span class="Comment"># must be equal</span>
 <span id="L447" class="LineNr"> 447 </span>  <span class="Conceal">¦</span> <span class="muControl">return-unless</span> below-screen?, <span class="Constant">0/don't-render</span>
 <span id="L448" class="LineNr"> 448 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;scroll-down&gt;</span>
 <span id="L449" class="LineNr"> 449 </span>  <span class="Conceal">¦</span> cursor-row <span class="Special">&lt;-</span> subtract cursor-row,<span class="Constant"> 1</span>  <span class="Comment"># bring back into screen range</span>
@@ -528,7 +528,7 @@ if ('onhashchange' in window) {
 <span id="L466" class="LineNr"> 466 </span>  <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, cursor-row
 <span id="L467" class="LineNr"> 467 </span>  <span class="Conceal">¦</span> cursor-column <span class="Special">&lt;-</span> copy left
 <span id="L468" class="LineNr"> 468 </span>  <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, cursor-column
-<span id="L469" class="LineNr"> 469 </span>  <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L587'>screen-height</a>  <span class="Comment"># must be equal</span>
+<span id="L469" class="LineNr"> 469 </span>  <span class="Conceal">¦</span> below-screen?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, <a href='../081print.mu.html#L594'>screen-height</a>  <span class="Comment"># must be equal</span>
 <span id="L470" class="LineNr"> 470 </span>  <span class="Conceal">¦</span> <span class="muControl">return-unless</span> below-screen?, <span class="Constant">0/no-more-render</span>
 <span id="L471" class="LineNr"> 471 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;scroll-down&gt;</span>
 <span id="L472" class="LineNr"> 472 </span>  <span class="Conceal">¦</span> cursor-row <span class="Special">&lt;-</span> subtract cursor-row,<span class="Constant"> 1</span>  <span class="Comment"># bring back into screen range</span>
@@ -546,7 +546,7 @@ if ('onhashchange' in window) {
 <span id="L484" class="LineNr"> 484 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L485" class="LineNr"> 485 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L486" class="LineNr"> 486 </span><span class="Constant">d]</span>
-<span id="L487" class="LineNr"> 487 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L487" class="LineNr"> 487 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L488" class="LineNr"> 488 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L489" class="LineNr"> 489 </span>  $clear-trace
 <span id="L490" class="LineNr"> 490 </span>  <span class="Comment"># type right-arrow a few times to get to start of second line</span>
@@ -582,7 +582,7 @@ if ('onhashchange' in window) {
 <span id="L520" class="LineNr"> 520 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L521" class="LineNr"> 521 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L522" class="LineNr"> 522 </span><span class="Constant">d]</span>
-<span id="L523" class="LineNr"> 523 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
+<span id="L523" class="LineNr"> 523 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">1/left</span>, <span class="Constant">10/right</span>
 <span id="L524" class="LineNr"> 524 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L525" class="LineNr"> 525 </span>  assume-console [
 <span id="L526" class="LineNr"> 526 </span>  <span class="Conceal">¦</span> press right-arrow
@@ -606,7 +606,7 @@ if ('onhashchange' in window) {
 <span id="L544" class="LineNr"> 544 </span><span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow [
 <span id="L545" class="LineNr"> 545 </span>  <span class="Constant">local-scope</span>
 <span id="L546" class="LineNr"> 546 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L547" class="LineNr"> 547 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcdef]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L547" class="LineNr"> 547 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcdef]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L548" class="LineNr"> 548 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L549" class="LineNr"> 549 </span>  $clear-trace
 <span id="L550" class="LineNr"> 550 </span>  assume-console [
@@ -636,7 +636,7 @@ if ('onhashchange' in window) {
 <span id="L574" class="LineNr"> 574 </span>  <span class="Constant">local-scope</span>
 <span id="L575" class="LineNr"> 575 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L576" class="LineNr"> 576 </span>  <span class="Comment"># line just barely wrapping</span>
-<span id="L577" class="LineNr"> 577 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L577" class="LineNr"> 577 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcde]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L578" class="LineNr"> 578 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L579" class="LineNr"> 579 </span>  $clear-trace
 <span id="L580" class="LineNr"> 580 </span>  <span class="Comment"># position cursor at last character before wrap and hit right-arrow</span>
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-<span id="L613" class="LineNr"> 613 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcdef]</span>, <span class="Constant">1/left</span>, <span class="Constant">6/right</span>
+<span id="L613" class="LineNr"> 613 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcdef]</span>, <span class="Constant">1/left</span>, <span class="Constant">6/right</span>
 <span id="L614" class="LineNr"> 614 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L615" class="LineNr"> 615 </span>  $clear-trace
 <span id="L616" class="LineNr"> 616 </span>  assume-console [
@@ -703,7 +703,7 @@ if ('onhashchange' in window) {
 <span id="L641" class="LineNr"> 641 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L642" class="LineNr"> 642 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L643" class="LineNr"> 643 </span><span class="Constant">d]</span>
-<span id="L644" class="LineNr"> 644 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L644" class="LineNr"> 644 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L645" class="LineNr"> 645 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L646" class="LineNr"> 646 </span>  $clear-trace
 <span id="L647" class="LineNr"> 647 </span>  <span class="Comment"># move to end of line, press right-arrow, type a character</span>
@@ -733,7 +733,7 @@ if ('onhashchange' in window) {
 <span id="L671" class="LineNr"> 671 </span><span class="muScenario">scenario</span> editor-moves-cursor-left-with-key [
 <span id="L672" class="LineNr"> 672 </span>  <span class="Constant">local-scope</span>
 <span id="L673" class="LineNr"> 673 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L674" class="LineNr"> 674 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L674" class="LineNr"> 674 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L675" class="LineNr"> 675 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L676" class="LineNr"> 676 </span>  $clear-trace
 <span id="L677" class="LineNr"> 677 </span>  assume-console [
@@ -777,7 +777,7 @@ if ('onhashchange' in window) {
 <span id="L715" class="LineNr"> 715 </span>  <span class="Comment"># initialize editor with two lines</span>
 <span id="L716" class="LineNr"> 716 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L717" class="LineNr"> 717 </span><span class="Constant">d]</span>
-<span id="L718" class="LineNr"> 718 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L718" class="LineNr"> 718 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L719" class="LineNr"> 719 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L720" class="LineNr"> 720 </span>  $clear-trace
 <span id="L721" class="LineNr"> 721 </span>  <span class="Comment"># position cursor at start of second line (so there's no previous newline)</span>
@@ -804,7 +804,7 @@ if ('onhashchange' in window) {
 <span id="L742" class="LineNr"> 742 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L743" class="LineNr"> 743 </span><span class="Constant">def</span>
 <span id="L744" class="LineNr"> 744 </span><span class="Constant">g]</span>
-<span id="L745" class="LineNr"> 745 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s:text, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L745" class="LineNr"> 745 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s:text, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L746" class="LineNr"> 746 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L747" class="LineNr"> 747 </span>  $clear-trace
 <span id="L748" class="LineNr"> 748 </span>  <span class="Comment"># position cursor further down (so there's a newline before the character at</span>
@@ -833,7 +833,7 @@ if ('onhashchange' in window) {
 <span id="L771" class="LineNr"> 771 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L772" class="LineNr"> 772 </span><span class="Constant">def</span>
 <span id="L773" class="LineNr"> 773 </span><span class="Constant">g]</span>
-<span id="L774" class="LineNr"> 774 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L774" class="LineNr"> 774 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L775" class="LineNr"> 775 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L776" class="LineNr"> 776 </span>  $clear-trace
 <span id="L777" class="LineNr"> 777 </span>  <span class="Comment"># position cursor at start of text, press left-arrow, then type a character</span>
@@ -863,7 +863,7 @@ if ('onhashchange' in window) {
 <span id="L801" class="LineNr"> 801 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L802" class="LineNr"> 802 </span>
 <span id="L803" class="LineNr"> 803 </span>d]
-<span id="L804" class="LineNr"> 804 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L804" class="LineNr"> 804 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L805" class="LineNr"> 805 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e:&amp;:editor
 <span id="L806" class="LineNr"> 806 </span>  $clear-trace
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@@ -889,7 +889,7 @@ if ('onhashchange' in window) {
 <span id="L827" class="LineNr"> 827 </span>  <span class="Constant">local-scope</span>
 <span id="L828" class="LineNr"> 828 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
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-<span id="L830" class="LineNr"> 830 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[abcdef]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L830" class="LineNr"> 830 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abcdef]</span>, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L831" class="LineNr"> 831 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L832" class="LineNr"> 832 </span>  $clear-trace
 <span id="L833" class="LineNr"> 833 </span>  screen-should-contain [
@@ -922,7 +922,7 @@ if ('onhashchange' in window) {
 <span id="L860" class="LineNr"> 860 </span>  <span class="Comment"># initialize editor with a wrapping line followed by a second line</span>
 <span id="L861" class="LineNr"> 861 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abcdef</span>
 <span id="L862" class="LineNr"> 862 </span><span class="Constant">g]</span>
-<span id="L863" class="LineNr"> 863 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L863" class="LineNr"> 863 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L864" class="LineNr"> 864 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L865" class="LineNr"> 865 </span>  $clear-trace
 <span id="L866" class="LineNr"> 866 </span>  screen-should-contain [
@@ -955,7 +955,7 @@ if ('onhashchange' in window) {
 <span id="L893" class="LineNr"> 893 </span>  <span class="Comment"># initialize editor with a line on the verge of wrapping, followed by a second line</span>
 <span id="L894" class="LineNr"> 894 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abcd</span>
 <span id="L895" class="LineNr"> 895 </span><span class="Constant">e]</span>
-<span id="L896" class="LineNr"> 896 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L896" class="LineNr"> 896 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L897" class="LineNr"> 897 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L898" class="LineNr"> 898 </span>  $clear-trace
 <span id="L899" class="LineNr"> 899 </span>  screen-should-contain [
@@ -991,7 +991,7 @@ if ('onhashchange' in window) {
 <span id="L929" class="LineNr"> 929 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L930" class="LineNr"> 930 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
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-<span id="L932" class="LineNr"> 932 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L932" class="LineNr"> 932 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L933" class="LineNr"> 933 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L934" class="LineNr"> 934 </span>  $clear-trace
 <span id="L935" class="LineNr"> 935 </span>  assume-console [
@@ -1105,7 +1105,7 @@ if ('onhashchange' in window) {
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 <span id="L1044" class="LineNr">1044 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[ab</span>
 <span id="L1045" class="LineNr">1045 </span><span class="Constant">def]</span>
-<span id="L1046" class="LineNr">1046 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1046" class="LineNr">1046 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1047" class="LineNr">1047 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1048" class="LineNr">1048 </span>  $clear-trace
 <span id="L1049" class="LineNr">1049 </span>  assume-console [
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 <span id="L1080" class="LineNr">1080 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
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 <span id="L1082" class="LineNr">1082 </span><span class="muRecipe">def</span>]
-<span id="L1083" class="LineNr">1083 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1083" class="LineNr">1083 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1084" class="LineNr">1084 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1085" class="LineNr">1085 </span>  $clear-trace
 <span id="L1086" class="LineNr">1086 </span>  assume-console [
@@ -1181,7 +1181,7 @@ if ('onhashchange' in window) {
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 <span id="L1120" class="LineNr">1120 </span><span class="Constant">def</span>
 <span id="L1121" class="LineNr">1121 </span><span class="Constant">ghi]</span>
-<span id="L1122" class="LineNr">1122 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1122" class="LineNr">1122 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1123" class="LineNr">1123 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1124" class="LineNr">1124 </span>  $clear-trace
 <span id="L1125" class="LineNr">1125 </span>  <span class="Comment"># click on the third line and hit up-arrow, so you end up just after a newline</span>
@@ -1221,7 +1221,7 @@ if ('onhashchange' in window) {
 <span id="L1159" class="LineNr">1159 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1160" class="LineNr">1160 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L1161" class="LineNr">1161 </span><span class="Constant">def]</span>
-<span id="L1162" class="LineNr">1162 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1162" class="LineNr">1162 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1163" class="LineNr">1163 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1164" class="LineNr">1164 </span>  $clear-trace
 <span id="L1165" class="LineNr">1165 </span>  <span class="Comment"># cursor starts out at (1, 0)</span>
@@ -1259,14 +1259,14 @@ if ('onhashchange' in window) {
 <span id="L1197" class="LineNr">1197 </span>  <span class="Conceal">¦</span> move-to-next-line?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65516/down-arrow</span>
 <span id="L1198" class="LineNr">1198 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> move-to-next-line?
 <span id="L1199" class="LineNr">1199 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-begin&gt;</span>
-<span id="L1200" class="LineNr">1200 </span>  <span class="Conceal">¦</span> go-render? <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L1207'>move-to-next-line</a> editor, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L1200" class="LineNr">1200 </span>  <span class="Conceal">¦</span> go-render? <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L1207'>move-to-next-line</a> editor, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L1201" class="LineNr">1201 </span>  <span class="Conceal">¦</span> undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">4/down-arrow</span>
 <span id="L1202" class="LineNr">1202 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-end&gt;</span>
 <span id="L1203" class="LineNr">1203 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
 <span id="L1204" class="LineNr">1204 </span>  <span class="Delimiter">}</span>
 <span id="L1205" class="LineNr">1205 </span>]
 <span id="L1206" class="LineNr">1206 </span>
-<span id="L1207" class="LineNr">1207 </span><span class="muRecipe">def</span> <a href='003-shortcuts.mu.html#L1207'>move-to-next-line</a> editor:&amp;:editor, <a href='../081print.mu.html#L587'>screen-height</a>:num<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
+<span id="L1207" class="LineNr">1207 </span><span class="muRecipe">def</span> <a href='003-shortcuts.mu.html#L1207'>move-to-next-line</a> editor:&amp;:editor, <a href='../081print.mu.html#L594'>screen-height</a>:num<span class="muRecipe"> -&gt; </span>go-render?:bool, editor:&amp;:editor [
 <span id="L1208" class="LineNr">1208 </span>  <span class="Constant">local-scope</span>
 <span id="L1209" class="LineNr">1209 </span>  <span class="Constant">load-ingredients</span>
 <span id="L1210" class="LineNr">1210 </span>  cursor-row:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">cursor-row:offset</span>
@@ -1274,7 +1274,7 @@ if ('onhashchange' in window) {
 <span id="L1212" class="LineNr">1212 </span>  before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
 <span id="L1213" class="LineNr">1213 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
 <span id="L1214" class="LineNr">1214 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
-<span id="L1215" class="LineNr">1215 </span>  last-line:num <span class="Special">&lt;-</span> subtract <a href='../081print.mu.html#L587'>screen-height</a>,<span class="Constant"> 1</span>
+<span id="L1215" class="LineNr">1215 </span>  last-line:num <span class="Special">&lt;-</span> subtract <a href='../081print.mu.html#L594'>screen-height</a>,<span class="Constant"> 1</span>
 <span id="L1216" class="LineNr">1216 </span>  already-at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal cursor-row, last-line
 <span id="L1217" class="LineNr">1217 </span>  <span class="Delimiter">{</span>
 <span id="L1218" class="LineNr">1218 </span>  <span class="Conceal">¦</span> <span class="Comment"># if cursor not at bottom, move it</span>
@@ -1325,7 +1325,7 @@ if ('onhashchange' in window) {
 <span id="L1263" class="LineNr">1263 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1264" class="LineNr">1264 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
 <span id="L1265" class="LineNr">1265 </span><span class="Constant">de]</span>
-<span id="L1266" class="LineNr">1266 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1266" class="LineNr">1266 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1267" class="LineNr">1267 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1268" class="LineNr">1268 </span>  $clear-trace
 <span id="L1269" class="LineNr">1269 </span>  assume-console [
@@ -1364,7 +1364,7 @@ if ('onhashchange' in window) {
 <span id="L1302" class="LineNr">1302 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1303" class="LineNr">1303 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1304" class="LineNr">1304 </span><span class="Constant">456]</span>
-<span id="L1305" class="LineNr">1305 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1305" class="LineNr">1305 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1306" class="LineNr">1306 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1307" class="LineNr">1307 </span>  $clear-trace
 <span id="L1308" class="LineNr">1308 </span>  <span class="Comment"># start on second line, press ctrl-a</span>
@@ -1438,7 +1438,7 @@ if ('onhashchange' in window) {
 <span id="L1376" class="LineNr">1376 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1377" class="LineNr">1377 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1378" class="LineNr">1378 </span><span class="Constant">456]</span>
-<span id="L1379" class="LineNr">1379 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1379" class="LineNr">1379 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1380" class="LineNr">1380 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1381" class="LineNr">1381 </span>  $clear-trace
 <span id="L1382" class="LineNr">1382 </span>  <span class="Comment"># start on first line (no newline before), press ctrl-a</span>
@@ -1464,7 +1464,7 @@ if ('onhashchange' in window) {
 <span id="L1402" class="LineNr">1402 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1403" class="LineNr">1403 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1404" class="LineNr">1404 </span><span class="Constant">456]</span>
-<span id="L1405" class="LineNr">1405 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1405" class="LineNr">1405 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1406" class="LineNr">1406 </span>  $clear-trace
 <span id="L1407" class="LineNr">1407 </span>  <span class="Comment"># start on second line, press 'home'</span>
 <span id="L1408" class="LineNr">1408 </span>  assume-console [
@@ -1489,7 +1489,7 @@ if ('onhashchange' in window) {
 <span id="L1427" class="LineNr">1427 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1428" class="LineNr">1428 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1429" class="LineNr">1429 </span><span class="Constant">456]</span>
-<span id="L1430" class="LineNr">1430 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1430" class="LineNr">1430 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1431" class="LineNr">1431 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1432" class="LineNr">1432 </span>  $clear-trace
 <span id="L1433" class="LineNr">1433 </span>  <span class="Comment"># start on first line (no newline before), press 'home'</span>
@@ -1517,7 +1517,7 @@ if ('onhashchange' in window) {
 <span id="L1455" class="LineNr">1455 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1456" class="LineNr">1456 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1457" class="LineNr">1457 </span><span class="Constant">456]</span>
-<span id="L1458" class="LineNr">1458 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1458" class="LineNr">1458 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1459" class="LineNr">1459 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1460" class="LineNr">1460 </span>  $clear-trace
 <span id="L1461" class="LineNr">1461 </span>  <span class="Comment"># start on first line, press ctrl-e</span>
@@ -1608,7 +1608,7 @@ if ('onhashchange' in window) {
 <span id="L1546" class="LineNr">1546 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1547" class="LineNr">1547 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1548" class="LineNr">1548 </span><span class="Constant">456]</span>
-<span id="L1549" class="LineNr">1549 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1549" class="LineNr">1549 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1550" class="LineNr">1550 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1551" class="LineNr">1551 </span>  $clear-trace
 <span id="L1552" class="LineNr">1552 </span>  <span class="Comment"># start on second line (no newline after), press ctrl-e</span>
@@ -1634,7 +1634,7 @@ if ('onhashchange' in window) {
 <span id="L1572" class="LineNr">1572 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1573" class="LineNr">1573 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1574" class="LineNr">1574 </span><span class="Constant">456]</span>
-<span id="L1575" class="LineNr">1575 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1575" class="LineNr">1575 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1576" class="LineNr">1576 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1577" class="LineNr">1577 </span>  $clear-trace
 <span id="L1578" class="LineNr">1578 </span>  <span class="Comment"># start on first line, press 'end'</span>
@@ -1660,7 +1660,7 @@ if ('onhashchange' in window) {
 <span id="L1598" class="LineNr">1598 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1599" class="LineNr">1599 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1600" class="LineNr">1600 </span><span class="Constant">456]</span>
-<span id="L1601" class="LineNr">1601 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1601" class="LineNr">1601 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1602" class="LineNr">1602 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1603" class="LineNr">1603 </span>  $clear-trace
 <span id="L1604" class="LineNr">1604 </span>  <span class="Comment"># start on second line (no newline after), press 'end'</span>
@@ -1688,7 +1688,7 @@ if ('onhashchange' in window) {
 <span id="L1626" class="LineNr">1626 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1627" class="LineNr">1627 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1628" class="LineNr">1628 </span><span class="Constant">456]</span>
-<span id="L1629" class="LineNr">1629 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1629" class="LineNr">1629 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1630" class="LineNr">1630 </span>  <span class="Comment"># start on second line, press ctrl-u</span>
 <span id="L1631" class="LineNr">1631 </span>  assume-console [
 <span id="L1632" class="LineNr">1632 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 2</span>
@@ -1751,7 +1751,7 @@ if ('onhashchange' in window) {
 <span id="L1689" class="LineNr">1689 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1690" class="LineNr">1690 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1691" class="LineNr">1691 </span><span class="Constant">456]</span>
-<span id="L1692" class="LineNr">1692 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1692" class="LineNr">1692 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1693" class="LineNr">1693 </span>  <span class="Comment"># start on first line (no newline before), press ctrl-u</span>
 <span id="L1694" class="LineNr">1694 </span>  assume-console [
 <span id="L1695" class="LineNr">1695 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 2</span>
@@ -1775,7 +1775,7 @@ if ('onhashchange' in window) {
 <span id="L1713" class="LineNr">1713 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1714" class="LineNr">1714 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1715" class="LineNr">1715 </span><span class="Constant">456]</span>
-<span id="L1716" class="LineNr">1716 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1716" class="LineNr">1716 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1717" class="LineNr">1717 </span>  <span class="Comment"># start past end of line, press ctrl-u</span>
 <span id="L1718" class="LineNr">1718 </span>  assume-console [
 <span id="L1719" class="LineNr">1719 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 3</span>
@@ -1799,7 +1799,7 @@ if ('onhashchange' in window) {
 <span id="L1737" class="LineNr">1737 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1738" class="LineNr">1738 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1739" class="LineNr">1739 </span><span class="Constant">456]</span>
-<span id="L1740" class="LineNr">1740 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1740" class="LineNr">1740 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1741" class="LineNr">1741 </span>  <span class="Comment"># start past end of final line, press ctrl-u</span>
 <span id="L1742" class="LineNr">1742 </span>  assume-console [
 <span id="L1743" class="LineNr">1743 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 3</span>
@@ -1825,7 +1825,7 @@ if ('onhashchange' in window) {
 <span id="L1763" class="LineNr">1763 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1764" class="LineNr">1764 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1765" class="LineNr">1765 </span><span class="Constant">456]</span>
-<span id="L1766" class="LineNr">1766 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1766" class="LineNr">1766 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L1768" class="LineNr">1768 </span>  assume-console [
 <span id="L1769" class="LineNr">1769 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 1</span>
@@ -1880,7 +1880,7 @@ if ('onhashchange' in window) {
 <span id="L1818" class="LineNr">1818 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1819" class="LineNr">1819 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1820" class="LineNr">1820 </span><span class="Constant">456]</span>
-<span id="L1821" class="LineNr">1821 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1821" class="LineNr">1821 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1822" class="LineNr">1822 </span>  <span class="Comment"># start on second line (no newline after), press ctrl-k</span>
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 <span id="L1824" class="LineNr">1824 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 1</span>
@@ -1904,7 +1904,7 @@ if ('onhashchange' in window) {
 <span id="L1842" class="LineNr">1842 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1843" class="LineNr">1843 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1844" class="LineNr">1844 </span><span class="Constant">456]</span>
-<span id="L1845" class="LineNr">1845 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1845" class="LineNr">1845 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L1848" class="LineNr">1848 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 2</span>
@@ -1928,7 +1928,7 @@ if ('onhashchange' in window) {
 <span id="L1866" class="LineNr">1866 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1867" class="LineNr">1867 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
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-<span id="L1869" class="LineNr">1869 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1869" class="LineNr">1869 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L1871" class="LineNr">1871 </span>  assume-console [
 <span id="L1872" class="LineNr">1872 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 3</span>
@@ -1952,7 +1952,7 @@ if ('onhashchange' in window) {
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 <span id="L1892" class="LineNr">1892 </span><span class="Constant">456]</span>
-<span id="L1893" class="LineNr">1893 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1893" class="LineNr">1893 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1894" class="LineNr">1894 </span>  <span class="Comment"># start at end of text</span>
 <span id="L1895" class="LineNr">1895 </span>  assume-console [
 <span id="L1896" class="LineNr">1896 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 2</span>
@@ -1976,7 +1976,7 @@ if ('onhashchange' in window) {
 <span id="L1914" class="LineNr">1914 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
 <span id="L1915" class="LineNr">1915 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[123</span>
 <span id="L1916" class="LineNr">1916 </span><span class="Constant">456]</span>
-<span id="L1917" class="LineNr">1917 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1917" class="LineNr">1917 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L1919" class="LineNr">1919 </span>  assume-console [
 <span id="L1920" class="LineNr">1920 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 3</span>
@@ -2006,7 +2006,7 @@ if ('onhashchange' in window) {
 <span id="L1944" class="LineNr">1944 </span><span class="Constant">b</span>
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-<span id="L1947" class="LineNr">1947 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L1947" class="LineNr">1947 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L1948" class="LineNr">1948 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L1949" class="LineNr">1949 </span>  screen-should-contain [
 <span id="L1950" class="LineNr">1950 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2085,7 +2085,7 @@ if ('onhashchange' in window) {
 <span id="L2023" class="LineNr">2023 </span><span class="Constant">g</span>
 <span id="L2024" class="LineNr">2024 </span><span class="Constant">h</span>
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-<span id="L2026" class="LineNr">2026 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2026" class="LineNr">2026 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2027" class="LineNr">2027 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2028" class="LineNr">2028 </span>  screen-should-contain [
 <span id="L2029" class="LineNr">2029 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2119,7 +2119,7 @@ if ('onhashchange' in window) {
 <span id="L2057" class="LineNr">2057 </span><span class="Constant">k</span>
 <span id="L2058" class="LineNr">2058 </span><span class="Constant">l</span>
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-<span id="L2060" class="LineNr">2060 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2060" class="LineNr">2060 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2061" class="LineNr">2061 </span>  <span class="Comment"># position cursor at last line, then try to move further down</span>
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@@ -2159,7 +2159,7 @@ if ('onhashchange' in window) {
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-<span id="L2100" class="LineNr">2100 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2100" class="LineNr">2100 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2101" class="LineNr">2101 </span>  <span class="Comment"># position cursor at end, type a character</span>
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 <span id="L2103" class="LineNr">2103 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 4</span>
@@ -2190,7 +2190,7 @@ if ('onhashchange' in window) {
 <span id="L2128" class="LineNr">2128 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[a</span>
 <span id="L2129" class="LineNr">2129 </span><span class="Constant">b</span>
 <span id="L2130" class="LineNr">2130 </span><span class="Constant">c]</span>
-<span id="L2131" class="LineNr">2131 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2131" class="LineNr">2131 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2132" class="LineNr">2132 </span>  assume-console [
 <span id="L2133" class="LineNr">2133 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 4</span>
 <span id="L2134" class="LineNr">2134 </span>  <span class="Conceal">¦</span> type [
@@ -2222,7 +2222,7 @@ if ('onhashchange' in window) {
 <span id="L2160" class="LineNr">2160 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[a</span>
 <span id="L2161" class="LineNr">2161 </span><span class="Constant">b</span>
 <span id="L2162" class="LineNr">2162 </span><span class="Constant">cdefgh]</span>
-<span id="L2163" class="LineNr">2163 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2163" class="LineNr">2163 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2164" class="LineNr">2164 </span>  <span class="Comment"># position cursor at end of screen and try to move right</span>
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@@ -2255,7 +2255,7 @@ if ('onhashchange' in window) {
 <span id="L2193" class="LineNr">2193 </span><span class="Constant">b</span>
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-<span id="L2196" class="LineNr">2196 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2196" class="LineNr">2196 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2197" class="LineNr">2197 </span>  <span class="Comment"># position cursor at end of screen and try to move right</span>
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 <span id="L2199" class="LineNr">2199 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 3</span>
@@ -2284,7 +2284,7 @@ if ('onhashchange' in window) {
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-<span id="L2225" class="LineNr">2225 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L2225" class="LineNr">2225 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L2227" class="LineNr">2227 </span>  $clear-trace
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@@ -2357,7 +2357,7 @@ if ('onhashchange' in window) {
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-<span id="L2298" class="LineNr">2298 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2298" class="LineNr">2298 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
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 <span id="L2300" class="LineNr">2300 </span>  <span class="Comment"># scroll down one page and one line</span>
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@@ -2388,7 +2388,7 @@ if ('onhashchange' in window) {
 <span id="L2326" class="LineNr">2326 </span><span class="Constant">b</span>
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-<span id="L2329" class="LineNr">2329 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L2329" class="LineNr">2329 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L2331" class="LineNr">2331 </span>  screen-should-contain [
 <span id="L2332" class="LineNr">2332 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2477,7 +2477,7 @@ if ('onhashchange' in window) {
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-<span id="L2418" class="LineNr">2418 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2418" class="LineNr">2418 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
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 <span id="L2420" class="LineNr">2420 </span>  screen-should-contain [
 <span id="L2421" class="LineNr">2421 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2523,7 +2523,7 @@ if ('onhashchange' in window) {
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-<span id="L2464" class="LineNr">2464 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2464" class="LineNr">2464 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2465" class="LineNr">2465 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
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@@ -2598,7 +2598,7 @@ if ('onhashchange' in window) {
 <span id="L2536" class="LineNr">2536 </span><span class="Constant">g</span>
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-<span id="L2539" class="LineNr">2539 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
+<span id="L2539" class="LineNr">2539 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
 <span id="L2540" class="LineNr">2540 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2541" class="LineNr">2541 </span>  screen-should-contain [
 <span id="L2542" class="LineNr">2542 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2646,7 +2646,7 @@ if ('onhashchange' in window) {
 <span id="L2584" class="LineNr">2584 </span>c
 <span id="L2585" class="LineNr">2585 </span>d
 <span id="L2586" class="LineNr">2586 </span>e]
-<span id="L2587" class="LineNr">2587 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
+<span id="L2587" class="LineNr">2587 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">6/right</span>
 <span id="L2588" class="LineNr">2588 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2589" class="LineNr">2589 </span>  assume-console [
 <span id="L2590" class="LineNr">2590 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
@@ -2696,7 +2696,7 @@ if ('onhashchange' in window) {
 <span id="L2634" class="LineNr">2634 </span><span class="Constant">c</span>
 <span id="L2635" class="LineNr">2635 </span><span class="Constant">d</span>
 <span id="L2636" class="LineNr">2636 </span><span class="Constant">e]</span>
-<span id="L2637" class="LineNr">2637 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
+<span id="L2637" class="LineNr">2637 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L2638" class="LineNr">2638 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2639" class="LineNr">2639 </span>  <span class="Comment"># position cursor at top of second page</span>
 <span id="L2640" class="LineNr">2640 </span>  assume-console [
@@ -2742,7 +2742,7 @@ if ('onhashchange' in window) {
 <span id="L2680" class="LineNr">2680 </span><span class="Constant">b</span>
 <span id="L2681" class="LineNr">2681 </span><span class="Constant">c</span>
 <span id="L2682" class="LineNr">2682 </span><span class="Constant">d]</span>
-<span id="L2683" class="LineNr">2683 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L2683" class="LineNr">2683 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L2684" class="LineNr">2684 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2685" class="LineNr">2685 </span>  screen-should-contain [
 <span id="L2686" class="LineNr">2686 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2792,7 +2792,7 @@ if ('onhashchange' in window) {
 <span id="L2730" class="LineNr">2730 </span><span class="Constant">b</span>
 <span id="L2731" class="LineNr">2731 </span><span class="Constant">c</span>
 <span id="L2732" class="LineNr">2732 </span><span class="Constant">d]</span>
-<span id="L2733" class="LineNr">2733 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L2733" class="LineNr">2733 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L2734" class="LineNr">2734 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2735" class="LineNr">2735 </span>  screen-should-contain [
 <span id="L2736" class="LineNr">2736 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2877,7 +2877,7 @@ if ('onhashchange' in window) {
 <span id="L2815" class="LineNr">2815 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">4/height</span>
 <span id="L2816" class="LineNr">2816 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[a</span>
 <span id="L2817" class="LineNr">2817 </span><span class="Constant">b]</span>
-<span id="L2818" class="LineNr">2818 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L2818" class="LineNr">2818 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L2819" class="LineNr">2819 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2820" class="LineNr">2820 </span>  screen-should-contain [
 <span id="L2821" class="LineNr">2821 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -2910,7 +2910,7 @@ if ('onhashchange' in window) {
 <span id="L2848" class="LineNr">2848 </span><span class="Constant">b</span>
 <span id="L2849" class="LineNr">2849 </span><span class="Constant">cdefgh]</span>
 <span id="L2850" class="LineNr">2850 </span>  <span class="Comment"># editor screen triggers wrap of last line</span>
-<span id="L2851" class="LineNr">2851 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+<span id="L2851" class="LineNr">2851 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
 <span id="L2852" class="LineNr">2852 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2853" class="LineNr">2853 </span>  <span class="Comment"># some part of last line is not displayed</span>
 <span id="L2854" class="LineNr">2854 </span>  screen-should-contain [
@@ -2943,7 +2943,7 @@ if ('onhashchange' in window) {
 <span id="L2881" class="LineNr">2881 </span>  <span class="Comment"># and still has something left over</span>
 <span id="L2882" class="LineNr">2882 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[a</span>
 <span id="L2883" class="LineNr">2883 </span><span class="Constant">bcdefgh]</span>
-<span id="L2884" class="LineNr">2884 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+<span id="L2884" class="LineNr">2884 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
 <span id="L2885" class="LineNr">2885 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2886" class="LineNr">2886 </span>  <span class="Comment"># some part of last line is not displayed</span>
 <span id="L2887" class="LineNr">2887 </span>  screen-should-contain [
@@ -2977,7 +2977,7 @@ if ('onhashchange' in window) {
 <span id="L2915" class="LineNr">2915 </span><span class="Constant">b</span>
 <span id="L2916" class="LineNr">2916 </span><span class="Constant">c</span>
 <span id="L2917" class="LineNr">2917 </span><span class="Constant">d]</span>
-<span id="L2918" class="LineNr">2918 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L2918" class="LineNr">2918 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L2919" class="LineNr">2919 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L2920" class="LineNr">2920 </span>  screen-should-contain [
 <span id="L2921" class="LineNr">2921 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -3021,7 +3021,7 @@ if ('onhashchange' in window) {
 <span id="L2959" class="LineNr">2959 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-up?
 <span id="L2960" class="LineNr">2960 </span>  <span class="Conceal">¦</span> old-top:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
 <span id="L2961" class="LineNr">2961 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-begin&gt;</span>
-<span id="L2962" class="LineNr">2962 </span>  <span class="Conceal">¦</span> editor <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L2987'>page-up</a> editor, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L2962" class="LineNr">2962 </span>  <span class="Conceal">¦</span> editor <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L2987'>page-up</a> editor, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L2963" class="LineNr">2963 </span>  <span class="Conceal">¦</span> undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span id="L2964" class="LineNr">2964 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-end&gt;</span>
 <span id="L2965" class="LineNr">2965 </span>  <span class="Conceal">¦</span> top-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
@@ -3036,7 +3036,7 @@ if ('onhashchange' in window) {
 <span id="L2974" class="LineNr">2974 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-up?
 <span id="L2975" class="LineNr">2975 </span>  <span class="Conceal">¦</span> old-top:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
 <span id="L2976" class="LineNr">2976 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-begin&gt;</span>
-<span id="L2977" class="LineNr">2977 </span>  <span class="Conceal">¦</span> editor <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L2987'>page-up</a> editor, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L2977" class="LineNr">2977 </span>  <span class="Conceal">¦</span> editor <span class="Special">&lt;-</span> <a href='003-shortcuts.mu.html#L2987'>page-up</a> editor, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L2978" class="LineNr">2978 </span>  <span class="Conceal">¦</span> undo-coalesce-tag:num <span class="Special">&lt;-</span> copy <span class="Constant">0/never</span>
 <span id="L2979" class="LineNr">2979 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;move-cursor-end&gt;</span>
 <span id="L2980" class="LineNr">2980 </span>  <span class="Conceal">¦</span> top-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
@@ -3046,10 +3046,10 @@ if ('onhashchange' in window) {
 <span id="L2984" class="LineNr">2984 </span>  <span class="Delimiter">}</span>
 <span id="L2985" class="LineNr">2985 </span>]
 <span id="L2986" class="LineNr">2986 </span>
-<span id="L2987" class="LineNr">2987 </span><span class="muRecipe">def</span> <a href='003-shortcuts.mu.html#L2987'>page-up</a> editor:&amp;:editor, <a href='../081print.mu.html#L587'>screen-height</a>:num<span class="muRecipe"> -&gt; </span>editor:&amp;:editor [
+<span id="L2987" class="LineNr">2987 </span><span class="muRecipe">def</span> <a href='003-shortcuts.mu.html#L2987'>page-up</a> editor:&amp;:editor, <a href='../081print.mu.html#L594'>screen-height</a>:num<span class="muRecipe"> -&gt; </span>editor:&amp;:editor [
 <span id="L2988" class="LineNr">2988 </span>  <span class="Constant">local-scope</span>
 <span id="L2989" class="LineNr">2989 </span>  <span class="Constant">load-ingredients</span>
-<span id="L2990" class="LineNr">2990 </span>  max:num <span class="Special">&lt;-</span> subtract <a href='../081print.mu.html#L587'>screen-height</a>, <span class="Constant">1/menu-bar</span>, <span class="Constant">1/overlapping-line</span>
+<span id="L2990" class="LineNr">2990 </span>  max:num <span class="Special">&lt;-</span> subtract <a href='../081print.mu.html#L594'>screen-height</a>, <span class="Constant">1/menu-bar</span>, <span class="Constant">1/overlapping-line</span>
 <span id="L2991" class="LineNr">2991 </span>  count:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
 <span id="L2992" class="LineNr">2992 </span>  top-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
 <span id="L2993" class="LineNr">2993 </span>  <span class="Delimiter">{</span>
@@ -3077,7 +3077,7 @@ if ('onhashchange' in window) {
 <span id="L3015" class="LineNr">3015 </span><span class="Constant">f</span>
 <span id="L3016" class="LineNr">3016 </span><span class="Constant">g</span>
 <span id="L3017" class="LineNr">3017 </span><span class="Constant">h]</span>
-<span id="L3018" class="LineNr">3018 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L3018" class="LineNr">3018 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L3019" class="LineNr">3019 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L3020" class="LineNr">3020 </span>  screen-should-contain [
 <span id="L3021" class="LineNr">3021 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -3146,7 +3146,7 @@ if ('onhashchange' in window) {
 <span id="L3084" class="LineNr">3084 </span><span class="Constant">n</span>
 <span id="L3085" class="LineNr">3085 </span><span class="Constant">o]</span>
 <span id="L3086" class="LineNr">3086 </span>  <span class="Comment"># editor screen triggers wrap of last line</span>
-<span id="L3087" class="LineNr">3087 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+<span id="L3087" class="LineNr">3087 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
 <span id="L3088" class="LineNr">3088 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L3089" class="LineNr">3089 </span>  <span class="Comment"># some part of last line is not displayed</span>
 <span id="L3090" class="LineNr">3090 </span>  screen-should-contain [
@@ -3201,7 +3201,7 @@ if ('onhashchange' in window) {
 <span id="L3139" class="LineNr">3139 </span>  <span class="Comment"># and still has something left over</span>
 <span id="L3140" class="LineNr">3140 </span>  s:text <span class="Special">&lt;-</span> new <span class="Constant">[a</span>
 <span id="L3141" class="LineNr">3141 </span><span class="Constant">bcdefgh]</span>
-<span id="L3142" class="LineNr">3142 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+<span id="L3142" class="LineNr">3142 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
 <span id="L3143" class="LineNr">3143 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L3144" class="LineNr">3144 </span>  <span class="Comment"># some part of last line is not displayed</span>
 <span id="L3145" class="LineNr">3145 </span>  screen-should-contain [
@@ -3253,7 +3253,7 @@ if ('onhashchange' in window) {
 <span id="L3191" class="LineNr">3191 </span><span class="Constant">gxx</span>
 <span id="L3192" class="LineNr">3192 </span><span class="Constant">hxx</span>
 <span id="L3193" class="LineNr">3193 </span><span class="Constant">]</span>
-<span id="L3194" class="LineNr">3194 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+<span id="L3194" class="LineNr">3194 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
 <span id="L3195" class="LineNr">3195 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L3196" class="LineNr">3196 </span>  screen-should-contain [
 <span id="L3197" class="LineNr">3197 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
@@ -3313,7 +3313,7 @@ if ('onhashchange' in window) {
 <span id="L3251" class="LineNr">3251 </span>fxy
 <span id="L3252" class="LineNr">3252 </span>gxy
 <span id="L3253" class="LineNr">3253 </span>]
-<span id="L3254" class="LineNr">3254 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
+<span id="L3254" class="LineNr">3254 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> s, <span class="Constant">0/left</span>, <span class="Constant">4/right</span>
 <span id="L3255" class="LineNr">3255 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L3256" class="LineNr">3256 </span>  screen-should-contain [
 <span id="L3257" class="LineNr">3257 </span>  <span class="Conceal">¦</span><span class="Constant"> .          .</span>
diff --git a/html/edit/004-programming-environment.mu.html b/html/edit/004-programming-environment.mu.html
index bc4394cd..87f2586b 100644
--- a/html/edit/004-programming-environment.mu.html
+++ b/html/edit/004-programming-environment.mu.html
@@ -70,7 +70,7 @@ if ('onhashchange' in window) {
 <span id="L7" class="LineNr">  7 </span>  <span class="Constant">local-scope</span>
 <span id="L8" class="LineNr">  8 </span>  open-console
 <span id="L9" class="LineNr">  9 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <span class="Constant">0/filesystem</span>, <span class="Constant">0/screen</span>
-<span id="L10" class="LineNr"> 10 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <span class="Constant">0/screen</span>, env, <a href='001-editor.mu.html#L121'>render</a>
+<span id="L10" class="LineNr"> 10 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <span class="Constant">0/screen</span>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L11" class="LineNr"> 11 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, env, <span class="Constant">0/filesystem</span>
 <span id="L12" class="LineNr"> 12 </span>  <span class="Comment"># never gets here</span>
 <span id="L13" class="LineNr"> 13 </span>]
@@ -84,15 +84,15 @@ if ('onhashchange' in window) {
 <span id="L21" class="LineNr"> 21 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, test-sandbox-editor-contents:text<span class="muRecipe"> -&gt; </span>result:&amp;:environment [
 <span id="L22" class="LineNr"> 22 </span>  <span class="Constant">local-scope</span>
 <span id="L23" class="LineNr"> 23 </span>  <span class="Constant">load-ingredients</span>
-<span id="L24" class="LineNr"> 24 </span>  width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L24" class="LineNr"> 24 </span>  width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L25" class="LineNr"> 25 </span>  result <span class="Special">&lt;-</span> new <span class="Constant">environment:type</span>
 <span id="L26" class="LineNr"> 26 </span>  <span class="Comment"># recipe editor on the left</span>
 <span id="L27" class="LineNr"> 27 </span>  initial-recipe-contents:text <span class="Special">&lt;-</span> <a href='../088file.mu.html#L38'>slurp</a> <a href='../088file.mu.html#L11'>resources</a>, <span class="Constant">[lesson/recipes.mu]</span>  <span class="Comment"># ignore errors</span>
 <span id="L28" class="LineNr"> 28 </span>  divider:num, _ <span class="Special">&lt;-</span> divide-with-remainder width,<span class="Constant"> 2</span>
-<span id="L29" class="LineNr"> 29 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> initial-recipe-contents, <span class="Constant">0/left</span>, divider/right
+<span id="L29" class="LineNr"> 29 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> initial-recipe-contents, <span class="Constant">0/left</span>, divider/right
 <span id="L30" class="LineNr"> 30 </span>  <span class="Comment"># sandbox editor on the right</span>
 <span id="L31" class="LineNr"> 31 </span>  sandbox-left:num <span class="Special">&lt;-</span> add divider,<span class="Constant"> 1</span>
-<span id="L32" class="LineNr"> 32 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> test-sandbox-editor-contents, sandbox-left, width/right
+<span id="L32" class="LineNr"> 32 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> test-sandbox-editor-contents, sandbox-left, width/right
 <span id="L33" class="LineNr"> 33 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">recipes:offset</span>, recipes
 <span id="L34" class="LineNr"> 34 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">current-sandbox:offset</span>, current-sandbox
 <span id="L35" class="LineNr"> 35 </span>  *result <span class="Special">&lt;-</span> put *result, <span class="Constant">sandbox-in-focus?:offset</span>, <span class="Constant">0/false</span>
@@ -105,464 +105,490 @@ if ('onhashchange' in window) {
 <span id="L42" class="LineNr"> 42 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
 <span id="L43" class="LineNr"> 43 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
 <span id="L44" class="LineNr"> 44 </span>  sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
-<span id="L45" class="LineNr"> 45 </span>  <span class="Delimiter">{</span>
-<span id="L46" class="LineNr"> 46 </span>  <span class="Conceal">¦</span> <span class="Comment"># looping over each (keyboard or touch) event as it occurs</span>
-<span id="L47" class="LineNr"> 47 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-event</span>
-<span id="L48" class="LineNr"> 48 </span>  <span class="Conceal">¦</span> e:<a href='../084console.mu.html#L4'>event</a>, found?:bool, quit?:bool, <a href='../084console.mu.html#L23'>console</a> <span class="Special">&lt;-</span> <a href='../084console.mu.html#L35'>read-event</a> <a href='../084console.mu.html#L23'>console</a>
-<span id="L49" class="LineNr"> 49 </span>  <span class="Conceal">¦</span> <span class="muControl">loop-unless</span> found?
-<span id="L50" class="LineNr"> 50 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> quit?  <span class="Comment"># only in tests</span>
-<span id="L51" class="LineNr"> 51 </span>  <span class="Conceal">¦</span> trace<span class="Constant"> 10</span>, <span class="Constant">[app]</span>, <span class="Constant">[next-event]</span>
-<span id="L52" class="LineNr"> 52 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L52'>&lt;handle-event&gt;</a></span>
-<span id="L53" class="LineNr"> 53 </span>  <span class="Conceal">¦</span> <span class="Comment"># check for global events that will trigger regardless of which editor has focus</span>
-<span id="L54" class="LineNr"> 54 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L55" class="LineNr"> 55 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> k:num, is-keycode?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant">keycode:variant</span>
-<span id="L56" class="LineNr"> 56 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-keycode?
-<span id="L57" class="LineNr"> 57 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L57'>&lt;global-keypress&gt;</a></span>
-<span id="L58" class="LineNr"> 58 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L59" class="LineNr"> 59 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L60" class="LineNr"> 60 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> c:char, is-unicode?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant">text:variant</span>
-<span id="L61" class="LineNr"> 61 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-unicode?
-<span id="L62" class="LineNr"> 62 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L62'>&lt;global-type&gt;</a></span>
-<span id="L63" class="LineNr"> 63 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L64" class="LineNr"> 64 </span>  <span class="Conceal">¦</span> <span class="Comment"># 'touch' event - send to both sides, see what picks it up</span>
-<span id="L65" class="LineNr"> 65 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L66" class="LineNr"> 66 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> t:<a href='../084console.mu.html#L12'>touch-event</a>, is-touch?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant">touch:variant</span>
-<span id="L67" class="LineNr"> 67 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-touch?
-<span id="L68" class="LineNr"> 68 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># ignore all but 'left-click' events for now</span>
-<span id="L69" class="LineNr"> 69 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># todo: test this</span>
-<span id="L70" class="LineNr"> 70 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> touch-type:num <span class="Special">&lt;-</span> get t, <span class="Constant">type:offset</span>
-<span id="L71" class="LineNr"> 71 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> is-left-click?:bool <span class="Special">&lt;-</span> equal touch-type, <span class="Constant">65513/mouse-left</span>
-<span id="L72" class="LineNr"> 72 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop-unless</span> is-left-click?, <span class="Constant">+next-event</span>
-<span id="L73" class="LineNr"> 73 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> click-row:num <span class="Special">&lt;-</span> get t, <span class="Constant">row:offset</span>
-<span id="L74" class="LineNr"> 74 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> click-column:num <span class="Special">&lt;-</span> get t, <span class="Constant">column:offset</span>
-<span id="L75" class="LineNr"> 75 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># later exceptions for non-editor touches will go here</span>
-<span id="L76" class="LineNr"> 76 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L76'>&lt;global-touch&gt;</a></span>
-<span id="L77" class="LineNr"> 77 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># send to both editors</span>
-<span id="L78" class="LineNr"> 78 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> _ <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L48'>move-cursor-in-editor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, t
-<span id="L79" class="LineNr"> 79 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> sandbox-in-focus?:bool <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L48'>move-cursor-in-editor</a> <a href='../081print.mu.html#L4'>screen</a>, current-sandbox, t
-<span id="L80" class="LineNr"> 80 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, sandbox-in-focus?
-<span id="L81" class="LineNr"> 81 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L82" class="LineNr"> 82 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L83" class="LineNr"> 83 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L84" class="LineNr"> 84 </span>  <span class="Conceal">¦</span> <span class="Comment"># 'resize' event - redraw editor</span>
-<span id="L85" class="LineNr"> 85 </span>  <span class="Conceal">¦</span> <span class="Comment"># todo: test this after supporting resize in assume-console</span>
-<span id="L86" class="LineNr"> 86 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L87" class="LineNr"> 87 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> r:<a href='../084console.mu.html#L18'>resize-event</a>, is-resize?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant"><a href='004-programming-environment.mu.html#L114'>resize</a>:variant</span>
-<span id="L88" class="LineNr"> 88 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-resize?
-<span id="L89" class="LineNr"> 89 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> env, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L114'>resize</a> <a href='../081print.mu.html#L4'>screen</a>, env
-<span id="L90" class="LineNr"> 90 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='004-programming-environment.mu.html#L141'>render-without-moving-cursor</a>
-<span id="L91" class="LineNr"> 91 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L92" class="LineNr"> 92 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L93" class="LineNr"> 93 </span>  <span class="Conceal">¦</span> <span class="Comment"># if it's not global and not a touch event, send to appropriate editor</span>
-<span id="L94" class="LineNr"> 94 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L95" class="LineNr"> 95 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
-<span id="L96" class="LineNr"> 96 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L97" class="LineNr"> 97 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
-<span id="L98" class="LineNr"> 98 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> render?:bool <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L164'>handle-keyboard-event</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, e:<a href='../084console.mu.html#L4'>event</a>
-<span id="L99" class="LineNr"> 99 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> render?
-<span id="L100" class="LineNr">100 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L101" class="LineNr">101 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L102" class="LineNr">102 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L103" class="LineNr">103 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
-<span id="L104" class="LineNr">104 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> render?:bool <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L164'>handle-keyboard-event</a> <a href='../081print.mu.html#L4'>screen</a>, current-sandbox, e:<a href='../084console.mu.html#L4'>event</a>
-<span id="L105" class="LineNr">105 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> render?
-<span id="L106" class="LineNr">106 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L107" class="LineNr">107 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L108" class="LineNr">108 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L109" class="LineNr">109 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L111" class="LineNr">111 </span>  <span class="Delimiter">}</span>
-<span id="L112" class="LineNr">112 </span>]
-<span id="L113" class="LineNr">113 </span>
-<span id="L114" class="LineNr">114 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L114'>resize</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment<span class="muRecipe"> -&gt; </span>env:&amp;:environment, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L115" class="LineNr">115 </span>  <span class="Constant">local-scope</span>
-<span id="L116" class="LineNr">116 </span>  <span class="Constant">load-ingredients</span>
-<span id="L117" class="LineNr">117 </span>  <a href='../081print.mu.html#L27'>clear-screen</a> <a href='../081print.mu.html#L4'>screen</a>  <span class="Comment"># update screen dimensions</span>
-<span id="L118" class="LineNr">118 </span>  width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L119" class="LineNr">119 </span>  divider:num, _ <span class="Special">&lt;-</span> divide-with-remainder width,<span class="Constant"> 2</span>
-<span id="L120" class="LineNr">120 </span>  <span class="Comment"># update recipe editor</span>
-<span id="L121" class="LineNr">121 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L122" class="LineNr">122 </span>  right:num <span class="Special">&lt;-</span> subtract divider,<span class="Constant"> 1</span>
-<span id="L123" class="LineNr">123 </span>  *recipes <span class="Special">&lt;-</span> put *recipes, <span class="Constant">right:offset</span>, right
-<span id="L124" class="LineNr">124 </span>  <span class="Comment"># reset cursor (later we'll try to preserve its position)</span>
-<span id="L125" class="LineNr">125 </span>  *recipes <span class="Special">&lt;-</span> put *recipes, <span class="Constant">cursor-row:offset</span>,<span class="Constant"> 1</span>
-<span id="L126" class="LineNr">126 </span>  *recipes <span class="Special">&lt;-</span> put *recipes, <span class="Constant">cursor-column:offset</span>,<span class="Constant"> 0</span>
-<span id="L127" class="LineNr">127 </span>  <span class="Comment"># update sandbox editor</span>
-<span id="L128" class="LineNr">128 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L129" class="LineNr">129 </span>  left:num <span class="Special">&lt;-</span> add divider,<span class="Constant"> 1</span>
-<span id="L130" class="LineNr">130 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">left:offset</span>, left
-<span id="L131" class="LineNr">131 </span>  right:num <span class="Special">&lt;-</span> subtract width,<span class="Constant"> 1</span>
-<span id="L132" class="LineNr">132 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">right:offset</span>, right
-<span id="L133" class="LineNr">133 </span>  <span class="Comment"># reset cursor (later we'll try to preserve its position)</span>
-<span id="L134" class="LineNr">134 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">cursor-row:offset</span>,<span class="Constant"> 1</span>
-<span id="L135" class="LineNr">135 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">cursor-column:offset</span>, left
-<span id="L136" class="LineNr">136 </span>]
-<span id="L137" class="LineNr">137 </span>
-<span id="L138" class="LineNr">138 </span><span class="Comment"># Variant of 'render' that updates cursor-row and cursor-column based on</span>
-<span id="L139" class="LineNr">139 </span><span class="Comment"># before-cursor (rather than the other way around). If before-cursor moves</span>
-<span id="L140" class="LineNr">140 </span><span class="Comment"># off-screen, it resets cursor-row and cursor-column.</span>
-<span id="L141" class="LineNr">141 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L141'>render-without-moving-cursor</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor<span class="muRecipe"> -&gt; </span>last-row:num, last-column:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor [
-<span id="L142" class="LineNr">142 </span>  <span class="Constant">local-scope</span>
-<span id="L143" class="LineNr">143 </span>  <span class="Constant">load-ingredients</span>
-<span id="L144" class="LineNr">144 </span>  <span class="muControl">return-unless</span> editor, <span class="Constant">1/top</span>, <span class="Constant">0/left</span>
-<span id="L145" class="LineNr">145 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
-<span id="L146" class="LineNr">146 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L147" class="LineNr">147 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
-<span id="L148" class="LineNr">148 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
-<span id="L149" class="LineNr">149 </span>  <a href='../065duplex_list.mu.html#L36'>prev</a>:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
-<span id="L150" class="LineNr">150 </span>  curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L151" class="LineNr">151 </span>  color:num <span class="Special">&lt;-</span> copy <span class="Constant">7/white</span>
-<span id="L152" class="LineNr">152 </span>  row:num <span class="Special">&lt;-</span> copy <span class="Constant">1/top</span>
-<span id="L153" class="LineNr">153 </span>  column:num <span class="Special">&lt;-</span> copy left
-<span id="L154" class="LineNr">154 </span>  <span class="Comment"># save before-cursor</span>
-<span id="L155" class="LineNr">155 </span>  old-before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
-<span id="L156" class="LineNr">156 </span>  <span class="Comment"># initialze cursor-row/cursor-column/before-cursor to the top of the screen</span>
-<span id="L157" class="LineNr">157 </span>  <span class="Comment"># by default</span>
-<span id="L158" class="LineNr">158 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, row
-<span id="L159" class="LineNr">159 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, column
-<span id="L160" class="LineNr">160 </span>  top-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
-<span id="L161" class="LineNr">161 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, top-of-screen
-<span id="L162" class="LineNr">162 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L163" class="LineNr">163 </span>  <span class="Delimiter">{</span>
-<span id="L164" class="LineNr">164 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
-<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
-<span id="L166" class="LineNr">166 </span>  <span class="Conceal">¦</span> off-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
-<span id="L167" class="LineNr">167 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> off-screen?
-<span id="L168" class="LineNr">168 </span>  <span class="Conceal">¦</span> <span class="Comment"># if we find old-before-cursor still on the new resized screen, update</span>
-<span id="L169" class="LineNr">169 </span>  <span class="Conceal">¦</span> <span class="Comment"># editor.cursor-row and editor.cursor-column based on</span>
-<span id="L170" class="LineNr">170 </span>  <span class="Conceal">¦</span> <span class="Comment"># old-before-cursor</span>
-<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor?:bool <span class="Special">&lt;-</span> equal old-before-cursor, <a href='../065duplex_list.mu.html#L36'>prev</a>
-<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor?
-<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, row
-<span id="L175" class="LineNr">175 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, column
-<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, old-before-cursor
-<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
-<span id="L179" class="LineNr">179 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;character-c-received&gt;</span>
-<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># newline? move to left rather than 0</span>
-<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
-<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> newline?
-<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of line in this window</span>
-<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
-<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># skip to next line</span>
-<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
-<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
-<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># at right? wrap. even if there's only one more letter left; we need</span>
-<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># room for clicking on the cursor after it.</span>
-<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> equal column, right
-<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-right?
-<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print wrap icon</span>
-<span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> wrap-icon:char <span class="Special">&lt;-</span> copy <span class="Constant">8617/loop-back-to-left</span>
-<span id="L201" class="LineNr">201 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
-<span id="L202" class="LineNr">202 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L203" class="LineNr">203 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># don't increment curr</span>
-<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
-<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
-<span id="L209" class="LineNr">209 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L210" class="LineNr">210 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
-<span id="L211" class="LineNr">211 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
-<span id="L212" class="LineNr">212 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L213" class="LineNr">213 </span>  <span class="Delimiter">}</span>
-<span id="L214" class="LineNr">214 </span>  <span class="Comment"># save first character off-screen</span>
-<span id="L215" class="LineNr">215 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom-of-screen:offset</span>, curr
-<span id="L216" class="LineNr">216 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom:offset</span>, row
-<span id="L217" class="LineNr">217 </span>  <span class="muControl">return</span> row, column
-<span id="L218" class="LineNr">218 </span>]
-<span id="L219" class="LineNr">219 </span>
-<span id="L220" class="LineNr">220 </span><span class="muScenario">scenario</span> point-at-multiple-editors [
-<span id="L221" class="LineNr">221 </span>  <span class="Constant">local-scope</span>
-<span id="L222" class="LineNr">222 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L223" class="LineNr">223 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
-<span id="L224" class="LineNr">224 </span>  <span class="Comment"># initialize both halves of screen</span>
-<span id="L225" class="LineNr">225 </span>  assume-resources [
-<span id="L226" class="LineNr">226 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L227" class="LineNr">227 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |abc|</span>
-<span id="L228" class="LineNr">228 </span>  <span class="Conceal">¦</span> ]
-<span id="L229" class="LineNr">229 </span>  ]
-<span id="L230" class="LineNr">230 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[def]</span>  <span class="Comment"># contents of sandbox editor</span>
-<span id="L231" class="LineNr">231 </span>  <span class="Comment"># focus on both sides</span>
-<span id="L232" class="LineNr">232 </span>  assume-console [
-<span id="L233" class="LineNr">233 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 1</span>
-<span id="L234" class="LineNr">234 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 17</span>
-<span id="L235" class="LineNr">235 </span>  ]
-<span id="L236" class="LineNr">236 </span>  <span class="Comment"># check cursor column in each</span>
-<span id="L237" class="LineNr">237 </span>  run [
-<span id="L238" class="LineNr">238 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L239" class="LineNr">239 </span>  <span class="Conceal">¦</span> recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L240" class="LineNr">240 </span>  <span class="Conceal">¦</span> 5:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-column:offset</span>
-<span id="L241" class="LineNr">241 </span>  <span class="Conceal">¦</span> sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L242" class="LineNr">242 </span>  <span class="Conceal">¦</span> 7:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">cursor-column:offset</span>
-<span id="L243" class="LineNr">243 </span>  ]
-<span id="L244" class="LineNr">244 </span>  memory-should-contain [
-<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span><span class="Constant"> 5</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>
-<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span><span class="Constant"> 7</span> <span class="Special">&lt;-</span><span class="Constant"> 17</span>
-<span id="L247" class="LineNr">247 </span>  ]
-<span id="L248" class="LineNr">248 </span>]
-<span id="L249" class="LineNr">249 </span>
-<span id="L250" class="LineNr">250 </span><span class="muScenario">scenario</span> edit-multiple-editors [
-<span id="L251" class="LineNr">251 </span>  <span class="Constant">local-scope</span>
-<span id="L252" class="LineNr">252 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L253" class="LineNr">253 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
-<span id="L254" class="LineNr">254 </span>  <span class="Comment"># initialize both halves of screen</span>
-<span id="L255" class="LineNr">255 </span>  assume-resources [
-<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L257" class="LineNr">257 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |abc|</span>
-<span id="L258" class="LineNr">258 </span>  <span class="Conceal">¦</span> ]
-<span id="L259" class="LineNr">259 </span>  ]
-<span id="L260" class="LineNr">260 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[def]</span>  <span class="Comment"># contents of sandbox</span>
-<span id="L261" class="LineNr">261 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L262" class="LineNr">262 </span>  <span class="Comment"># type one letter in each of them</span>
-<span id="L263" class="LineNr">263 </span>  assume-console [
-<span id="L264" class="LineNr">264 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 1</span>
-<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span> type <span class="Constant">[0]</span>
-<span id="L266" class="LineNr">266 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 17</span>
-<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span> type <span class="Constant">[1]</span>
-<span id="L268" class="LineNr">268 </span>  ]
-<span id="L269" class="LineNr">269 </span>  run [
-<span id="L270" class="LineNr">270 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span> recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L272" class="LineNr">272 </span>  <span class="Conceal">¦</span> 5:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-column:offset</span>
-<span id="L273" class="LineNr">273 </span>  <span class="Conceal">¦</span> sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L274" class="LineNr">274 </span>  <span class="Conceal">¦</span> 7:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">cursor-column:offset</span>
-<span id="L275" class="LineNr">275 </span>  ]
-<span id="L276" class="LineNr">276 </span>  screen-should-contain [
-<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .  # this line has a different background, but we don't test that yet</span>
-<span id="L278" class="LineNr">278 </span>  <span class="Conceal">¦</span><span class="Constant"> .a0bc           ╎d1ef          .</span>
-<span id="L279" class="LineNr">279 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
-<span id="L280" class="LineNr">280 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
-<span id="L281" class="LineNr">281 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
-<span id="L282" class="LineNr">282 </span>  ]
-<span id="L283" class="LineNr">283 </span>  memory-should-contain [
-<span id="L284" class="LineNr">284 </span>  <span class="Conceal">¦</span><span class="Constant"> 5</span> <span class="Special">&lt;-</span><span class="Constant"> 2</span>  <span class="Comment"># cursor column of recipe editor</span>
-<span id="L285" class="LineNr">285 </span>  <span class="Conceal">¦</span><span class="Constant"> 7</span> <span class="Special">&lt;-</span><span class="Constant"> 18</span>  <span class="Comment"># cursor column of sandbox editor</span>
+<span id="L45" class="LineNr"> 45 </span>  <span class="Comment"># if we fall behind we'll stop updating the screen, but then we have to</span>
+<span id="L46" class="LineNr"> 46 </span>  <span class="Comment"># render the entire screen when we catch up.</span>
+<span id="L47" class="LineNr"> 47 </span>  <span class="Comment"># todo: test this</span>
+<span id="L48" class="LineNr"> 48 </span>  render-all-on-no-more-events?:bool <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
+<span id="L49" class="LineNr"> 49 </span>  <span class="Delimiter">{</span>
+<span id="L50" class="LineNr"> 50 </span>  <span class="Conceal">¦</span> <span class="Comment"># looping over each (keyboard or touch) event as it occurs</span>
+<span id="L51" class="LineNr"> 51 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-event</span>
+<span id="L52" class="LineNr"> 52 </span>  <span class="Conceal">¦</span> e:<a href='../084console.mu.html#L4'>event</a>, found?:bool, quit?:bool, <a href='../084console.mu.html#L23'>console</a> <span class="Special">&lt;-</span> <a href='../084console.mu.html#L35'>read-event</a> <a href='../084console.mu.html#L23'>console</a>
+<span id="L53" class="LineNr"> 53 </span>  <span class="Conceal">¦</span> <span class="muControl">loop-unless</span> found?
+<span id="L54" class="LineNr"> 54 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> quit?  <span class="Comment"># only in tests</span>
+<span id="L55" class="LineNr"> 55 </span>  <span class="Conceal">¦</span> trace<span class="Constant"> 10</span>, <span class="Constant">[app]</span>, <span class="Constant">[next-event]</span>
+<span id="L56" class="LineNr"> 56 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L56'>&lt;handle-event&gt;</a></span>
+<span id="L57" class="LineNr"> 57 </span>  <span class="Conceal">¦</span> <span class="Comment"># check for global events that will trigger regardless of which editor has focus</span>
+<span id="L58" class="LineNr"> 58 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L59" class="LineNr"> 59 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> k:num, is-keycode?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant">keycode:variant</span>
+<span id="L60" class="LineNr"> 60 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-keycode?
+<span id="L61" class="LineNr"> 61 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span>
+<span id="L62" class="LineNr"> 62 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L63" class="LineNr"> 63 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L64" class="LineNr"> 64 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> c:char, is-unicode?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant">text:variant</span>
+<span id="L65" class="LineNr"> 65 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-unicode?
+<span id="L66" class="LineNr"> 66 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L66'>&lt;global-type&gt;</a></span>
+<span id="L67" class="LineNr"> 67 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L68" class="LineNr"> 68 </span>  <span class="Conceal">¦</span> <span class="Comment"># 'touch' event - send to both sides, see what picks it up</span>
+<span id="L69" class="LineNr"> 69 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L70" class="LineNr"> 70 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> t:<a href='../084console.mu.html#L12'>touch-event</a>, is-touch?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant">touch:variant</span>
+<span id="L71" class="LineNr"> 71 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-touch?
+<span id="L72" class="LineNr"> 72 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># ignore all but 'left-click' events for now</span>
+<span id="L73" class="LineNr"> 73 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># todo: test this</span>
+<span id="L74" class="LineNr"> 74 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> touch-type:num <span class="Special">&lt;-</span> get t, <span class="Constant">type:offset</span>
+<span id="L75" class="LineNr"> 75 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> is-left-click?:bool <span class="Special">&lt;-</span> equal touch-type, <span class="Constant">65513/mouse-left</span>
+<span id="L76" class="LineNr"> 76 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop-unless</span> is-left-click?, <span class="Constant">+next-event</span>
+<span id="L77" class="LineNr"> 77 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> click-row:num <span class="Special">&lt;-</span> get t, <span class="Constant">row:offset</span>
+<span id="L78" class="LineNr"> 78 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> click-column:num <span class="Special">&lt;-</span> get t, <span class="Constant">column:offset</span>
+<span id="L79" class="LineNr"> 79 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># later exceptions for non-editor touches will go here</span>
+<span id="L80" class="LineNr"> 80 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='004-programming-environment.mu.html#L80'>&lt;global-touch&gt;</a></span>
+<span id="L81" class="LineNr"> 81 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># send to both editors</span>
+<span id="L82" class="LineNr"> 82 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> _ <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L48'>move-cursor-in-editor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, t
+<span id="L83" class="LineNr"> 83 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> sandbox-in-focus?:bool <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L48'>move-cursor-in-editor</a> <a href='../081print.mu.html#L4'>screen</a>, current-sandbox, t
+<span id="L84" class="LineNr"> 84 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, sandbox-in-focus?
+<span id="L85" class="LineNr"> 85 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L86" class="LineNr"> 86 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L87" class="LineNr"> 87 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L88" class="LineNr"> 88 </span>  <span class="Conceal">¦</span> <span class="Comment"># 'resize' event - redraw editor</span>
+<span id="L89" class="LineNr"> 89 </span>  <span class="Conceal">¦</span> <span class="Comment"># todo: test this after supporting resize in assume-console</span>
+<span id="L90" class="LineNr"> 90 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L91" class="LineNr"> 91 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> r:<a href='../084console.mu.html#L18'>resize-event</a>, is-resize?:bool <span class="Special">&lt;-</span> maybe-convert e:<a href='../084console.mu.html#L4'>event</a>, <span class="Constant"><a href='004-programming-environment.mu.html#L125'>resize</a>:variant</span>
+<span id="L92" class="LineNr"> 92 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> is-resize?
+<span id="L93" class="LineNr"> 93 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> env, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L125'>resize</a> <a href='../081print.mu.html#L4'>screen</a>, env
+<span id="L94" class="LineNr"> 94 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='004-programming-environment.mu.html#L152'>render-without-moving-cursor</a>
+<span id="L95" class="LineNr"> 95 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L96" class="LineNr"> 96 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L97" class="LineNr"> 97 </span>  <span class="Conceal">¦</span> <span class="Comment"># if it's not global and not a touch event, send to appropriate editor</span>
+<span id="L98" class="LineNr"> 98 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L99" class="LineNr"> 99 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L100" class="LineNr">100 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
+<span id="L101" class="LineNr">101 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L102" class="LineNr">102 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
+<span id="L103" class="LineNr">103 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> render?:bool <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L164'>handle-keyboard-event</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, e:<a href='../084console.mu.html#L4'>event</a>
+<span id="L104" class="LineNr">104 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L105" class="LineNr">105 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L106" class="LineNr">106 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
+<span id="L107" class="LineNr">107 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> render?:bool <span class="Special">&lt;-</span> <a href='002-typing.mu.html#L164'>handle-keyboard-event</a> <a href='../081print.mu.html#L4'>screen</a>, current-sandbox, e:<a href='../084console.mu.html#L4'>event</a>
+<span id="L108" class="LineNr">108 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L109" class="LineNr">109 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># try to batch up rendering if there are more events queued up</span>
+<span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># to compensate for this additional code complexity, we always render both sides when we do render</span>
+<span id="L111" class="LineNr">111 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> render-all-on-no-more-events? <span class="Special">&lt;-</span> or render-all-on-no-more-events?, render?
+<span id="L112" class="LineNr">112 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> more-events?:bool <span class="Special">&lt;-</span> <a href='../084console.mu.html#L99'>has-more-events?</a> <a href='../084console.mu.html#L23'>console</a>
+<span id="L113" class="LineNr">113 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L114" class="LineNr">114 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> more-events?
+<span id="L115" class="LineNr">115 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> render-all-on-no-more-events?
+<span id="L116" class="LineNr">116 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L117" class="LineNr">117 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L118" class="LineNr">118 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L119" class="LineNr">119 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L120" class="LineNr">120 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L121" class="LineNr">121 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L122" class="LineNr">122 </span>  <span class="Delimiter">}</span>
+<span id="L123" class="LineNr">123 </span>]
+<span id="L124" class="LineNr">124 </span>
+<span id="L125" class="LineNr">125 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L125'>resize</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment<span class="muRecipe"> -&gt; </span>env:&amp;:environment, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L126" class="LineNr">126 </span>  <span class="Constant">local-scope</span>
+<span id="L127" class="LineNr">127 </span>  <span class="Constant">load-ingredients</span>
+<span id="L128" class="LineNr">128 </span>  <a href='../081print.mu.html#L27'>clear-screen</a> <a href='../081print.mu.html#L4'>screen</a>  <span class="Comment"># update screen dimensions</span>
+<span id="L129" class="LineNr">129 </span>  width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L130" class="LineNr">130 </span>  divider:num, _ <span class="Special">&lt;-</span> divide-with-remainder width,<span class="Constant"> 2</span>
+<span id="L131" class="LineNr">131 </span>  <span class="Comment"># update recipe editor</span>
+<span id="L132" class="LineNr">132 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
+<span id="L133" class="LineNr">133 </span>  right:num <span class="Special">&lt;-</span> subtract divider,<span class="Constant"> 1</span>
+<span id="L134" class="LineNr">134 </span>  *recipes <span class="Special">&lt;-</span> put *recipes, <span class="Constant">right:offset</span>, right
+<span id="L135" class="LineNr">135 </span>  <span class="Comment"># reset cursor (later we'll try to preserve its position)</span>
+<span id="L136" class="LineNr">136 </span>  *recipes <span class="Special">&lt;-</span> put *recipes, <span class="Constant">cursor-row:offset</span>,<span class="Constant"> 1</span>
+<span id="L137" class="LineNr">137 </span>  *recipes <span class="Special">&lt;-</span> put *recipes, <span class="Constant">cursor-column:offset</span>,<span class="Constant"> 0</span>
+<span id="L138" class="LineNr">138 </span>  <span class="Comment"># update sandbox editor</span>
+<span id="L139" class="LineNr">139 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L140" class="LineNr">140 </span>  left:num <span class="Special">&lt;-</span> add divider,<span class="Constant"> 1</span>
+<span id="L141" class="LineNr">141 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">left:offset</span>, left
+<span id="L142" class="LineNr">142 </span>  right:num <span class="Special">&lt;-</span> subtract width,<span class="Constant"> 1</span>
+<span id="L143" class="LineNr">143 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">right:offset</span>, right
+<span id="L144" class="LineNr">144 </span>  <span class="Comment"># reset cursor (later we'll try to preserve its position)</span>
+<span id="L145" class="LineNr">145 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">cursor-row:offset</span>,<span class="Constant"> 1</span>
+<span id="L146" class="LineNr">146 </span>  *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">cursor-column:offset</span>, left
+<span id="L147" class="LineNr">147 </span>]
+<span id="L148" class="LineNr">148 </span>
+<span id="L149" class="LineNr">149 </span><span class="Comment"># Variant of 'render' that updates cursor-row and cursor-column based on</span>
+<span id="L150" class="LineNr">150 </span><span class="Comment"># before-cursor (rather than the other way around). If before-cursor moves</span>
+<span id="L151" class="LineNr">151 </span><span class="Comment"># off-screen, it resets cursor-row and cursor-column.</span>
+<span id="L152" class="LineNr">152 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L152'>render-without-moving-cursor</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor<span class="muRecipe"> -&gt; </span>last-row:num, last-column:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, editor:&amp;:editor [
+<span id="L153" class="LineNr">153 </span>  <span class="Constant">local-scope</span>
+<span id="L154" class="LineNr">154 </span>  <span class="Constant">load-ingredients</span>
+<span id="L155" class="LineNr">155 </span>  <span class="muControl">return-unless</span> editor, <span class="Constant">1/top</span>, <span class="Constant">0/left</span>
+<span id="L156" class="LineNr">156 </span>  left:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">left:offset</span>
+<span id="L157" class="LineNr">157 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L158" class="LineNr">158 </span>  right:num <span class="Special">&lt;-</span> get *editor, <span class="Constant">right:offset</span>
+<span id="L159" class="LineNr">159 </span>  curr:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
+<span id="L160" class="LineNr">160 </span>  <a href='../065duplex_list.mu.html#L36'>prev</a>:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> copy curr  <span class="Comment"># just in case curr becomes null and we can't compute prev</span>
+<span id="L161" class="LineNr">161 </span>  curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L162" class="LineNr">162 </span>  color:num <span class="Special">&lt;-</span> copy <span class="Constant">7/white</span>
+<span id="L163" class="LineNr">163 </span>  row:num <span class="Special">&lt;-</span> copy <span class="Constant">1/top</span>
+<span id="L164" class="LineNr">164 </span>  column:num <span class="Special">&lt;-</span> copy left
+<span id="L165" class="LineNr">165 </span>  <span class="Comment"># save before-cursor</span>
+<span id="L166" class="LineNr">166 </span>  old-before-cursor:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">before-cursor:offset</span>
+<span id="L167" class="LineNr">167 </span>  <span class="Comment"># initialze cursor-row/cursor-column/before-cursor to the top of the screen</span>
+<span id="L168" class="LineNr">168 </span>  <span class="Comment"># by default</span>
+<span id="L169" class="LineNr">169 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, row
+<span id="L170" class="LineNr">170 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, column
+<span id="L171" class="LineNr">171 </span>  top-of-screen:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">top-of-screen:offset</span>
+<span id="L172" class="LineNr">172 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, top-of-screen
+<span id="L173" class="LineNr">173 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L174" class="LineNr">174 </span>  <span class="Delimiter">{</span>
+<span id="L175" class="LineNr">175 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
+<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
+<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span> off-screen?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> off-screen?
+<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span> <span class="Comment"># if we find old-before-cursor still on the new resized screen, update</span>
+<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> <span class="Comment"># editor.cursor-row and editor.cursor-column based on</span>
+<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> <span class="Comment"># old-before-cursor</span>
+<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-cursor?:bool <span class="Special">&lt;-</span> equal old-before-cursor, <a href='../065duplex_list.mu.html#L36'>prev</a>
+<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-cursor?
+<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-row:offset</span>, row
+<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">cursor-column:offset</span>, column
+<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">before-cursor:offset</span>, old-before-cursor
+<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
+<span id="L190" class="LineNr">190 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> &lt;character-c-received&gt;</span>
+<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># newline? move to left rather than 0</span>
+<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
+<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> newline?
+<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of line in this window</span>
+<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># skip to next line</span>
+<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
+<span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L201" class="LineNr">201 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L202" class="LineNr">202 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
+<span id="L203" class="LineNr">203 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
+<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># at right? wrap. even if there's only one more letter left; we need</span>
+<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># room for clicking on the cursor after it.</span>
+<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> equal column, right
+<span id="L209" class="LineNr">209 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-right?
+<span id="L210" class="LineNr">210 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print wrap icon</span>
+<span id="L211" class="LineNr">211 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> wrap-icon:char <span class="Special">&lt;-</span> copy <span class="Constant">8617/loop-back-to-left</span>
+<span id="L212" class="LineNr">212 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
+<span id="L213" class="LineNr">213 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
+<span id="L214" class="LineNr">214 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L215" class="LineNr">215 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L216" class="LineNr">216 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># don't increment curr</span>
+<span id="L217" class="LineNr">217 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
+<span id="L218" class="LineNr">218 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
+<span id="L220" class="LineNr">220 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L221" class="LineNr">221 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> <a href='../065duplex_list.mu.html#L36'>prev</a>
+<span id="L222" class="LineNr">222 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
+<span id="L223" class="LineNr">223 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L224" class="LineNr">224 </span>  <span class="Delimiter">}</span>
+<span id="L225" class="LineNr">225 </span>  <span class="Comment"># save first character off-screen</span>
+<span id="L226" class="LineNr">226 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom-of-screen:offset</span>, curr
+<span id="L227" class="LineNr">227 </span>  *editor <span class="Special">&lt;-</span> put *editor, <span class="Constant">bottom:offset</span>, row
+<span id="L228" class="LineNr">228 </span>  <span class="muControl">return</span> row, column
+<span id="L229" class="LineNr">229 </span>]
+<span id="L230" class="LineNr">230 </span>
+<span id="L231" class="LineNr">231 </span><span class="muScenario">scenario</span> point-at-multiple-editors [
+<span id="L232" class="LineNr">232 </span>  <span class="Constant">local-scope</span>
+<span id="L233" class="LineNr">233 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L234" class="LineNr">234 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
+<span id="L235" class="LineNr">235 </span>  <span class="Comment"># initialize both halves of screen</span>
+<span id="L236" class="LineNr">236 </span>  assume-resources [
+<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L238" class="LineNr">238 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |abc|</span>
+<span id="L239" class="LineNr">239 </span>  <span class="Conceal">¦</span> ]
+<span id="L240" class="LineNr">240 </span>  ]
+<span id="L241" class="LineNr">241 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[def]</span>  <span class="Comment"># contents of sandbox editor</span>
+<span id="L242" class="LineNr">242 </span>  <span class="Comment"># focus on both sides</span>
+<span id="L243" class="LineNr">243 </span>  assume-console [
+<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 1</span>
+<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 17</span>
+<span id="L246" class="LineNr">246 </span>  ]
+<span id="L247" class="LineNr">247 </span>  <span class="Comment"># check cursor column in each</span>
+<span id="L248" class="LineNr">248 </span>  run [
+<span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L250" class="LineNr">250 </span>  <span class="Conceal">¦</span> recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
+<span id="L251" class="LineNr">251 </span>  <span class="Conceal">¦</span> 5:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-column:offset</span>
+<span id="L252" class="LineNr">252 </span>  <span class="Conceal">¦</span> sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L253" class="LineNr">253 </span>  <span class="Conceal">¦</span> 7:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">cursor-column:offset</span>
+<span id="L254" class="LineNr">254 </span>  ]
+<span id="L255" class="LineNr">255 </span>  memory-should-contain [
+<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span><span class="Constant"> 5</span> <span class="Special">&lt;-</span><span class="Constant"> 1</span>
+<span id="L257" class="LineNr">257 </span>  <span class="Conceal">¦</span><span class="Constant"> 7</span> <span class="Special">&lt;-</span><span class="Constant"> 17</span>
+<span id="L258" class="LineNr">258 </span>  ]
+<span id="L259" class="LineNr">259 </span>]
+<span id="L260" class="LineNr">260 </span>
+<span id="L261" class="LineNr">261 </span><span class="muScenario">scenario</span> edit-multiple-editors [
+<span id="L262" class="LineNr">262 </span>  <span class="Constant">local-scope</span>
+<span id="L263" class="LineNr">263 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L264" class="LineNr">264 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
+<span id="L265" class="LineNr">265 </span>  <span class="Comment"># initialize both halves of screen</span>
+<span id="L266" class="LineNr">266 </span>  assume-resources [
+<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L268" class="LineNr">268 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |abc|</span>
+<span id="L269" class="LineNr">269 </span>  <span class="Conceal">¦</span> ]
+<span id="L270" class="LineNr">270 </span>  ]
+<span id="L271" class="LineNr">271 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[def]</span>  <span class="Comment"># contents of sandbox</span>
+<span id="L272" class="LineNr">272 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L273" class="LineNr">273 </span>  <span class="Comment"># type one letter in each of them</span>
+<span id="L274" class="LineNr">274 </span>  assume-console [
+<span id="L275" class="LineNr">275 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 1</span>
+<span id="L276" class="LineNr">276 </span>  <span class="Conceal">¦</span> type <span class="Constant">[0]</span>
+<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 17</span>
+<span id="L278" class="LineNr">278 </span>  <span class="Conceal">¦</span> type <span class="Constant">[1]</span>
+<span id="L279" class="LineNr">279 </span>  ]
+<span id="L280" class="LineNr">280 </span>  run [
+<span id="L281" class="LineNr">281 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L282" class="LineNr">282 </span>  <span class="Conceal">¦</span> recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
+<span id="L283" class="LineNr">283 </span>  <span class="Conceal">¦</span> 5:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-column:offset</span>
+<span id="L284" class="LineNr">284 </span>  <span class="Conceal">¦</span> sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L285" class="LineNr">285 </span>  <span class="Conceal">¦</span> 7:num/<span class="Special">raw</span> <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">cursor-column:offset</span>
 <span id="L286" class="LineNr">286 </span>  ]
-<span id="L287" class="LineNr">287 </span>  <span class="Comment"># show the cursor at the right window</span>
-<span id="L288" class="LineNr">288 </span>  run [
-<span id="L289" class="LineNr">289 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L290" class="LineNr">290 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L291" class="LineNr">291 </span>  ]
-<span id="L292" class="LineNr">292 </span>  screen-should-contain [
-<span id="L293" class="LineNr">293 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
-<span id="L294" class="LineNr">294 </span>  <span class="Conceal">¦</span><span class="Constant"> .a0bc           ╎d1␣f          .</span>
-<span id="L295" class="LineNr">295 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
-<span id="L296" class="LineNr">296 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
-<span id="L297" class="LineNr">297 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
-<span id="L298" class="LineNr">298 </span>  ]
-<span id="L299" class="LineNr">299 </span>]
-<span id="L300" class="LineNr">300 </span>
-<span id="L301" class="LineNr">301 </span><span class="muScenario">scenario</span> editor-in-focus-keeps-cursor [
-<span id="L302" class="LineNr">302 </span>  <span class="Constant">local-scope</span>
-<span id="L303" class="LineNr">303 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L304" class="LineNr">304 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
-<span id="L305" class="LineNr">305 </span>  assume-resources [
-<span id="L306" class="LineNr">306 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L307" class="LineNr">307 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |abc|</span>
-<span id="L308" class="LineNr">308 </span>  <span class="Conceal">¦</span> ]
+<span id="L287" class="LineNr">287 </span>  screen-should-contain [
+<span id="L288" class="LineNr">288 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .  # this line has a different background, but we don't test that yet</span>
+<span id="L289" class="LineNr">289 </span>  <span class="Conceal">¦</span><span class="Constant"> .a0bc           ╎d1ef          .</span>
+<span id="L290" class="LineNr">290 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
+<span id="L291" class="LineNr">291 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
+<span id="L292" class="LineNr">292 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
+<span id="L293" class="LineNr">293 </span>  ]
+<span id="L294" class="LineNr">294 </span>  memory-should-contain [
+<span id="L295" class="LineNr">295 </span>  <span class="Conceal">¦</span><span class="Constant"> 5</span> <span class="Special">&lt;-</span><span class="Constant"> 2</span>  <span class="Comment"># cursor column of recipe editor</span>
+<span id="L296" class="LineNr">296 </span>  <span class="Conceal">¦</span><span class="Constant"> 7</span> <span class="Special">&lt;-</span><span class="Constant"> 18</span>  <span class="Comment"># cursor column of sandbox editor</span>
+<span id="L297" class="LineNr">297 </span>  ]
+<span id="L298" class="LineNr">298 </span>  <span class="Comment"># show the cursor at the right window</span>
+<span id="L299" class="LineNr">299 </span>  run [
+<span id="L300" class="LineNr">300 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L301" class="LineNr">301 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L302" class="LineNr">302 </span>  ]
+<span id="L303" class="LineNr">303 </span>  screen-should-contain [
+<span id="L304" class="LineNr">304 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
+<span id="L305" class="LineNr">305 </span>  <span class="Conceal">¦</span><span class="Constant"> .a0bc           ╎d1␣f          .</span>
+<span id="L306" class="LineNr">306 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
+<span id="L307" class="LineNr">307 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
+<span id="L308" class="LineNr">308 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
 <span id="L309" class="LineNr">309 </span>  ]
-<span id="L310" class="LineNr">310 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[def]</span>
-<span id="L311" class="LineNr">311 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L312" class="LineNr">312 </span>  <span class="Comment"># initialize programming environment and highlight cursor</span>
-<span id="L313" class="LineNr">313 </span>  assume-console <span class="Constant">[]</span>
-<span id="L314" class="LineNr">314 </span>  run [
-<span id="L315" class="LineNr">315 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L318" class="LineNr">318 </span>  ]
-<span id="L319" class="LineNr">319 </span>  <span class="Comment"># is cursor at the right place?</span>
-<span id="L320" class="LineNr">320 </span>  screen-should-contain [
-<span id="L321" class="LineNr">321 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
-<span id="L322" class="LineNr">322 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣bc            ╎def           .</span>
-<span id="L323" class="LineNr">323 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
-<span id="L324" class="LineNr">324 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
-<span id="L325" class="LineNr">325 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
-<span id="L326" class="LineNr">326 </span>  ]
-<span id="L327" class="LineNr">327 </span>  <span class="Comment"># now try typing a letter</span>
-<span id="L328" class="LineNr">328 </span>  assume-console [
-<span id="L329" class="LineNr">329 </span>  <span class="Conceal">¦</span> type <span class="Constant">[z]</span>
-<span id="L330" class="LineNr">330 </span>  ]
-<span id="L331" class="LineNr">331 </span>  run [
-<span id="L332" class="LineNr">332 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L333" class="LineNr">333 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L334" class="LineNr">334 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L335" class="LineNr">335 </span>  ]
-<span id="L336" class="LineNr">336 </span>  <span class="Comment"># cursor should still be right</span>
-<span id="L337" class="LineNr">337 </span>  screen-should-contain [
-<span id="L338" class="LineNr">338 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
-<span id="L339" class="LineNr">339 </span>  <span class="Conceal">¦</span><span class="Constant"> .z␣bc           ╎def           .</span>
-<span id="L340" class="LineNr">340 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
-<span id="L341" class="LineNr">341 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
-<span id="L342" class="LineNr">342 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
-<span id="L343" class="LineNr">343 </span>  ]
-<span id="L344" class="LineNr">344 </span>]
-<span id="L345" class="LineNr">345 </span>
-<span id="L346" class="LineNr">346 </span><span class="muScenario">scenario</span> backspace-in-sandbox-editor-joins-lines [
-<span id="L347" class="LineNr">347 </span>  <span class="Constant">local-scope</span>
-<span id="L348" class="LineNr">348 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L349" class="LineNr">349 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
-<span id="L350" class="LineNr">350 </span>  assume-resources [
-<span id="L351" class="LineNr">351 </span>  ]
-<span id="L352" class="LineNr">352 </span>  <span class="Comment"># initialize sandbox side with two lines</span>
-<span id="L353" class="LineNr">353 </span>  test-sandbox-editor-contents:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
-<span id="L354" class="LineNr">354 </span><span class="Constant">def]</span>
-<span id="L355" class="LineNr">355 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, test-sandbox-editor-contents
-<span id="L356" class="LineNr">356 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L357" class="LineNr">357 </span>  screen-should-contain [
-<span id="L358" class="LineNr">358 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
-<span id="L359" class="LineNr">359 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎abc           .</span>
-<span id="L360" class="LineNr">360 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎def           .</span>
-<span id="L361" class="LineNr">361 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
-<span id="L362" class="LineNr">362 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
-<span id="L363" class="LineNr">363 </span>  ]
-<span id="L364" class="LineNr">364 </span>  <span class="Comment"># position cursor at start of second line and hit backspace</span>
-<span id="L365" class="LineNr">365 </span>  assume-console [
-<span id="L366" class="LineNr">366 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 16</span>
-<span id="L367" class="LineNr">367 </span>  <span class="Conceal">¦</span> press backspace
-<span id="L368" class="LineNr">368 </span>  ]
-<span id="L369" class="LineNr">369 </span>  run [
-<span id="L370" class="LineNr">370 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L371" class="LineNr">371 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L372" class="LineNr">372 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L373" class="LineNr">373 </span>  ]
-<span id="L374" class="LineNr">374 </span>  <span class="Comment"># cursor moves to end of old line</span>
-<span id="L375" class="LineNr">375 </span>  screen-should-contain [
-<span id="L376" class="LineNr">376 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
-<span id="L377" class="LineNr">377 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎abc␣ef        .</span>
-<span id="L378" class="LineNr">378 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎──────────────.</span>
-<span id="L379" class="LineNr">379 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
-<span id="L380" class="LineNr">380 </span>  ]
-<span id="L381" class="LineNr">381 </span>]
-<span id="L382" class="LineNr">382 </span>
-<span id="L383" class="LineNr">383 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
-<span id="L384" class="LineNr">384 </span>  <span class="Constant">local-scope</span>
-<span id="L385" class="LineNr">385 </span>  <span class="Constant">load-ingredients</span>
-<span id="L386" class="LineNr">386 </span>  trace<span class="Constant"> 10</span>, <span class="Constant">[app]</span>, <span class="Constant">[render all]</span>
-<span id="L387" class="LineNr">387 </span>  <span class="Comment"># top menu</span>
-<span id="L388" class="LineNr">388 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render top menu]</span>
-<span id="L389" class="LineNr">389 </span>  width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L390" class="LineNr">390 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>,<span class="Constant"> 0</span>, <span class="Constant">0/left</span>, width, <span class="Constant">32/space</span>, <span class="Constant">0/black</span>, <span class="Constant">238/grey</span>
-<span id="L391" class="LineNr">391 </span>  button-start:num <span class="Special">&lt;-</span> subtract width,<span class="Constant"> 20</span>
-<span id="L392" class="LineNr">392 </span>  button-on-screen?:bool <span class="Special">&lt;-</span> greater-or-equal button-start,<span class="Constant"> 0</span>
-<span id="L393" class="LineNr">393 </span>  assert button-on-screen?, <span class="Constant">[screen too narrow for menu]</span>
-<span id="L394" class="LineNr">394 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">0/row</span>, button-start
-<span id="L395" class="LineNr">395 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[ run (F4) ]</span>, <span class="Constant">255/white</span>, <span class="Constant">161/reddish</span>
-<span id="L396" class="LineNr">396 </span>  <span class="Comment"># dotted line down the middle</span>
-<span id="L397" class="LineNr">397 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render divider]</span>
-<span id="L398" class="LineNr">398 </span>  divider:num, _ <span class="Special">&lt;-</span> divide-with-remainder width,<span class="Constant"> 2</span>
-<span id="L399" class="LineNr">399 </span>  height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L400" class="LineNr">400 </span>  <a href='004-programming-environment.mu.html#L480'>draw-vertical</a> <a href='../081print.mu.html#L4'>screen</a>, divider, <span class="Constant">1/top</span>, height, <span class="Constant">9482/vertical-dotted</span>
-<span id="L401" class="LineNr">401 </span>  <span class="Comment">#</span>
-<span id="L402" class="LineNr">402 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L412'>render-recipes</a> <a href='../081print.mu.html#L4'>screen</a>, env, render-editor
-<span id="L403" class="LineNr">403 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, render-editor
-<span id="L404" class="LineNr">404 </span><span class="Constant">  <a href='004-programming-environment.mu.html#L404'>&lt;render-components-end&gt;</a></span>
-<span id="L405" class="LineNr">405 </span>  <span class="Comment">#</span>
-<span id="L406" class="LineNr">406 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L407" class="LineNr">407 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L408" class="LineNr">408 </span>  sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
-<span id="L409" class="LineNr">409 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L410" class="LineNr">410 </span>]
-<span id="L411" class="LineNr">411 </span>
-<span id="L412" class="LineNr">412 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L412'>render-recipes</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
-<span id="L413" class="LineNr">413 </span>  <span class="Constant">local-scope</span>
-<span id="L414" class="LineNr">414 </span>  <span class="Constant">load-ingredients</span>
-<span id="L415" class="LineNr">415 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render recipes]</span>
-<span id="L416" class="LineNr">416 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L417" class="LineNr">417 </span>  <span class="Comment"># render recipes</span>
-<span id="L418" class="LineNr">418 </span>  left:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">left:offset</span>
-<span id="L419" class="LineNr">419 </span>  right:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">right:offset</span>
-<span id="L420" class="LineNr">420 </span>  row:num, column:num, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> call render-editor, <a href='../081print.mu.html#L4'>screen</a>, recipes
-<span id="L421" class="LineNr">421 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
-<span id="L422" class="LineNr">422 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L423" class="LineNr">423 </span><span class="Constant">  <a href='004-programming-environment.mu.html#L423'>&lt;render-recipe-components-end&gt;</a></span>
-<span id="L424" class="LineNr">424 </span>  <span class="Comment"># draw dotted line after recipes</span>
-<span id="L425" class="LineNr">425 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right, <span class="Constant">9480/horizontal-dotted</span>
-<span id="L426" class="LineNr">426 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L427" class="LineNr">427 </span>  <a href='001-editor.mu.html#L221'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, left, right
-<span id="L428" class="LineNr">428 </span>]
-<span id="L429" class="LineNr">429 </span>
-<span id="L430" class="LineNr">430 </span><span class="Comment"># replaced in a later layer</span>
-<span id="L431" class="LineNr">431 </span><span class="muRecipe">def</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
-<span id="L432" class="LineNr">432 </span>  <span class="Constant">local-scope</span>
-<span id="L433" class="LineNr">433 </span>  <span class="Constant">load-ingredients</span>
-<span id="L434" class="LineNr">434 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L435" class="LineNr">435 </span>  left:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
-<span id="L436" class="LineNr">436 </span>  right:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">right:offset</span>
-<span id="L437" class="LineNr">437 </span>  row:num, column:num, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox <span class="Special">&lt;-</span> call render-editor, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox
-<span id="L438" class="LineNr">438 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
-<span id="L439" class="LineNr">439 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L440" class="LineNr">440 </span>  <span class="Comment"># draw solid line after code (you'll see why in later layers)</span>
-<span id="L441" class="LineNr">441 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
-<span id="L442" class="LineNr">442 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L443" class="LineNr">443 </span>  <a href='001-editor.mu.html#L221'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, left, right
-<span id="L444" class="LineNr">444 </span>]
-<span id="L445" class="LineNr">445 </span>
-<span id="L446" class="LineNr">446 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, recipes:&amp;:editor, current-sandbox:&amp;:editor, sandbox-in-focus?:bool, env:&amp;:environment<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L447" class="LineNr">447 </span>  <span class="Constant">local-scope</span>
-<span id="L448" class="LineNr">448 </span>  <span class="Constant">load-ingredients</span>
-<span id="L449" class="LineNr">449 </span><span class="Constant">  <a href='004-programming-environment.mu.html#L449'>&lt;update-cursor-special-cases&gt;</a></span>
-<span id="L450" class="LineNr">450 </span>  <span class="Delimiter">{</span>
-<span id="L451" class="LineNr">451 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
-<span id="L452" class="LineNr">452 </span>  <span class="Conceal">¦</span> cursor-row:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-row:offset</span>
-<span id="L453" class="LineNr">453 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-column:offset</span>
-<span id="L454" class="LineNr">454 </span>  <span class="Delimiter">}</span>
-<span id="L455" class="LineNr">455 </span>  <span class="Delimiter">{</span>
-<span id="L456" class="LineNr">456 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
-<span id="L457" class="LineNr">457 </span>  <span class="Conceal">¦</span> cursor-row:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">cursor-row:offset</span>
-<span id="L458" class="LineNr">458 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">cursor-column:offset</span>
-<span id="L459" class="LineNr">459 </span>  <span class="Delimiter">}</span>
-<span id="L460" class="LineNr">460 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
-<span id="L461" class="LineNr">461 </span>]
-<span id="L462" class="LineNr">462 </span>
-<span id="L463" class="LineNr">463 </span><span class="Comment"># ctrl-n - switch focus</span>
-<span id="L464" class="LineNr">464 </span><span class="Comment"># todo: test this</span>
-<span id="L465" class="LineNr">465 </span>
-<span id="L466" class="LineNr">466 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L62'>&lt;global-type&gt;</a></span> [
-<span id="L467" class="LineNr">467 </span>  <span class="Delimiter">{</span>
-<span id="L468" class="LineNr">468 </span>  <span class="Conceal">¦</span> switch-side?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">14/ctrl-n</span>
-<span id="L469" class="LineNr">469 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> switch-side?
-<span id="L470" class="LineNr">470 </span>  <span class="Conceal">¦</span> sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
-<span id="L471" class="LineNr">471 </span>  <span class="Conceal">¦</span> sandbox-in-focus? <span class="Special">&lt;-</span> not sandbox-in-focus?
-<span id="L472" class="LineNr">472 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, sandbox-in-focus?
-<span id="L473" class="LineNr">473 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L474" class="LineNr">474 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L475" class="LineNr">475 </span>  <span class="Delimiter">}</span>
-<span id="L476" class="LineNr">476 </span>]
-<span id="L477" class="LineNr">477 </span>
-<span id="L478" class="LineNr">478 </span><span class="SalientComment">## helpers</span>
-<span id="L479" class="LineNr">479 </span>
-<span id="L480" class="LineNr">480 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L480'>draw-vertical</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, col:num, y:num, bottom:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L481" class="LineNr">481 </span>  <span class="Constant">local-scope</span>
-<span id="L482" class="LineNr">482 </span>  <span class="Constant">load-ingredients</span>
-<span id="L483" class="LineNr">483 </span>  style:char, style-found?:bool <span class="Special">&lt;-</span> <span class="Constant">next-ingredient</span>
-<span id="L484" class="LineNr">484 </span>  <span class="Delimiter">{</span>
-<span id="L485" class="LineNr">485 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> style-found?
-<span id="L486" class="LineNr">486 </span>  <span class="Conceal">¦</span> style <span class="Special">&lt;-</span> copy <span class="Constant">9474/vertical</span>
-<span id="L487" class="LineNr">487 </span>  <span class="Delimiter">}</span>
-<span id="L488" class="LineNr">488 </span>  color:num, color-found?:bool <span class="Special">&lt;-</span> <span class="Constant">next-ingredient</span>
-<span id="L489" class="LineNr">489 </span>  <span class="Delimiter">{</span>
-<span id="L490" class="LineNr">490 </span>  <span class="Conceal">¦</span> <span class="Comment"># default color to white</span>
-<span id="L491" class="LineNr">491 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> color-found?
-<span id="L492" class="LineNr">492 </span>  <span class="Conceal">¦</span> color <span class="Special">&lt;-</span> copy <span class="Constant">245/grey</span>
-<span id="L493" class="LineNr">493 </span>  <span class="Delimiter">}</span>
-<span id="L494" class="LineNr">494 </span>  <span class="Delimiter">{</span>
-<span id="L495" class="LineNr">495 </span>  <span class="Conceal">¦</span> continue?:bool <span class="Special">&lt;-</span> lesser-than y, bottom
-<span id="L496" class="LineNr">496 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> continue?
-<span id="L497" class="LineNr">497 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, y, col
-<span id="L498" class="LineNr">498 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, style, color
-<span id="L499" class="LineNr">499 </span>  <span class="Conceal">¦</span> y <span class="Special">&lt;-</span> add y,<span class="Constant"> 1</span>
-<span id="L500" class="LineNr">500 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L310" class="LineNr">310 </span>]
+<span id="L311" class="LineNr">311 </span>
+<span id="L312" class="LineNr">312 </span><span class="muScenario">scenario</span> editor-in-focus-keeps-cursor [
+<span id="L313" class="LineNr">313 </span>  <span class="Constant">local-scope</span>
+<span id="L314" class="LineNr">314 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L315" class="LineNr">315 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
+<span id="L316" class="LineNr">316 </span>  assume-resources [
+<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L318" class="LineNr">318 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |abc|</span>
+<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span> ]
+<span id="L320" class="LineNr">320 </span>  ]
+<span id="L321" class="LineNr">321 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[def]</span>
+<span id="L322" class="LineNr">322 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L323" class="LineNr">323 </span>  <span class="Comment"># initialize programming environment and highlight cursor</span>
+<span id="L324" class="LineNr">324 </span>  assume-console <span class="Constant">[]</span>
+<span id="L325" class="LineNr">325 </span>  run [
+<span id="L326" class="LineNr">326 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L327" class="LineNr">327 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L328" class="LineNr">328 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L329" class="LineNr">329 </span>  ]
+<span id="L330" class="LineNr">330 </span>  <span class="Comment"># is cursor at the right place?</span>
+<span id="L331" class="LineNr">331 </span>  screen-should-contain [
+<span id="L332" class="LineNr">332 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
+<span id="L333" class="LineNr">333 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣bc            ╎def           .</span>
+<span id="L334" class="LineNr">334 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
+<span id="L335" class="LineNr">335 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
+<span id="L336" class="LineNr">336 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
+<span id="L337" class="LineNr">337 </span>  ]
+<span id="L338" class="LineNr">338 </span>  <span class="Comment"># now try typing a letter</span>
+<span id="L339" class="LineNr">339 </span>  assume-console [
+<span id="L340" class="LineNr">340 </span>  <span class="Conceal">¦</span> type <span class="Constant">[z]</span>
+<span id="L341" class="LineNr">341 </span>  ]
+<span id="L342" class="LineNr">342 </span>  run [
+<span id="L343" class="LineNr">343 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L344" class="LineNr">344 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L345" class="LineNr">345 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L346" class="LineNr">346 </span>  ]
+<span id="L347" class="LineNr">347 </span>  <span class="Comment"># cursor should still be right</span>
+<span id="L348" class="LineNr">348 </span>  screen-should-contain [
+<span id="L349" class="LineNr">349 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
+<span id="L350" class="LineNr">350 </span>  <span class="Conceal">¦</span><span class="Constant"> .z␣bc           ╎def           .</span>
+<span id="L351" class="LineNr">351 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
+<span id="L352" class="LineNr">352 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎              .</span>
+<span id="L353" class="LineNr">353 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
+<span id="L354" class="LineNr">354 </span>  ]
+<span id="L355" class="LineNr">355 </span>]
+<span id="L356" class="LineNr">356 </span>
+<span id="L357" class="LineNr">357 </span><span class="muScenario">scenario</span> backspace-in-sandbox-editor-joins-lines [
+<span id="L358" class="LineNr">358 </span>  <span class="Constant">local-scope</span>
+<span id="L359" class="LineNr">359 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L360" class="LineNr">360 </span>  assume-screen <span class="Constant">30/width</span>, <span class="Constant">5/height</span>
+<span id="L361" class="LineNr">361 </span>  assume-resources [
+<span id="L362" class="LineNr">362 </span>  ]
+<span id="L363" class="LineNr">363 </span>  <span class="Comment"># initialize sandbox side with two lines</span>
+<span id="L364" class="LineNr">364 </span>  test-sandbox-editor-contents:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
+<span id="L365" class="LineNr">365 </span><span class="Constant">def]</span>
+<span id="L366" class="LineNr">366 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, test-sandbox-editor-contents
+<span id="L367" class="LineNr">367 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L368" class="LineNr">368 </span>  screen-should-contain [
+<span id="L369" class="LineNr">369 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
+<span id="L370" class="LineNr">370 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎abc           .</span>
+<span id="L371" class="LineNr">371 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎def           .</span>
+<span id="L372" class="LineNr">372 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎──────────────.</span>
+<span id="L373" class="LineNr">373 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
+<span id="L374" class="LineNr">374 </span>  ]
+<span id="L375" class="LineNr">375 </span>  <span class="Comment"># position cursor at start of second line and hit backspace</span>
+<span id="L376" class="LineNr">376 </span>  assume-console [
+<span id="L377" class="LineNr">377 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 16</span>
+<span id="L378" class="LineNr">378 </span>  <span class="Conceal">¦</span> press backspace
+<span id="L379" class="LineNr">379 </span>  ]
+<span id="L380" class="LineNr">380 </span>  run [
+<span id="L381" class="LineNr">381 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L382" class="LineNr">382 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L383" class="LineNr">383 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L384" class="LineNr">384 </span>  ]
+<span id="L385" class="LineNr">385 </span>  <span class="Comment"># cursor moves to end of old line</span>
+<span id="L386" class="LineNr">386 </span>  screen-should-contain [
+<span id="L387" class="LineNr">387 </span>  <span class="Conceal">¦</span><span class="Constant"> .           run (F4)           .</span>
+<span id="L388" class="LineNr">388 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎abc␣ef        .</span>
+<span id="L389" class="LineNr">389 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎──────────────.</span>
+<span id="L390" class="LineNr">390 </span>  <span class="Conceal">¦</span><span class="Constant"> .               ╎              .</span>
+<span id="L391" class="LineNr">391 </span>  ]
+<span id="L392" class="LineNr">392 </span>]
+<span id="L393" class="LineNr">393 </span>
+<span id="L394" class="LineNr">394 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
+<span id="L395" class="LineNr">395 </span>  <span class="Constant">local-scope</span>
+<span id="L396" class="LineNr">396 </span>  <span class="Constant">load-ingredients</span>
+<span id="L397" class="LineNr">397 </span>  trace<span class="Constant"> 10</span>, <span class="Constant">[app]</span>, <span class="Constant">[render all]</span>
+<span id="L398" class="LineNr">398 </span>  <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L399" class="LineNr">399 </span>  <span class="Comment"># top menu</span>
+<span id="L400" class="LineNr">400 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render top menu]</span>
+<span id="L401" class="LineNr">401 </span>  width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L402" class="LineNr">402 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>,<span class="Constant"> 0</span>, <span class="Constant">0/left</span>, width, <span class="Constant">32/space</span>, <span class="Constant">0/black</span>, <span class="Constant">238/grey</span>
+<span id="L403" class="LineNr">403 </span>  button-start:num <span class="Special">&lt;-</span> subtract width,<span class="Constant"> 20</span>
+<span id="L404" class="LineNr">404 </span>  button-on-screen?:bool <span class="Special">&lt;-</span> greater-or-equal button-start,<span class="Constant"> 0</span>
+<span id="L405" class="LineNr">405 </span>  assert button-on-screen?, <span class="Constant">[screen too narrow for menu]</span>
+<span id="L406" class="LineNr">406 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">0/row</span>, button-start
+<span id="L407" class="LineNr">407 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[ run (F4) ]</span>, <span class="Constant">255/white</span>, <span class="Constant">161/reddish</span>
+<span id="L408" class="LineNr">408 </span>  <span class="Comment"># dotted line down the middle</span>
+<span id="L409" class="LineNr">409 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render divider]</span>
+<span id="L410" class="LineNr">410 </span>  divider:num, _ <span class="Special">&lt;-</span> divide-with-remainder width,<span class="Constant"> 2</span>
+<span id="L411" class="LineNr">411 </span>  height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L412" class="LineNr">412 </span>  <a href='004-programming-environment.mu.html#L506'>draw-vertical</a> <a href='../081print.mu.html#L4'>screen</a>, divider, <span class="Constant">1/top</span>, height, <span class="Constant">9482/vertical-dotted</span>
+<span id="L413" class="LineNr">413 </span>  <span class="Comment">#</span>
+<span id="L414" class="LineNr">414 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L426'>render-recipes</a> <a href='../081print.mu.html#L4'>screen</a>, env, render-editor
+<span id="L415" class="LineNr">415 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, render-editor
+<span id="L416" class="LineNr">416 </span><span class="Constant">  <a href='004-programming-environment.mu.html#L416'>&lt;render-components-end&gt;</a></span>
+<span id="L417" class="LineNr">417 </span>  <span class="Comment">#</span>
+<span id="L418" class="LineNr">418 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
+<span id="L419" class="LineNr">419 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L420" class="LineNr">420 </span>  sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
+<span id="L421" class="LineNr">421 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L422" class="LineNr">422 </span>  <span class="Comment">#</span>
+<span id="L423" class="LineNr">423 </span>  <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L424" class="LineNr">424 </span>]
+<span id="L425" class="LineNr">425 </span>
+<span id="L426" class="LineNr">426 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L426'>render-recipes</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
+<span id="L427" class="LineNr">427 </span>  <span class="Constant">local-scope</span>
+<span id="L428" class="LineNr">428 </span>  <span class="Constant">load-ingredients</span>
+<span id="L429" class="LineNr">429 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render recipes]</span>
+<span id="L430" class="LineNr">430 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
+<span id="L431" class="LineNr">431 </span>  <span class="Comment"># render recipes</span>
+<span id="L432" class="LineNr">432 </span>  left:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">left:offset</span>
+<span id="L433" class="LineNr">433 </span>  right:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">right:offset</span>
+<span id="L434" class="LineNr">434 </span>  row:num, column:num, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> call render-editor, <a href='../081print.mu.html#L4'>screen</a>, recipes
+<span id="L435" class="LineNr">435 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L436" class="LineNr">436 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L437" class="LineNr">437 </span><span class="Constant">  <a href='004-programming-environment.mu.html#L437'>&lt;render-recipe-components-end&gt;</a></span>
+<span id="L438" class="LineNr">438 </span>  <span class="Comment"># draw dotted line after recipes</span>
+<span id="L439" class="LineNr">439 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right, <span class="Constant">9480/horizontal-dotted</span>
+<span id="L440" class="LineNr">440 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L441" class="LineNr">441 </span>  <a href='001-editor.mu.html#L223'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, left, right
+<span id="L442" class="LineNr">442 </span>]
+<span id="L443" class="LineNr">443 </span>
+<span id="L444" class="LineNr">444 </span><span class="Comment"># replaced in a later layer</span>
+<span id="L445" class="LineNr">445 </span><span class="muRecipe">def</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
+<span id="L446" class="LineNr">446 </span>  <span class="Constant">local-scope</span>
+<span id="L447" class="LineNr">447 </span>  <span class="Constant">load-ingredients</span>
+<span id="L448" class="LineNr">448 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L449" class="LineNr">449 </span>  left:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
+<span id="L450" class="LineNr">450 </span>  right:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">right:offset</span>
+<span id="L451" class="LineNr">451 </span>  row:num, column:num, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox <span class="Special">&lt;-</span> call render-editor, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox
+<span id="L452" class="LineNr">452 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L453" class="LineNr">453 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L454" class="LineNr">454 </span>  <span class="Comment"># draw solid line after code (you'll see why in later layers)</span>
+<span id="L455" class="LineNr">455 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
+<span id="L456" class="LineNr">456 </span>  row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L457" class="LineNr">457 </span>  <a href='001-editor.mu.html#L223'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, left, right
+<span id="L458" class="LineNr">458 </span>]
+<span id="L459" class="LineNr">459 </span>
+<span id="L460" class="LineNr">460 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, recipes:&amp;:editor, current-sandbox:&amp;:editor, sandbox-in-focus?:bool, env:&amp;:environment<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L461" class="LineNr">461 </span>  <span class="Constant">local-scope</span>
+<span id="L462" class="LineNr">462 </span>  <span class="Constant">load-ingredients</span>
+<span id="L463" class="LineNr">463 </span><span class="Constant">  <a href='004-programming-environment.mu.html#L463'>&lt;update-cursor-special-cases&gt;</a></span>
+<span id="L464" class="LineNr">464 </span>  <span class="Delimiter">{</span>
+<span id="L465" class="LineNr">465 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
+<span id="L466" class="LineNr">466 </span>  <span class="Conceal">¦</span> cursor-row:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-row:offset</span>
+<span id="L467" class="LineNr">467 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *recipes, <span class="Constant">cursor-column:offset</span>
+<span id="L468" class="LineNr">468 </span>  <span class="Delimiter">}</span>
+<span id="L469" class="LineNr">469 </span>  <span class="Delimiter">{</span>
+<span id="L470" class="LineNr">470 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
+<span id="L471" class="LineNr">471 </span>  <span class="Conceal">¦</span> cursor-row:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">cursor-row:offset</span>
+<span id="L472" class="LineNr">472 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">cursor-column:offset</span>
+<span id="L473" class="LineNr">473 </span>  <span class="Delimiter">}</span>
+<span id="L474" class="LineNr">474 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, cursor-row, cursor-column
+<span id="L475" class="LineNr">475 </span>]
+<span id="L476" class="LineNr">476 </span>
+<span id="L477" class="LineNr">477 </span><span class="Comment"># ctrl-l - redraw screen (just in case it printed junk somehow)</span>
+<span id="L478" class="LineNr">478 </span>
+<span id="L479" class="LineNr">479 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L66'>&lt;global-type&gt;</a></span> [
+<span id="L480" class="LineNr">480 </span>  <span class="Delimiter">{</span>
+<span id="L481" class="LineNr">481 </span>  <span class="Conceal">¦</span> redraw-screen?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">12/ctrl-l</span>
+<span id="L482" class="LineNr">482 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> redraw-screen?
+<span id="L483" class="LineNr">483 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L484" class="LineNr">484 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L53'>sync-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L485" class="LineNr">485 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L486" class="LineNr">486 </span>  <span class="Delimiter">}</span>
+<span id="L487" class="LineNr">487 </span>]
+<span id="L488" class="LineNr">488 </span>
+<span id="L489" class="LineNr">489 </span><span class="Comment"># ctrl-n - switch focus</span>
+<span id="L490" class="LineNr">490 </span><span class="Comment"># todo: test this</span>
+<span id="L491" class="LineNr">491 </span>
+<span id="L492" class="LineNr">492 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L66'>&lt;global-type&gt;</a></span> [
+<span id="L493" class="LineNr">493 </span>  <span class="Delimiter">{</span>
+<span id="L494" class="LineNr">494 </span>  <span class="Conceal">¦</span> switch-side?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">14/ctrl-n</span>
+<span id="L495" class="LineNr">495 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> switch-side?
+<span id="L496" class="LineNr">496 </span>  <span class="Conceal">¦</span> sandbox-in-focus?:bool <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox-in-focus?:offset</span>
+<span id="L497" class="LineNr">497 </span>  <span class="Conceal">¦</span> sandbox-in-focus? <span class="Special">&lt;-</span> not sandbox-in-focus?
+<span id="L498" class="LineNr">498 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, sandbox-in-focus?
+<span id="L499" class="LineNr">499 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L500" class="LineNr">500 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
 <span id="L501" class="LineNr">501 </span>  <span class="Delimiter">}</span>
 <span id="L502" class="LineNr">502 </span>]
+<span id="L503" class="LineNr">503 </span>
+<span id="L504" class="LineNr">504 </span><span class="SalientComment">## helpers</span>
+<span id="L505" class="LineNr">505 </span>
+<span id="L506" class="LineNr">506 </span><span class="muRecipe">def</span> <a href='004-programming-environment.mu.html#L506'>draw-vertical</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, col:num, y:num, bottom:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L507" class="LineNr">507 </span>  <span class="Constant">local-scope</span>
+<span id="L508" class="LineNr">508 </span>  <span class="Constant">load-ingredients</span>
+<span id="L509" class="LineNr">509 </span>  style:char, style-found?:bool <span class="Special">&lt;-</span> <span class="Constant">next-ingredient</span>
+<span id="L510" class="LineNr">510 </span>  <span class="Delimiter">{</span>
+<span id="L511" class="LineNr">511 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> style-found?
+<span id="L512" class="LineNr">512 </span>  <span class="Conceal">¦</span> style <span class="Special">&lt;-</span> copy <span class="Constant">9474/vertical</span>
+<span id="L513" class="LineNr">513 </span>  <span class="Delimiter">}</span>
+<span id="L514" class="LineNr">514 </span>  color:num, color-found?:bool <span class="Special">&lt;-</span> <span class="Constant">next-ingredient</span>
+<span id="L515" class="LineNr">515 </span>  <span class="Delimiter">{</span>
+<span id="L516" class="LineNr">516 </span>  <span class="Conceal">¦</span> <span class="Comment"># default color to white</span>
+<span id="L517" class="LineNr">517 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> color-found?
+<span id="L518" class="LineNr">518 </span>  <span class="Conceal">¦</span> color <span class="Special">&lt;-</span> copy <span class="Constant">245/grey</span>
+<span id="L519" class="LineNr">519 </span>  <span class="Delimiter">}</span>
+<span id="L520" class="LineNr">520 </span>  <span class="Delimiter">{</span>
+<span id="L521" class="LineNr">521 </span>  <span class="Conceal">¦</span> continue?:bool <span class="Special">&lt;-</span> lesser-than y, bottom
+<span id="L522" class="LineNr">522 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> continue?
+<span id="L523" class="LineNr">523 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, y, col
+<span id="L524" class="LineNr">524 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, style, color
+<span id="L525" class="LineNr">525 </span>  <span class="Conceal">¦</span> y <span class="Special">&lt;-</span> add y,<span class="Constant"> 1</span>
+<span id="L526" class="LineNr">526 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L527" class="LineNr">527 </span>  <span class="Delimiter">}</span>
+<span id="L528" class="LineNr">528 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/005-sandbox.mu.html b/html/edit/005-sandbox.mu.html
index cc3613d8..30ea06c6 100644
--- a/html/edit/005-sandbox.mu.html
+++ b/html/edit/005-sandbox.mu.html
@@ -75,7 +75,7 @@ if ('onhashchange' in window) {
 <span id="L12" class="LineNr">  12 </span>  open-console
 <span id="L13" class="LineNr">  13 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <span class="Constant">0/filesystem</span>, <span class="Constant">0/screen</span>
 <span id="L14" class="LineNr">  14 </span>  env <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L504'>restore-sandboxes</a> env
-<span id="L15" class="LineNr">  15 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <span class="Constant">0/screen</span>, env, <a href='001-editor.mu.html#L121'>render</a>
+<span id="L15" class="LineNr">  15 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <span class="Constant">0/screen</span>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L16" class="LineNr">  16 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, env, <span class="Constant">0/filesystem</span>
 <span id="L17" class="LineNr">  17 </span>  <span class="Comment"># never gets here</span>
 <span id="L18" class="LineNr">  18 </span>]
@@ -185,7 +185,7 @@ if ('onhashchange' in window) {
 <span id="L122" class="LineNr"> 122 </span>  ]
 <span id="L123" class="LineNr"> 123 </span>]
 <span id="L124" class="LineNr"> 124 </span>
-<span id="L125" class="LineNr"> 125 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L57'>&lt;global-keypress&gt;</a></span> [
+<span id="L125" class="LineNr"> 125 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
 <span id="L126" class="LineNr"> 126 </span>  <span class="Comment"># F4? load all code and run all sandboxes.</span>
 <span id="L127" class="LineNr"> 127 </span>  <span class="Delimiter">{</span>
 <span id="L128" class="LineNr"> 128 </span>  <span class="Conceal">¦</span> do-run?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65532/F4</span>
@@ -193,12 +193,12 @@ if ('onhashchange' in window) {
 <span id="L130" class="LineNr"> 130 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L213'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[running...       ]</span>, <span class="Constant">245/grey</span>
 <span id="L131" class="LineNr"> 131 </span>  <span class="Conceal">¦</span> error?:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L143'>run-sandboxes</a> env, <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>
 <span id="L132" class="LineNr"> 132 </span>  <span class="Conceal">¦</span> <span class="Comment"># F4 might update warnings and results on both sides</span>
-<span id="L133" class="LineNr"> 133 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
+<span id="L133" class="LineNr"> 133 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L134" class="LineNr"> 134 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
 <span id="L135" class="LineNr"> 135 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> error?
 <span id="L136" class="LineNr"> 136 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L213'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[                 ]</span>, <span class="Constant">245/grey</span>
 <span id="L137" class="LineNr"> 137 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L138" class="LineNr"> 138 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L138" class="LineNr"> 138 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
 <span id="L139" class="LineNr"> 139 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
 <span id="L140" class="LineNr"> 140 </span>  <span class="Delimiter">}</span>
 <span id="L141" class="LineNr"> 141 </span>]
@@ -276,7 +276,7 @@ if ('onhashchange' in window) {
 <span id="L213" class="LineNr"> 213 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L213'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, msg:text, color:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
 <span id="L214" class="LineNr"> 214 </span>  <span class="Constant">local-scope</span>
 <span id="L215" class="LineNr"> 215 </span>  <span class="Constant">load-ingredients</span>
-<span id="L216" class="LineNr"> 216 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>,<span class="Constant"> 0</span>,<span class="Constant"> 2</span>
+<span id="L216" class="LineNr"> 216 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>,<span class="Constant"> 0</span>,<span class="Constant"> 2</span>
 <span id="L217" class="LineNr"> 217 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> print <a href='../081print.mu.html#L4'>screen</a>, msg, color, <span class="Constant">238/grey/background</span>
 <span id="L218" class="LineNr"> 218 </span>]
 <span id="L219" class="LineNr"> 219 </span>
@@ -314,35 +314,35 @@ if ('onhashchange' in window) {
 <span id="L251" class="LineNr"> 251 </span>  <span class="Conceal">¦</span> render-current-sandbox?:bool <span class="Special">&lt;-</span> equal render-from,<span class="Constant"> -1</span>
 <span id="L252" class="LineNr"> 252 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> render-current-sandbox?
 <span id="L253" class="LineNr"> 253 </span>  <span class="Conceal">¦</span> row, column, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox <span class="Special">&lt;-</span> call render-editor, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox
-<span id="L254" class="LineNr"> 254 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L221'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, column, left, right
+<span id="L254" class="LineNr"> 254 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L223'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, column, left, right
 <span id="L255" class="LineNr"> 255 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
 <span id="L256" class="LineNr"> 256 </span>  <span class="Delimiter">}</span>
 <span id="L257" class="LineNr"> 257 </span>  <span class="Comment"># render sandboxes</span>
 <span id="L258" class="LineNr"> 258 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
 <span id="L259" class="LineNr"> 259 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
 <span id="L260" class="LineNr"> 260 </span>  row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L264'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox, left, right, row, render-from
-<span id="L261" class="LineNr"> 261 </span>  <a href='001-editor.mu.html#L236'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
+<span id="L261" class="LineNr"> 261 </span>  <a href='001-editor.mu.html#L238'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
 <span id="L262" class="LineNr"> 262 </span>]
 <span id="L263" class="LineNr"> 263 </span>
 <span id="L264" class="LineNr"> 264 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L264'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox:&amp;:sandbox, left:num, right:num, row:num, render-from:num, idx:num<span class="muRecipe"> -&gt; </span>row:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox:&amp;:sandbox [
 <span id="L265" class="LineNr"> 265 </span>  <span class="Constant">local-scope</span>
 <span id="L266" class="LineNr"> 266 </span>  <span class="Constant">load-ingredients</span>
 <span id="L267" class="LineNr"> 267 </span>  <span class="muControl">return-unless</span> sandbox
-<span id="L268" class="LineNr"> 268 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L269" class="LineNr"> 269 </span>  at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L268" class="LineNr"> 268 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L269" class="LineNr"> 269 </span>  at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L270" class="LineNr"> 270 </span>  <span class="muControl">return-if</span> at-bottom?:bool
 <span id="L271" class="LineNr"> 271 </span>  hidden?:bool <span class="Special">&lt;-</span> lesser-than idx, render-from
 <span id="L272" class="LineNr"> 272 </span>  <span class="Delimiter">{</span>
 <span id="L273" class="LineNr"> 273 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> hidden?
 <span id="L274" class="LineNr"> 274 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox menu</span>
 <span id="L275" class="LineNr"> 275 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L276" class="LineNr"> 276 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L276" class="LineNr"> 276 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
 <span id="L277" class="LineNr"> 277 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L319'>render-sandbox-menu</a> <a href='../081print.mu.html#L4'>screen</a>, idx, left, right
 <span id="L278" class="LineNr"> 278 </span>  <span class="Conceal">¦</span> <span class="Comment"># save menu row so we can detect clicks to it later</span>
 <span id="L279" class="LineNr"> 279 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">starting-row-on-screen:offset</span>, row
 <span id="L280" class="LineNr"> 280 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox contents</span>
 <span id="L281" class="LineNr"> 281 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L282" class="LineNr"> 282 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L282" class="LineNr"> 282 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
 <span id="L283" class="LineNr"> 283 </span>  <span class="Conceal">¦</span> sandbox-data:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
 <span id="L284" class="LineNr"> 284 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L439'>render-code</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-data, left, right, row
 <span id="L285" class="LineNr"> 285 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>, row
@@ -351,7 +351,7 @@ if ('onhashchange' in window) {
 <span id="L288" class="LineNr"> 288 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L288'>&lt;render-sandbox-results&gt;</a></span>
 <span id="L289" class="LineNr"> 289 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
 <span id="L290" class="LineNr"> 290 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> sandbox-screen:&amp;:<a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> get *sandbox, <span class="Constant"><a href='../081print.mu.html#L4'>screen</a>:offset</span>
-<span id="L291" class="LineNr"> 291 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> empty-screen?:bool <span class="Special">&lt;-</span> <a href='../081print.mu.html#L53'>fake-screen-is-empty?</a> sandbox-screen
+<span id="L291" class="LineNr"> 291 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> empty-screen?:bool <span class="Special">&lt;-</span> <a href='../081print.mu.html#L60'>fake-screen-is-empty?</a> sandbox-screen
 <span id="L292" class="LineNr"> 292 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> empty-screen?
 <span id="L293" class="LineNr"> 293 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L538'>render-screen</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-screen, left, right, row
 <span id="L294" class="LineNr"> 294 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
@@ -361,7 +361,7 @@ if ('onhashchange' in window) {
 <span id="L298" class="LineNr"> 298 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">245/grey</span>, row
 <span id="L299" class="LineNr"> 299 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
 <span id="L300" class="LineNr"> 300 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +render-sandbox-end</span>
-<span id="L301" class="LineNr"> 301 </span>  <span class="Conceal">¦</span> at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L301" class="LineNr"> 301 </span>  <span class="Conceal">¦</span> at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L302" class="LineNr"> 302 </span>  <span class="Conceal">¦</span> <span class="muControl">return-if</span> at-bottom?
 <span id="L303" class="LineNr"> 303 </span>  <span class="Conceal">¦</span> <span class="Comment"># draw solid line after sandbox</span>
 <span id="L304" class="LineNr"> 304 </span>  <span class="Conceal">¦</span> <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
@@ -382,23 +382,23 @@ if ('onhashchange' in window) {
 <span id="L319" class="LineNr"> 319 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L319'>render-sandbox-menu</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox-index:num, left:num, right:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
 <span id="L320" class="LineNr"> 320 </span>  <span class="Constant">local-scope</span>
 <span id="L321" class="LineNr"> 321 </span>  <span class="Constant">load-ingredients</span>
-<span id="L322" class="LineNr"> 322 </span>  <a href='../081print.mu.html#L567'>move-cursor-to-column</a> <a href='../081print.mu.html#L4'>screen</a>, left
+<span id="L322" class="LineNr"> 322 </span>  <a href='../081print.mu.html#L574'>move-cursor-to-column</a> <a href='../081print.mu.html#L4'>screen</a>, left
 <span id="L323" class="LineNr"> 323 </span>  edit-button-left:num, edit-button-right:num, copy-button-left:num, copy-button-right:num, delete-button-left:num <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L344'>sandbox-menu-columns</a> left, right
 <span id="L324" class="LineNr"> 324 </span>  print <a href='../081print.mu.html#L4'>screen</a>, sandbox-index, <span class="Constant">232/dark-grey</span>, <span class="Constant">245/grey</span>
 <span id="L325" class="LineNr"> 325 </span>  start-buttons:num <span class="Special">&lt;-</span> subtract edit-button-left,<span class="Constant"> 1</span>
-<span id="L326" class="LineNr"> 326 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, start-buttons, <span class="Constant">245/grey</span>
+<span id="L326" class="LineNr"> 326 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, start-buttons, <span class="Constant">245/grey</span>
 <span id="L327" class="LineNr"> 327 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[edit]</span>, <span class="Constant">232/black</span>, <span class="Constant">94/background-orange</span>
-<span id="L328" class="LineNr"> 328 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, edit-button-right, <span class="Constant">94/background-orange</span>
-<span id="L329" class="LineNr"> 329 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L421'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L328" class="LineNr"> 328 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, edit-button-right, <span class="Constant">94/background-orange</span>
+<span id="L329" class="LineNr"> 329 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L428'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L330" class="LineNr"> 330 </span>  at-start-of-copy-button?:bool <span class="Special">&lt;-</span> equal col, copy-button-left
 <span id="L331" class="LineNr"> 331 </span>  assert at-start-of-copy-button?, <span class="Constant">[aaa]</span>
 <span id="L332" class="LineNr"> 332 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[copy]</span>, <span class="Constant">232/black</span>, <span class="Constant">58/background-green</span>
-<span id="L333" class="LineNr"> 333 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, copy-button-right, <span class="Constant">58/background-green</span>
-<span id="L334" class="LineNr"> 334 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L421'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L333" class="LineNr"> 333 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, copy-button-right, <span class="Constant">58/background-green</span>
+<span id="L334" class="LineNr"> 334 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L428'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L335" class="LineNr"> 335 </span>  at-start-of-delete-button?:bool <span class="Special">&lt;-</span> equal col, delete-button-left
 <span id="L336" class="LineNr"> 336 </span>  assert at-start-of-delete-button?, <span class="Constant">[bbb]</span>
 <span id="L337" class="LineNr"> 337 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[delete]</span>, <span class="Constant">232/black</span>, <span class="Constant">52/background-red</span>
-<span id="L338" class="LineNr"> 338 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right, <span class="Constant">52/background-red</span>
+<span id="L338" class="LineNr"> 338 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right, <span class="Constant">52/background-red</span>
 <span id="L339" class="LineNr"> 339 </span>]
 <span id="L340" class="LineNr"> 340 </span>
 <span id="L341" class="LineNr"> 341 </span><span class="Comment"># divide up the menu bar for a sandbox into 3 segments, for edit/copy/delete buttons</span>
@@ -426,15 +426,15 @@ if ('onhashchange' in window) {
 <span id="L363" class="LineNr"> 363 </span>  <span class="Constant">load-ingredients</span>
 <span id="L364" class="LineNr"> 364 </span>  <span class="muControl">return-unless</span> s
 <span id="L365" class="LineNr"> 365 </span>  column:num <span class="Special">&lt;-</span> copy left
-<span id="L366" class="LineNr"> 366 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L367" class="LineNr"> 367 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L366" class="LineNr"> 366 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L367" class="LineNr"> 367 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L368" class="LineNr"> 368 </span>  i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
 <span id="L369" class="LineNr"> 369 </span>  len:num <span class="Special">&lt;-</span> length *s
 <span id="L370" class="LineNr"> 370 </span>  <span class="Delimiter">{</span>
 <span id="L371" class="LineNr"> 371 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
 <span id="L372" class="LineNr"> 372 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal i, len
 <span id="L373" class="LineNr"> 373 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L374" class="LineNr"> 374 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L374" class="LineNr"> 374 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L375" class="LineNr"> 375 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
 <span id="L376" class="LineNr"> 376 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> index *s, i
 <span id="L377" class="LineNr"> 377 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
@@ -452,7 +452,7 @@ if ('onhashchange' in window) {
 <span id="L389" class="LineNr"> 389 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
 <span id="L390" class="LineNr"> 390 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
 <span id="L391" class="LineNr"> 391 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L392" class="LineNr"> 392 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L392" class="LineNr"> 392 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
 <span id="L393" class="LineNr"> 393 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
 <span id="L394" class="LineNr"> 394 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
 <span id="L395" class="LineNr"> 395 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
@@ -465,7 +465,7 @@ if ('onhashchange' in window) {
 <span id="L402" class="LineNr"> 402 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
 <span id="L403" class="LineNr"> 403 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
 <span id="L404" class="LineNr"> 404 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L405" class="LineNr"> 405 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L405" class="LineNr"> 405 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
 <span id="L406" class="LineNr"> 406 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># don't increment i</span>
 <span id="L407" class="LineNr"> 407 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
 <span id="L408" class="LineNr"> 408 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
@@ -475,12 +475,12 @@ if ('onhashchange' in window) {
 <span id="L412" class="LineNr"> 412 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
 <span id="L413" class="LineNr"> 413 </span>  <span class="Delimiter">}</span>
 <span id="L414" class="LineNr"> 414 </span>  was-at-left?:bool <span class="Special">&lt;-</span> equal column, left
-<span id="L415" class="LineNr"> 415 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L415" class="LineNr"> 415 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
 <span id="L416" class="LineNr"> 416 </span>  <span class="Delimiter">{</span>
 <span id="L417" class="LineNr"> 417 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> was-at-left?
 <span id="L418" class="LineNr"> 418 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
 <span id="L419" class="LineNr"> 419 </span>  <span class="Delimiter">}</span>
-<span id="L420" class="LineNr"> 420 </span>  <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L420" class="LineNr"> 420 </span>  <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
 <span id="L421" class="LineNr"> 421 </span>]
 <span id="L422" class="LineNr"> 422 </span>
 <span id="L423" class="LineNr"> 423 </span><span class="muScenario">scenario</span> read-text-wraps-barely-long-lines [
@@ -505,15 +505,15 @@ if ('onhashchange' in window) {
 <span id="L442" class="LineNr"> 442 </span>  <span class="muControl">return-unless</span> s
 <span id="L443" class="LineNr"> 443 </span>  color:num <span class="Special">&lt;-</span> copy <span class="Constant">7/white</span>
 <span id="L444" class="LineNr"> 444 </span>  column:num <span class="Special">&lt;-</span> copy left
-<span id="L445" class="LineNr"> 445 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L446" class="LineNr"> 446 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L445" class="LineNr"> 445 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L446" class="LineNr"> 446 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L447" class="LineNr"> 447 </span>  i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
 <span id="L448" class="LineNr"> 448 </span>  len:num <span class="Special">&lt;-</span> length *s
 <span id="L449" class="LineNr"> 449 </span>  <span class="Delimiter">{</span>
 <span id="L450" class="LineNr"> 450 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
 <span id="L451" class="LineNr"> 451 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal i, len
 <span id="L452" class="LineNr"> 452 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L453" class="LineNr"> 453 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L453" class="LineNr"> 453 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L454" class="LineNr"> 454 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
 <span id="L455" class="LineNr"> 455 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> index *s, i
 <span id="L456" class="LineNr"> 456 </span>  <span class="Conceal">¦</span> <span class="Constant">&lt;character-c-received&gt;</span>  <span class="Comment"># only line different from 'render-text'</span>
@@ -532,7 +532,7 @@ if ('onhashchange' in window) {
 <span id="L469" class="LineNr"> 469 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
 <span id="L470" class="LineNr"> 470 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
 <span id="L471" class="LineNr"> 471 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L472" class="LineNr"> 472 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L472" class="LineNr"> 472 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
 <span id="L473" class="LineNr"> 473 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
 <span id="L474" class="LineNr"> 474 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
 <span id="L475" class="LineNr"> 475 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
@@ -545,7 +545,7 @@ if ('onhashchange' in window) {
 <span id="L482" class="LineNr"> 482 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
 <span id="L483" class="LineNr"> 483 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
 <span id="L484" class="LineNr"> 484 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L485" class="LineNr"> 485 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L485" class="LineNr"> 485 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
 <span id="L486" class="LineNr"> 486 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># don't increment i</span>
 <span id="L487" class="LineNr"> 487 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
 <span id="L488" class="LineNr"> 488 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
@@ -555,12 +555,12 @@ if ('onhashchange' in window) {
 <span id="L492" class="LineNr"> 492 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
 <span id="L493" class="LineNr"> 493 </span>  <span class="Delimiter">}</span>
 <span id="L494" class="LineNr"> 494 </span>  was-at-left?:bool <span class="Special">&lt;-</span> equal column, left
-<span id="L495" class="LineNr"> 495 </span>  <a href='../081print.mu.html#L401'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L495" class="LineNr"> 495 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
 <span id="L496" class="LineNr"> 496 </span>  <span class="Delimiter">{</span>
 <span id="L497" class="LineNr"> 497 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> was-at-left?
 <span id="L498" class="LineNr"> 498 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
 <span id="L499" class="LineNr"> 499 </span>  <span class="Delimiter">}</span>
-<span id="L500" class="LineNr"> 500 </span>  <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L500" class="LineNr"> 500 </span>  <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
 <span id="L501" class="LineNr"> 501 </span>]
 <span id="L502" class="LineNr"> 502 </span>
 <span id="L503" class="LineNr"> 503 </span><span class="Comment"># assumes programming environment has no sandboxes; restores them from previous session</span>
@@ -604,24 +604,24 @@ if ('onhashchange' in window) {
 <span id="L541" class="LineNr"> 541 </span>  <span class="muControl">return-unless</span> sandbox-screen
 <span id="L542" class="LineNr"> 542 </span>  <span class="Comment"># print 'screen:'</span>
 <span id="L543" class="LineNr"> 543 </span>  row <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[screen:]</span>, left, right, <span class="Constant">245/grey</span>, row
-<span id="L544" class="LineNr"> 544 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L435'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L544" class="LineNr"> 544 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
 <span id="L545" class="LineNr"> 545 </span>  <span class="Comment"># start printing sandbox-screen</span>
 <span id="L546" class="LineNr"> 546 </span>  column:num <span class="Special">&lt;-</span> copy left
-<span id="L547" class="LineNr"> 547 </span>  s-width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L574'>screen-width</a> sandbox-screen
-<span id="L548" class="LineNr"> 548 </span>  s-height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> sandbox-screen
+<span id="L547" class="LineNr"> 547 </span>  s-width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> sandbox-screen
+<span id="L548" class="LineNr"> 548 </span>  s-height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> sandbox-screen
 <span id="L549" class="LineNr"> 549 </span>  buf:&amp;:@:<a href='../081print.mu.html#L12'>screen-cell</a> <span class="Special">&lt;-</span> get *sandbox-screen, <span class="Constant">data:offset</span>
 <span id="L550" class="LineNr"> 550 </span>  stop-printing:num <span class="Special">&lt;-</span> add left, s-width,<span class="Constant"> 3</span>
 <span id="L551" class="LineNr"> 551 </span>  max-column:num <span class="Special">&lt;-</span> min stop-printing, right
 <span id="L552" class="LineNr"> 552 </span>  i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
 <span id="L553" class="LineNr"> 553 </span>  len:num <span class="Special">&lt;-</span> length *buf
-<span id="L554" class="LineNr"> 554 </span>  <a href='../081print.mu.html#L587'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L587'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L554" class="LineNr"> 554 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L555" class="LineNr"> 555 </span>  <span class="Delimiter">{</span>
 <span id="L556" class="LineNr"> 556 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal i, len
 <span id="L557" class="LineNr"> 557 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L558" class="LineNr"> 558 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L587'>screen-height</a>
+<span id="L558" class="LineNr"> 558 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
 <span id="L559" class="LineNr"> 559 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
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+<span id="L765" class="LineNr"> 765 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L766" class="LineNr"> 766 </span>  assume-console [
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 <span id="L788" class="LineNr"> 788 </span>  recipe-bottom:num
 <span id="L789" class="LineNr"> 789 </span>]
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+<span id="L791" class="LineNr"> 791 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L437'>&lt;render-recipe-components-end&gt;</a></span> [
 <span id="L792" class="LineNr"> 792 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">recipe-bottom:offset</span>, row
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 <span id="L797" class="LineNr"> 797 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
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+<span id="L834" class="LineNr"> 834 </span>  height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
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 <span id="L876" class="LineNr"> 876 </span>  <span class="Conceal">¦</span> press enter
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-<span id="L998" class="LineNr"> 998 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-up?
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-<span id="L1020" class="LineNr">1020 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal <a href='../065duplex_list.mu.html#L29'>next</a>, in
-<span id="L1021" class="LineNr">1021 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
-<span id="L1022" class="LineNr">1022 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L29'>next</a>
-<span id="L1023" class="LineNr">1023 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L29'>next</a> <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
-<span id="L1024" class="LineNr">1024 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L1025" class="LineNr">1025 </span>  <span class="Delimiter">}</span>
-<span id="L1026" class="LineNr">1026 </span>  <span class="muControl">return</span> curr
-<span id="L1027" class="LineNr">1027 </span>]
-<span id="L1028" class="LineNr">1028 </span>
-<span id="L1029" class="LineNr">1029 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-on-recipe-side [
-<span id="L1030" class="LineNr">1030 </span>  <span class="Constant">local-scope</span>
-<span id="L1031" class="LineNr">1031 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L1032" class="LineNr">1032 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L1033" class="LineNr">1033 </span>  <span class="Comment"># initialize sandbox side and create a sandbox</span>
-<span id="L1034" class="LineNr">1034 </span>  assume-resources [
-<span id="L1035" class="LineNr">1035 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L1036" class="LineNr">1036 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">||</span>  <span class="Comment"># file containing just a newline</span>
-<span id="L1037" class="LineNr">1037 </span>  <span class="Conceal">¦</span> ]
-<span id="L1038" class="LineNr">1038 </span>  ]
-<span id="L1039" class="LineNr">1039 </span>  <span class="Comment"># create a sandbox</span>
-<span id="L1040" class="LineNr">1040 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 2, 2]</span>
-<span id="L1041" class="LineNr">1041 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L1042" class="LineNr">1042 </span>  assume-console [
-<span id="L1043" class="LineNr">1043 </span>  <span class="Conceal">¦</span> press F4
-<span id="L1044" class="LineNr">1044 </span>  ]
-<span id="L1045" class="LineNr">1045 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1046" class="LineNr">1046 </span>  <span class="Comment"># hit 'down' in recipe editor</span>
-<span id="L1047" class="LineNr">1047 </span>  assume-console [
-<span id="L1048" class="LineNr">1048 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L1049" class="LineNr">1049 </span>  ]
-<span id="L1050" class="LineNr">1050 </span>  run [
-<span id="L1051" class="LineNr">1051 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1052" class="LineNr">1052 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1053" class="LineNr">1053 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1054" class="LineNr">1054 </span>  ]
-<span id="L1055" class="LineNr">1055 </span>  <span class="Comment"># cursor doesn't move when the end is already on-screen</span>
-<span id="L1056" class="LineNr">1056 </span>  screen-should-contain [
-<span id="L1057" class="LineNr">1057 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1058" class="LineNr">1058 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣                                                 ╎                                                 .</span>
-<span id="L1059" class="LineNr">1059 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1060" class="LineNr">1060 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L1061" class="LineNr">1061 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1062" class="LineNr">1062 </span>  ]
-<span id="L1063" class="LineNr">1063 </span>]
-<span id="L1064" class="LineNr">1064 </span>
-<span id="L1065" class="LineNr">1065 </span><span class="muScenario">scenario</span> scrolling-through-multiple-sandboxes [
-<span id="L1066" class="LineNr">1066 </span>  <span class="Constant">local-scope</span>
-<span id="L1067" class="LineNr">1067 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L1068" class="LineNr">1068 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L1069" class="LineNr">1069 </span>  <span class="Comment"># initialize environment</span>
-<span id="L1070" class="LineNr">1070 </span>  assume-resources [
-<span id="L1071" class="LineNr">1071 </span>  ]
-<span id="L1072" class="LineNr">1072 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L1073" class="LineNr">1073 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L1074" class="LineNr">1074 </span>  <span class="Comment"># create 2 sandboxes</span>
-<span id="L1075" class="LineNr">1075 </span>  assume-console [
-<span id="L1076" class="LineNr">1076 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L1077" class="LineNr">1077 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L1078" class="LineNr">1078 </span>  <span class="Conceal">¦</span> press F4
-<span id="L1079" class="LineNr">1079 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
-<span id="L1080" class="LineNr">1080 </span>  <span class="Conceal">¦</span> press F4
-<span id="L1081" class="LineNr">1081 </span>  ]
-<span id="L1082" class="LineNr">1082 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1083" class="LineNr">1083 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1084" class="LineNr">1084 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1085" class="LineNr">1085 </span>  screen-should-contain [
-<span id="L1086" class="LineNr">1086 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1087" class="LineNr">1087 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
-<span id="L1088" class="LineNr">1088 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1089" class="LineNr">1089 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1090" class="LineNr">1090 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1091" class="LineNr">1091 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1092" class="LineNr">1092 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1093" class="LineNr">1093 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1094" class="LineNr">1094 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1095" class="LineNr">1095 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1096" class="LineNr">1096 </span>  ]
-<span id="L1097" class="LineNr">1097 </span>  <span class="Comment"># hit 'page-down'</span>
-<span id="L1098" class="LineNr">1098 </span>  assume-console [
-<span id="L1099" class="LineNr">1099 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L974" class="LineNr"> 974 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L975" class="LineNr"> 975 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L976" class="LineNr"> 976 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L977" class="LineNr"> 977 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L978" class="LineNr"> 978 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L979" class="LineNr"> 979 </span>  <span class="Delimiter">}</span>
+<span id="L980" class="LineNr"> 980 </span>]
+<span id="L981" class="LineNr"> 981 </span>
+<span id="L982" class="LineNr"> 982 </span><span class="Comment"># update-cursor takes render-from into account</span>
+<span id="L983" class="LineNr"> 983 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L463'>&lt;update-cursor-special-cases&gt;</a></span> [
+<span id="L984" class="LineNr"> 984 </span>  <span class="Delimiter">{</span>
+<span id="L985" class="LineNr"> 985 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
+<span id="L986" class="LineNr"> 986 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
+<span id="L987" class="LineNr"> 987 </span>  <span class="Conceal">¦</span> scrolling?:bool <span class="Special">&lt;-</span> greater-or-equal render-from,<span class="Constant"> 0</span>
+<span id="L988" class="LineNr"> 988 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> scrolling?
+<span id="L989" class="LineNr"> 989 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
+<span id="L990" class="LineNr"> 990 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">2/row</span>, cursor-column  <span class="Comment"># highlighted sandbox will always start at row 2</span>
+<span id="L991" class="LineNr"> 991 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
+<span id="L992" class="LineNr"> 992 </span>  <span class="Delimiter">}</span>
+<span id="L993" class="LineNr"> 993 </span>]
+<span id="L994" class="LineNr"> 994 </span>
+<span id="L995" class="LineNr"> 995 </span><span class="Comment"># 'page-up' on sandbox side is like 'page-down': updates render-from when necessary</span>
+<span id="L996" class="LineNr"> 996 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
+<span id="L997" class="LineNr"> 997 </span>  <span class="Delimiter">{</span>
+<span id="L998" class="LineNr"> 998 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
+<span id="L999" class="LineNr"> 999 </span>  <span class="Conceal">¦</span> page-up?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65519/page-up</span>
+<span id="L1000" class="LineNr">1000 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-up?
+<span id="L1001" class="LineNr">1001 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
+<span id="L1002" class="LineNr">1002 </span>  <span class="Conceal">¦</span> at-beginning?:bool <span class="Special">&lt;-</span> equal render-from,<span class="Constant"> -1</span>
+<span id="L1003" class="LineNr">1003 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> at-beginning?
+<span id="L1004" class="LineNr">1004 </span>  <span class="Conceal">¦</span> render-from <span class="Special">&lt;-</span> subtract render-from,<span class="Constant"> 1</span>
+<span id="L1005" class="LineNr">1005 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>, render-from
+<span id="L1006" class="LineNr">1006 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L1007" class="LineNr">1007 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L1008" class="LineNr">1008 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L1009" class="LineNr">1009 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L1010" class="LineNr">1010 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L1011" class="LineNr">1011 </span>  <span class="Delimiter">}</span>
+<span id="L1012" class="LineNr">1012 </span>]
+<span id="L1013" class="LineNr">1013 </span>
+<span id="L1014" class="LineNr">1014 </span><span class="Comment"># sandbox belonging to 'env' whose next-sandbox is 'in'</span>
+<span id="L1015" class="LineNr">1015 </span><span class="Comment"># return 0 if there's no such sandbox, either because 'in' doesn't exist in 'env', or because it's the first sandbox</span>
+<span id="L1016" class="LineNr">1016 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L1016'>previous-sandbox</a> env:&amp;:environment, in:&amp;:sandbox<span class="muRecipe"> -&gt; </span>out:&amp;:sandbox [
+<span id="L1017" class="LineNr">1017 </span>  <span class="Constant">local-scope</span>
+<span id="L1018" class="LineNr">1018 </span>  <span class="Constant">load-ingredients</span>
+<span id="L1019" class="LineNr">1019 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L1020" class="LineNr">1020 </span>  <span class="muControl">return-unless</span> curr, <span class="Constant">0/nil</span>
+<span id="L1021" class="LineNr">1021 </span>  <a href='../065duplex_list.mu.html#L29'>next</a>:&amp;:sandbox <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
+<span id="L1022" class="LineNr">1022 </span>  <span class="Delimiter">{</span>
+<span id="L1023" class="LineNr">1023 </span>  <span class="Conceal">¦</span> <span class="muControl">return-unless</span> <a href='../065duplex_list.mu.html#L29'>next</a>, <span class="Constant">0/nil</span>
+<span id="L1024" class="LineNr">1024 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal <a href='../065duplex_list.mu.html#L29'>next</a>, in
+<span id="L1025" class="LineNr">1025 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
+<span id="L1026" class="LineNr">1026 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L29'>next</a>
+<span id="L1027" class="LineNr">1027 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L29'>next</a> <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
+<span id="L1028" class="LineNr">1028 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L1029" class="LineNr">1029 </span>  <span class="Delimiter">}</span>
+<span id="L1030" class="LineNr">1030 </span>  <span class="muControl">return</span> curr
+<span id="L1031" class="LineNr">1031 </span>]
+<span id="L1032" class="LineNr">1032 </span>
+<span id="L1033" class="LineNr">1033 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-on-recipe-side [
+<span id="L1034" class="LineNr">1034 </span>  <span class="Constant">local-scope</span>
+<span id="L1035" class="LineNr">1035 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L1036" class="LineNr">1036 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L1037" class="LineNr">1037 </span>  <span class="Comment"># initialize sandbox side and create a sandbox</span>
+<span id="L1038" class="LineNr">1038 </span>  assume-resources [
+<span id="L1039" class="LineNr">1039 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L1040" class="LineNr">1040 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">||</span>  <span class="Comment"># file containing just a newline</span>
+<span id="L1041" class="LineNr">1041 </span>  <span class="Conceal">¦</span> ]
+<span id="L1042" class="LineNr">1042 </span>  ]
+<span id="L1043" class="LineNr">1043 </span>  <span class="Comment"># create a sandbox</span>
+<span id="L1044" class="LineNr">1044 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 2, 2]</span>
+<span id="L1045" class="LineNr">1045 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L1046" class="LineNr">1046 </span>  assume-console [
+<span id="L1047" class="LineNr">1047 </span>  <span class="Conceal">¦</span> press F4
+<span id="L1048" class="LineNr">1048 </span>  ]
+<span id="L1049" class="LineNr">1049 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1050" class="LineNr">1050 </span>  <span class="Comment"># hit 'down' in recipe editor</span>
+<span id="L1051" class="LineNr">1051 </span>  assume-console [
+<span id="L1052" class="LineNr">1052 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1053" class="LineNr">1053 </span>  ]
+<span id="L1054" class="LineNr">1054 </span>  run [
+<span id="L1055" class="LineNr">1055 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1056" class="LineNr">1056 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1057" class="LineNr">1057 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1058" class="LineNr">1058 </span>  ]
+<span id="L1059" class="LineNr">1059 </span>  <span class="Comment"># cursor doesn't move when the end is already on-screen</span>
+<span id="L1060" class="LineNr">1060 </span>  screen-should-contain [
+<span id="L1061" class="LineNr">1061 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1062" class="LineNr">1062 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣                                                 ╎                                                 .</span>
+<span id="L1063" class="LineNr">1063 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1064" class="LineNr">1064 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L1065" class="LineNr">1065 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1066" class="LineNr">1066 </span>  ]
+<span id="L1067" class="LineNr">1067 </span>]
+<span id="L1068" class="LineNr">1068 </span>
+<span id="L1069" class="LineNr">1069 </span><span class="muScenario">scenario</span> scrolling-through-multiple-sandboxes [
+<span id="L1070" class="LineNr">1070 </span>  <span class="Constant">local-scope</span>
+<span id="L1071" class="LineNr">1071 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L1072" class="LineNr">1072 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L1073" class="LineNr">1073 </span>  <span class="Comment"># initialize environment</span>
+<span id="L1074" class="LineNr">1074 </span>  assume-resources [
+<span id="L1075" class="LineNr">1075 </span>  ]
+<span id="L1076" class="LineNr">1076 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L1077" class="LineNr">1077 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L1078" class="LineNr">1078 </span>  <span class="Comment"># create 2 sandboxes</span>
+<span id="L1079" class="LineNr">1079 </span>  assume-console [
+<span id="L1080" class="LineNr">1080 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L1081" class="LineNr">1081 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
+<span id="L1082" class="LineNr">1082 </span>  <span class="Conceal">¦</span> press F4
+<span id="L1083" class="LineNr">1083 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L1084" class="LineNr">1084 </span>  <span class="Conceal">¦</span> press F4
+<span id="L1085" class="LineNr">1085 </span>  ]
+<span id="L1086" class="LineNr">1086 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1087" class="LineNr">1087 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1088" class="LineNr">1088 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1089" class="LineNr">1089 </span>  screen-should-contain [
+<span id="L1090" class="LineNr">1090 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1091" class="LineNr">1091 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
+<span id="L1092" class="LineNr">1092 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1093" class="LineNr">1093 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1094" class="LineNr">1094 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1095" class="LineNr">1095 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1096" class="LineNr">1096 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1097" class="LineNr">1097 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1098" class="LineNr">1098 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1099" class="LineNr">1099 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
 <span id="L1100" class="LineNr">1100 </span>  ]
-<span id="L1101" class="LineNr">1101 </span>  run [
-<span id="L1102" class="LineNr">1102 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1103" class="LineNr">1103 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1104" class="LineNr">1104 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1105" class="LineNr">1105 </span>  ]
-<span id="L1106" class="LineNr">1106 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
-<span id="L1107" class="LineNr">1107 </span>  <span class="Comment"># cursor moves to first sandbox</span>
-<span id="L1108" class="LineNr">1108 </span>  screen-should-contain [
-<span id="L1109" class="LineNr">1109 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1110" class="LineNr">1110 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1111" class="LineNr">1111 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
-<span id="L1112" class="LineNr">1112 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1113" class="LineNr">1113 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1101" class="LineNr">1101 </span>  <span class="Comment"># hit 'page-down'</span>
+<span id="L1102" class="LineNr">1102 </span>  assume-console [
+<span id="L1103" class="LineNr">1103 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1104" class="LineNr">1104 </span>  ]
+<span id="L1105" class="LineNr">1105 </span>  run [
+<span id="L1106" class="LineNr">1106 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1107" class="LineNr">1107 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1108" class="LineNr">1108 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1109" class="LineNr">1109 </span>  ]
+<span id="L1110" class="LineNr">1110 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+<span id="L1111" class="LineNr">1111 </span>  <span class="Comment"># cursor moves to first sandbox</span>
+<span id="L1112" class="LineNr">1112 </span>  screen-should-contain [
+<span id="L1113" class="LineNr">1113 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
 <span id="L1114" class="LineNr">1114 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1115" class="LineNr">1115 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1116" class="LineNr">1116 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1117" class="LineNr">1117 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1118" class="LineNr">1118 </span>  ]
-<span id="L1119" class="LineNr">1119 </span>  <span class="Comment"># hit 'page-down' again</span>
-<span id="L1120" class="LineNr">1120 </span>  assume-console [
-<span id="L1121" class="LineNr">1121 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1115" class="LineNr">1115 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
+<span id="L1116" class="LineNr">1116 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1117" class="LineNr">1117 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1118" class="LineNr">1118 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1119" class="LineNr">1119 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1120" class="LineNr">1120 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1121" class="LineNr">1121 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
 <span id="L1122" class="LineNr">1122 </span>  ]
-<span id="L1123" class="LineNr">1123 </span>  run [
-<span id="L1124" class="LineNr">1124 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1125" class="LineNr">1125 </span>  ]
-<span id="L1126" class="LineNr">1126 </span>  <span class="Comment"># just second sandbox displayed</span>
-<span id="L1127" class="LineNr">1127 </span>  screen-should-contain [
-<span id="L1128" class="LineNr">1128 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1129" class="LineNr">1129 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1130" class="LineNr">1130 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
-<span id="L1131" class="LineNr">1131 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1132" class="LineNr">1132 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1123" class="LineNr">1123 </span>  <span class="Comment"># hit 'page-down' again</span>
+<span id="L1124" class="LineNr">1124 </span>  assume-console [
+<span id="L1125" class="LineNr">1125 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1126" class="LineNr">1126 </span>  ]
+<span id="L1127" class="LineNr">1127 </span>  run [
+<span id="L1128" class="LineNr">1128 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1129" class="LineNr">1129 </span>  ]
+<span id="L1130" class="LineNr">1130 </span>  <span class="Comment"># just second sandbox displayed</span>
+<span id="L1131" class="LineNr">1131 </span>  screen-should-contain [
+<span id="L1132" class="LineNr">1132 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
 <span id="L1133" class="LineNr">1133 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1134" class="LineNr">1134 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1135" class="LineNr">1135 </span>  ]
-<span id="L1136" class="LineNr">1136 </span>  <span class="Comment"># hit 'page-down' again</span>
-<span id="L1137" class="LineNr">1137 </span>  assume-console [
-<span id="L1138" class="LineNr">1138 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1134" class="LineNr">1134 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
+<span id="L1135" class="LineNr">1135 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1136" class="LineNr">1136 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1137" class="LineNr">1137 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1138" class="LineNr">1138 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L1139" class="LineNr">1139 </span>  ]
-<span id="L1140" class="LineNr">1140 </span>  run [
-<span id="L1141" class="LineNr">1141 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1142" class="LineNr">1142 </span>  ]
-<span id="L1143" class="LineNr">1143 </span>  <span class="Comment"># no change</span>
-<span id="L1144" class="LineNr">1144 </span>  screen-should-contain [
-<span id="L1145" class="LineNr">1145 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1146" class="LineNr">1146 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1147" class="LineNr">1147 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
-<span id="L1148" class="LineNr">1148 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1149" class="LineNr">1149 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1140" class="LineNr">1140 </span>  <span class="Comment"># hit 'page-down' again</span>
+<span id="L1141" class="LineNr">1141 </span>  assume-console [
+<span id="L1142" class="LineNr">1142 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1143" class="LineNr">1143 </span>  ]
+<span id="L1144" class="LineNr">1144 </span>  run [
+<span id="L1145" class="LineNr">1145 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1146" class="LineNr">1146 </span>  ]
+<span id="L1147" class="LineNr">1147 </span>  <span class="Comment"># no change</span>
+<span id="L1148" class="LineNr">1148 </span>  screen-should-contain [
+<span id="L1149" class="LineNr">1149 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
 <span id="L1150" class="LineNr">1150 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1151" class="LineNr">1151 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1152" class="LineNr">1152 </span>  ]
-<span id="L1153" class="LineNr">1153 </span>  <span class="Comment"># hit 'page-up'</span>
-<span id="L1154" class="LineNr">1154 </span>  assume-console [
-<span id="L1155" class="LineNr">1155 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1151" class="LineNr">1151 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
+<span id="L1152" class="LineNr">1152 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1153" class="LineNr">1153 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1154" class="LineNr">1154 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1155" class="LineNr">1155 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L1156" class="LineNr">1156 </span>  ]
-<span id="L1157" class="LineNr">1157 </span>  run [
-<span id="L1158" class="LineNr">1158 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1159" class="LineNr">1159 </span>  ]
-<span id="L1160" class="LineNr">1160 </span>  <span class="Comment"># back to displaying both sandboxes without editor</span>
-<span id="L1161" class="LineNr">1161 </span>  screen-should-contain [
-<span id="L1162" class="LineNr">1162 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1163" class="LineNr">1163 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1164" class="LineNr">1164 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L1165" class="LineNr">1165 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1166" class="LineNr">1166 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1157" class="LineNr">1157 </span>  <span class="Comment"># hit 'page-up'</span>
+<span id="L1158" class="LineNr">1158 </span>  assume-console [
+<span id="L1159" class="LineNr">1159 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1160" class="LineNr">1160 </span>  ]
+<span id="L1161" class="LineNr">1161 </span>  run [
+<span id="L1162" class="LineNr">1162 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1163" class="LineNr">1163 </span>  ]
+<span id="L1164" class="LineNr">1164 </span>  <span class="Comment"># back to displaying both sandboxes without editor</span>
+<span id="L1165" class="LineNr">1165 </span>  screen-should-contain [
+<span id="L1166" class="LineNr">1166 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
 <span id="L1167" class="LineNr">1167 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1168" class="LineNr">1168 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1169" class="LineNr">1169 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1170" class="LineNr">1170 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1171" class="LineNr">1171 </span>  ]
-<span id="L1172" class="LineNr">1172 </span>  <span class="Comment"># hit 'page-up' again</span>
-<span id="L1173" class="LineNr">1173 </span>  assume-console [
-<span id="L1174" class="LineNr">1174 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1168" class="LineNr">1168 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L1169" class="LineNr">1169 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1170" class="LineNr">1170 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1171" class="LineNr">1171 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1172" class="LineNr">1172 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1173" class="LineNr">1173 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1174" class="LineNr">1174 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
 <span id="L1175" class="LineNr">1175 </span>  ]
-<span id="L1176" class="LineNr">1176 </span>  run [
-<span id="L1177" class="LineNr">1177 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1178" class="LineNr">1178 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1179" class="LineNr">1179 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1180" class="LineNr">1180 </span>  ]
-<span id="L1181" class="LineNr">1181 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
-<span id="L1182" class="LineNr">1182 </span>  screen-should-contain [
-<span id="L1183" class="LineNr">1183 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1184" class="LineNr">1184 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
-<span id="L1185" class="LineNr">1185 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1186" class="LineNr">1186 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1187" class="LineNr">1187 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1188" class="LineNr">1188 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1189" class="LineNr">1189 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1190" class="LineNr">1190 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1191" class="LineNr">1191 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1192" class="LineNr">1192 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1193" class="LineNr">1193 </span>  ]
-<span id="L1194" class="LineNr">1194 </span>  <span class="Comment"># hit 'page-up' again</span>
-<span id="L1195" class="LineNr">1195 </span>  assume-console [
-<span id="L1196" class="LineNr">1196 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1176" class="LineNr">1176 </span>  <span class="Comment"># hit 'page-up' again</span>
+<span id="L1177" class="LineNr">1177 </span>  assume-console [
+<span id="L1178" class="LineNr">1178 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1179" class="LineNr">1179 </span>  ]
+<span id="L1180" class="LineNr">1180 </span>  run [
+<span id="L1181" class="LineNr">1181 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1182" class="LineNr">1182 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1183" class="LineNr">1183 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1184" class="LineNr">1184 </span>  ]
+<span id="L1185" class="LineNr">1185 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
+<span id="L1186" class="LineNr">1186 </span>  screen-should-contain [
+<span id="L1187" class="LineNr">1187 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1188" class="LineNr">1188 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
+<span id="L1189" class="LineNr">1189 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1190" class="LineNr">1190 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1191" class="LineNr">1191 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1192" class="LineNr">1192 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1193" class="LineNr">1193 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1194" class="LineNr">1194 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1195" class="LineNr">1195 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1196" class="LineNr">1196 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
 <span id="L1197" class="LineNr">1197 </span>  ]
-<span id="L1198" class="LineNr">1198 </span>  run [
-<span id="L1199" class="LineNr">1199 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1200" class="LineNr">1200 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1201" class="LineNr">1201 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1202" class="LineNr">1202 </span>  ]
-<span id="L1203" class="LineNr">1203 </span>  <span class="Comment"># no change</span>
-<span id="L1204" class="LineNr">1204 </span>  screen-should-contain [
-<span id="L1205" class="LineNr">1205 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1206" class="LineNr">1206 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
-<span id="L1207" class="LineNr">1207 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1208" class="LineNr">1208 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1209" class="LineNr">1209 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1210" class="LineNr">1210 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1211" class="LineNr">1211 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1212" class="LineNr">1212 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1213" class="LineNr">1213 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1214" class="LineNr">1214 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1215" class="LineNr">1215 </span>  ]
-<span id="L1216" class="LineNr">1216 </span>]
-<span id="L1217" class="LineNr">1217 </span>
-<span id="L1218" class="LineNr">1218 </span><span class="muScenario">scenario</span> scrolling-manages-sandbox-index-correctly [
-<span id="L1219" class="LineNr">1219 </span>  <span class="Constant">local-scope</span>
-<span id="L1220" class="LineNr">1220 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L1221" class="LineNr">1221 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L1222" class="LineNr">1222 </span>  <span class="Comment"># initialize environment</span>
-<span id="L1223" class="LineNr">1223 </span>  assume-resources [
-<span id="L1224" class="LineNr">1224 </span>  ]
-<span id="L1225" class="LineNr">1225 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L1226" class="LineNr">1226 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L1227" class="LineNr">1227 </span>  <span class="Comment"># create a sandbox</span>
-<span id="L1228" class="LineNr">1228 </span>  assume-console [
-<span id="L1229" class="LineNr">1229 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L1230" class="LineNr">1230 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
-<span id="L1231" class="LineNr">1231 </span>  <span class="Conceal">¦</span> press F4
-<span id="L1232" class="LineNr">1232 </span>  ]
-<span id="L1233" class="LineNr">1233 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1234" class="LineNr">1234 </span>  screen-should-contain [
-<span id="L1235" class="LineNr">1235 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1236" class="LineNr">1236 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1237" class="LineNr">1237 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1238" class="LineNr">1238 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1239" class="LineNr">1239 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1240" class="LineNr">1240 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1241" class="LineNr">1241 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1242" class="LineNr">1242 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1243" class="LineNr">1243 </span>  ]
-<span id="L1244" class="LineNr">1244 </span>  <span class="Comment"># hit 'page-down' and 'page-up' a couple of times. sandbox index should be stable</span>
-<span id="L1245" class="LineNr">1245 </span>  assume-console [
-<span id="L1246" class="LineNr">1246 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1198" class="LineNr">1198 </span>  <span class="Comment"># hit 'page-up' again</span>
+<span id="L1199" class="LineNr">1199 </span>  assume-console [
+<span id="L1200" class="LineNr">1200 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1201" class="LineNr">1201 </span>  ]
+<span id="L1202" class="LineNr">1202 </span>  run [
+<span id="L1203" class="LineNr">1203 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1204" class="LineNr">1204 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1205" class="LineNr">1205 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1206" class="LineNr">1206 </span>  ]
+<span id="L1207" class="LineNr">1207 </span>  <span class="Comment"># no change</span>
+<span id="L1208" class="LineNr">1208 </span>  screen-should-contain [
+<span id="L1209" class="LineNr">1209 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1210" class="LineNr">1210 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
+<span id="L1211" class="LineNr">1211 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1212" class="LineNr">1212 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1213" class="LineNr">1213 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1214" class="LineNr">1214 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1215" class="LineNr">1215 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1216" class="LineNr">1216 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1217" class="LineNr">1217 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1218" class="LineNr">1218 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1219" class="LineNr">1219 </span>  ]
+<span id="L1220" class="LineNr">1220 </span>]
+<span id="L1221" class="LineNr">1221 </span>
+<span id="L1222" class="LineNr">1222 </span><span class="muScenario">scenario</span> scrolling-manages-sandbox-index-correctly [
+<span id="L1223" class="LineNr">1223 </span>  <span class="Constant">local-scope</span>
+<span id="L1224" class="LineNr">1224 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L1225" class="LineNr">1225 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L1226" class="LineNr">1226 </span>  <span class="Comment"># initialize environment</span>
+<span id="L1227" class="LineNr">1227 </span>  assume-resources [
+<span id="L1228" class="LineNr">1228 </span>  ]
+<span id="L1229" class="LineNr">1229 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L1230" class="LineNr">1230 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L1231" class="LineNr">1231 </span>  <span class="Comment"># create a sandbox</span>
+<span id="L1232" class="LineNr">1232 </span>  assume-console [
+<span id="L1233" class="LineNr">1233 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L1234" class="LineNr">1234 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L1235" class="LineNr">1235 </span>  <span class="Conceal">¦</span> press F4
+<span id="L1236" class="LineNr">1236 </span>  ]
+<span id="L1237" class="LineNr">1237 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1238" class="LineNr">1238 </span>  screen-should-contain [
+<span id="L1239" class="LineNr">1239 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1240" class="LineNr">1240 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1241" class="LineNr">1241 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1242" class="LineNr">1242 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1243" class="LineNr">1243 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1244" class="LineNr">1244 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1245" class="LineNr">1245 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1246" class="LineNr">1246 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L1247" class="LineNr">1247 </span>  ]
-<span id="L1248" class="LineNr">1248 </span>  run [
-<span id="L1249" class="LineNr">1249 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1250" class="LineNr">1250 </span>  ]
-<span id="L1251" class="LineNr">1251 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
-<span id="L1252" class="LineNr">1252 </span>  <span class="Comment"># cursor moves to first sandbox</span>
-<span id="L1253" class="LineNr">1253 </span>  screen-should-contain [
-<span id="L1254" class="LineNr">1254 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1255" class="LineNr">1255 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1256" class="LineNr">1256 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L1257" class="LineNr">1257 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1258" class="LineNr">1258 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1248" class="LineNr">1248 </span>  <span class="Comment"># hit 'page-down' and 'page-up' a couple of times. sandbox index should be stable</span>
+<span id="L1249" class="LineNr">1249 </span>  assume-console [
+<span id="L1250" class="LineNr">1250 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1251" class="LineNr">1251 </span>  ]
+<span id="L1252" class="LineNr">1252 </span>  run [
+<span id="L1253" class="LineNr">1253 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1254" class="LineNr">1254 </span>  ]
+<span id="L1255" class="LineNr">1255 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+<span id="L1256" class="LineNr">1256 </span>  <span class="Comment"># cursor moves to first sandbox</span>
+<span id="L1257" class="LineNr">1257 </span>  screen-should-contain [
+<span id="L1258" class="LineNr">1258 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
 <span id="L1259" class="LineNr">1259 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1260" class="LineNr">1260 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1261" class="LineNr">1261 </span>  ]
-<span id="L1262" class="LineNr">1262 </span>  <span class="Comment"># hit 'page-up' again</span>
-<span id="L1263" class="LineNr">1263 </span>  assume-console [
-<span id="L1264" class="LineNr">1264 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1260" class="LineNr">1260 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L1261" class="LineNr">1261 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1262" class="LineNr">1262 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1263" class="LineNr">1263 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1264" class="LineNr">1264 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L1265" class="LineNr">1265 </span>  ]
-<span id="L1266" class="LineNr">1266 </span>  run [
-<span id="L1267" class="LineNr">1267 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1268" class="LineNr">1268 </span>  ]
-<span id="L1269" class="LineNr">1269 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
-<span id="L1270" class="LineNr">1270 </span>  screen-should-contain [
-<span id="L1271" class="LineNr">1271 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1272" class="LineNr">1272 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1273" class="LineNr">1273 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1274" class="LineNr">1274 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1275" class="LineNr">1275 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1276" class="LineNr">1276 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1277" class="LineNr">1277 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1278" class="LineNr">1278 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1279" class="LineNr">1279 </span>  ]
-<span id="L1280" class="LineNr">1280 </span>  <span class="Comment"># hit 'page-down'</span>
-<span id="L1281" class="LineNr">1281 </span>  assume-console [
-<span id="L1282" class="LineNr">1282 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1266" class="LineNr">1266 </span>  <span class="Comment"># hit 'page-up' again</span>
+<span id="L1267" class="LineNr">1267 </span>  assume-console [
+<span id="L1268" class="LineNr">1268 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1269" class="LineNr">1269 </span>  ]
+<span id="L1270" class="LineNr">1270 </span>  run [
+<span id="L1271" class="LineNr">1271 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1272" class="LineNr">1272 </span>  ]
+<span id="L1273" class="LineNr">1273 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
+<span id="L1274" class="LineNr">1274 </span>  screen-should-contain [
+<span id="L1275" class="LineNr">1275 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1276" class="LineNr">1276 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1277" class="LineNr">1277 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1278" class="LineNr">1278 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1279" class="LineNr">1279 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1280" class="LineNr">1280 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1281" class="LineNr">1281 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1282" class="LineNr">1282 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L1283" class="LineNr">1283 </span>  ]
-<span id="L1284" class="LineNr">1284 </span>  run [
-<span id="L1285" class="LineNr">1285 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1286" class="LineNr">1286 </span>  ]
-<span id="L1287" class="LineNr">1287 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
-<span id="L1288" class="LineNr">1288 </span>  <span class="Comment"># cursor moves to first sandbox</span>
-<span id="L1289" class="LineNr">1289 </span>  screen-should-contain [
-<span id="L1290" class="LineNr">1290 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1291" class="LineNr">1291 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1292" class="LineNr">1292 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L1293" class="LineNr">1293 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1294" class="LineNr">1294 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1284" class="LineNr">1284 </span>  <span class="Comment"># hit 'page-down'</span>
+<span id="L1285" class="LineNr">1285 </span>  assume-console [
+<span id="L1286" class="LineNr">1286 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1287" class="LineNr">1287 </span>  ]
+<span id="L1288" class="LineNr">1288 </span>  run [
+<span id="L1289" class="LineNr">1289 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1290" class="LineNr">1290 </span>  ]
+<span id="L1291" class="LineNr">1291 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+<span id="L1292" class="LineNr">1292 </span>  <span class="Comment"># cursor moves to first sandbox</span>
+<span id="L1293" class="LineNr">1293 </span>  screen-should-contain [
+<span id="L1294" class="LineNr">1294 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
 <span id="L1295" class="LineNr">1295 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1296" class="LineNr">1296 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1297" class="LineNr">1297 </span>  ]
-<span id="L1298" class="LineNr">1298 </span>]
+<span id="L1296" class="LineNr">1296 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L1297" class="LineNr">1297 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1298" class="LineNr">1298 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1299" class="LineNr">1299 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1300" class="LineNr">1300 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1301" class="LineNr">1301 </span>  ]
+<span id="L1302" class="LineNr">1302 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/006-sandbox-copy.mu.html b/html/edit/006-sandbox-copy.mu.html
index d7d3192a..82d58cb3 100644
--- a/html/edit/006-sandbox-copy.mu.html
+++ b/html/edit/006-sandbox-copy.mu.html
@@ -183,160 +183,162 @@ if ('onhashchange' in window) {
 <span id="L121" class="LineNr">121 </span>  ]
 <span id="L122" class="LineNr">122 </span>]
 <span id="L123" class="LineNr">123 </span>
-<span id="L124" class="LineNr">124 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L76'>&lt;global-touch&gt;</a></span> [
+<span id="L124" class="LineNr">124 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L80'>&lt;global-touch&gt;</a></span> [
 <span id="L125" class="LineNr">125 </span>  <span class="Comment"># support 'copy' button</span>
 <span id="L126" class="LineNr">126 </span>  <span class="Delimiter">{</span>
-<span id="L127" class="LineNr">127 </span>  <span class="Conceal">¦</span> copy?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L138'>should-attempt-copy?</a> click-row, click-column, env
+<span id="L127" class="LineNr">127 </span>  <span class="Conceal">¦</span> copy?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L140'>should-attempt-copy?</a> click-row, click-column, env
 <span id="L128" class="LineNr">128 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> copy?
-<span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span> copy?, env <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L157'>try-copy-sandbox</a> click-row, env
+<span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span> copy?, env <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L159'>try-copy-sandbox</a> click-row, env
 <span id="L130" class="LineNr">130 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> copy?
-<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L134" class="LineNr">134 </span>  <span class="Delimiter">}</span>
-<span id="L135" class="LineNr">135 </span>]
-<span id="L136" class="LineNr">136 </span>
-<span id="L137" class="LineNr">137 </span><span class="Comment"># some preconditions for attempting to copy a sandbox</span>
-<span id="L138" class="LineNr">138 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L138'>should-attempt-copy?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
-<span id="L139" class="LineNr">139 </span>  <span class="Constant">local-scope</span>
-<span id="L140" class="LineNr">140 </span>  <span class="Constant">load-ingredients</span>
-<span id="L141" class="LineNr">141 </span>  <span class="Comment"># are we below the sandbox editor?</span>
-<span id="L142" class="LineNr">142 </span>  click-sandbox-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L188'>click-on-sandbox-area?</a> click-row, click-column, env
-<span id="L143" class="LineNr">143 </span>  <span class="muControl">return-unless</span> click-sandbox-area?, <span class="Constant">0/false</span>
-<span id="L144" class="LineNr">144 </span>  <span class="Comment"># narrower, is the click in the columns spanning the 'copy' button?</span>
-<span id="L145" class="LineNr">145 </span>  first-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L146" class="LineNr">146 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
-<span id="L147" class="LineNr">147 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
-<span id="L148" class="LineNr">148 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
-<span id="L149" class="LineNr">149 </span>  _, _, copy-button-left:num, copy-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L344'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
-<span id="L150" class="LineNr">150 </span>  copy-button-vertical-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L209'>within-range?</a> click-column, copy-button-left, copy-button-right
-<span id="L151" class="LineNr">151 </span>  <span class="muControl">return-unless</span> copy-button-vertical-area?, <span class="Constant">0/false</span>
-<span id="L152" class="LineNr">152 </span>  <span class="Comment"># finally, is sandbox editor empty?</span>
-<span id="L153" class="LineNr">153 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L154" class="LineNr">154 </span>  result <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L201'>empty-editor?</a> current-sandbox
-<span id="L155" class="LineNr">155 </span>]
-<span id="L156" class="LineNr">156 </span>
-<span id="L157" class="LineNr">157 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L157'>try-copy-sandbox</a> click-row:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>clicked-on-copy-button?:bool, env:&amp;:environment [
-<span id="L158" class="LineNr">158 </span>  <span class="Constant">local-scope</span>
-<span id="L159" class="LineNr">159 </span>  <span class="Constant">load-ingredients</span>
-<span id="L160" class="LineNr">160 </span>  <span class="Comment"># identify the sandbox to copy, if the click was actually on the 'copy' button</span>
-<span id="L161" class="LineNr">161 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L173'>find-sandbox</a> env, click-row
-<span id="L162" class="LineNr">162 </span>  <span class="muControl">return-unless</span> sandbox, <span class="Constant">0/false</span>
-<span id="L163" class="LineNr">163 </span>  clicked-on-copy-button? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-<span id="L164" class="LineNr">164 </span>  text:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
-<span id="L165" class="LineNr">165 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L166" class="LineNr">166 </span>  current-sandbox <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L71'>insert-text</a> current-sandbox, text
-<span id="L167" class="LineNr">167 </span>  <span class="Comment"># reset scroll</span>
-<span id="L168" class="LineNr">168 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>,<span class="Constant"> -1</span>
-<span id="L169" class="LineNr">169 </span>  <span class="Comment"># position cursor in sandbox editor</span>
-<span id="L170" class="LineNr">170 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, <span class="Constant">1/true</span>
-<span id="L171" class="LineNr">171 </span>]
-<span id="L172" class="LineNr">172 </span>
-<span id="L173" class="LineNr">173 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L173'>find-sandbox</a> env:&amp;:environment, click-row:num<span class="muRecipe"> -&gt; </span>result:&amp;:sandbox [
-<span id="L174" class="LineNr">174 </span>  <span class="Constant">local-scope</span>
-<span id="L175" class="LineNr">175 </span>  <span class="Constant">load-ingredients</span>
-<span id="L176" class="LineNr">176 </span>  curr-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L177" class="LineNr">177 </span>  <span class="Delimiter">{</span>
-<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr-sandbox
-<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span> start:num <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal click-row, start
-<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> <span class="muControl">return-if</span> found?, curr-sandbox
-<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> curr-sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L184" class="LineNr">184 </span>  <span class="Delimiter">}</span>
-<span id="L185" class="LineNr">185 </span>  <span class="muControl">return</span> <span class="Constant">0/not-found</span>
-<span id="L186" class="LineNr">186 </span>]
-<span id="L187" class="LineNr">187 </span>
-<span id="L188" class="LineNr">188 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L188'>click-on-sandbox-area?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
-<span id="L189" class="LineNr">189 </span>  <span class="Constant">local-scope</span>
-<span id="L190" class="LineNr">190 </span>  <span class="Constant">load-ingredients</span>
-<span id="L191" class="LineNr">191 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L192" class="LineNr">192 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
-<span id="L193" class="LineNr">193 </span>  on-sandbox-side?:bool <span class="Special">&lt;-</span> greater-or-equal click-column, sandbox-left-margin
-<span id="L194" class="LineNr">194 </span>  <span class="muControl">return-unless</span> on-sandbox-side?, <span class="Constant">0/false</span>
-<span id="L195" class="LineNr">195 </span>  first-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L196" class="LineNr">196 </span>  <span class="muControl">return-unless</span> first-sandbox, <span class="Constant">0/false</span>
-<span id="L197" class="LineNr">197 </span>  first-sandbox-begins:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-<span id="L198" class="LineNr">198 </span>  result <span class="Special">&lt;-</span> greater-or-equal click-row, first-sandbox-begins
-<span id="L199" class="LineNr">199 </span>]
-<span id="L200" class="LineNr">200 </span>
-<span id="L201" class="LineNr">201 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L201'>empty-editor?</a> editor:&amp;:editor<span class="muRecipe"> -&gt; </span>result:bool [
-<span id="L202" class="LineNr">202 </span>  <span class="Constant">local-scope</span>
-<span id="L203" class="LineNr">203 </span>  <span class="Constant">load-ingredients</span>
-<span id="L204" class="LineNr">204 </span>  head:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
-<span id="L205" class="LineNr">205 </span>  first:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> head
-<span id="L206" class="LineNr">206 </span>  result <span class="Special">&lt;-</span> not first
-<span id="L207" class="LineNr">207 </span>]
-<span id="L208" class="LineNr">208 </span>
-<span id="L209" class="LineNr">209 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L209'>within-range?</a> x:num, low:num, high:num<span class="muRecipe"> -&gt; </span>result:bool [
-<span id="L210" class="LineNr">210 </span>  <span class="Constant">local-scope</span>
-<span id="L211" class="LineNr">211 </span>  <span class="Constant">load-ingredients</span>
-<span id="L212" class="LineNr">212 </span>  not-too-far-left?:bool <span class="Special">&lt;-</span> greater-or-equal x, low
-<span id="L213" class="LineNr">213 </span>  not-too-far-right?:bool <span class="Special">&lt;-</span> lesser-or-equal x, high
-<span id="L214" class="LineNr">214 </span>  result <span class="Special">&lt;-</span> and not-too-far-left? not-too-far-right?
-<span id="L215" class="LineNr">215 </span>]
-<span id="L216" class="LineNr">216 </span>
-<span id="L217" class="LineNr">217 </span><span class="muScenario">scenario</span> copy-fails-if-sandbox-editor-not-empty [
-<span id="L218" class="LineNr">218 </span>  <span class="Constant">local-scope</span>
-<span id="L219" class="LineNr">219 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L220" class="LineNr">220 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L221" class="LineNr">221 </span>  <span class="Comment"># empty recipes</span>
-<span id="L222" class="LineNr">222 </span>  assume-resources [
-<span id="L223" class="LineNr">223 </span>  ]
-<span id="L224" class="LineNr">224 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 1, 1]</span>  <span class="Comment"># contents of sandbox editor</span>
-<span id="L225" class="LineNr">225 </span>  <span class="Comment"># run it</span>
-<span id="L226" class="LineNr">226 </span>  assume-console [
-<span id="L227" class="LineNr">227 </span>  <span class="Conceal">¦</span> press F4
-<span id="L228" class="LineNr">228 </span>  ]
-<span id="L229" class="LineNr">229 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L230" class="LineNr">230 </span>  screen-should-contain [
-<span id="L231" class="LineNr">231 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L232" class="LineNr">232 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L233" class="LineNr">233 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L234" class="LineNr">234 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L235" class="LineNr">235 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L236" class="LineNr">236 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L238" class="LineNr">238 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L239" class="LineNr">239 </span>  ]
-<span id="L240" class="LineNr">240 </span>  <span class="Comment"># type something into the sandbox editor, then click on the 'copy' button</span>
-<span id="L241" class="LineNr">241 </span>  assume-console [
-<span id="L242" class="LineNr">242 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 70</span>  <span class="Comment"># put cursor in sandbox editor</span>
-<span id="L243" class="LineNr">243 </span>  <span class="Conceal">¦</span> type <span class="Constant">[0]</span>  <span class="Comment"># type something</span>
-<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 70</span>  <span class="Comment"># click 'copy' button</span>
-<span id="L245" class="LineNr">245 </span>  ]
-<span id="L246" class="LineNr">246 </span>  run [
-<span id="L247" class="LineNr">247 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L248" class="LineNr">248 </span>  ]
-<span id="L249" class="LineNr">249 </span>  <span class="Comment"># copy doesn't happen</span>
-<span id="L250" class="LineNr">250 </span>  screen-should-contain [
-<span id="L251" class="LineNr">251 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L252" class="LineNr">252 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0                                                .</span>
-<span id="L253" class="LineNr">253 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L254" class="LineNr">254 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L255" class="LineNr">255 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L257" class="LineNr">257 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L258" class="LineNr">258 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L259" class="LineNr">259 </span>  ]
-<span id="L260" class="LineNr">260 </span>  <span class="Comment"># cursor should be in the right place</span>
-<span id="L261" class="LineNr">261 </span>  assume-console [
-<span id="L262" class="LineNr">262 </span>  <span class="Conceal">¦</span> type <span class="Constant">[1]</span>
-<span id="L263" class="LineNr">263 </span>  ]
-<span id="L264" class="LineNr">264 </span>  run [
-<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L266" class="LineNr">266 </span>  ]
-<span id="L267" class="LineNr">267 </span>  screen-should-contain [
-<span id="L268" class="LineNr">268 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L269" class="LineNr">269 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎01                                               .</span>
-<span id="L270" class="LineNr">270 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L272" class="LineNr">272 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L273" class="LineNr">273 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L274" class="LineNr">274 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L275" class="LineNr">275 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L276" class="LineNr">276 </span>  ]
-<span id="L277" class="LineNr">277 </span>]
+<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L135" class="LineNr">135 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L136" class="LineNr">136 </span>  <span class="Delimiter">}</span>
+<span id="L137" class="LineNr">137 </span>]
+<span id="L138" class="LineNr">138 </span>
+<span id="L139" class="LineNr">139 </span><span class="Comment"># some preconditions for attempting to copy a sandbox</span>
+<span id="L140" class="LineNr">140 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L140'>should-attempt-copy?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
+<span id="L141" class="LineNr">141 </span>  <span class="Constant">local-scope</span>
+<span id="L142" class="LineNr">142 </span>  <span class="Constant">load-ingredients</span>
+<span id="L143" class="LineNr">143 </span>  <span class="Comment"># are we below the sandbox editor?</span>
+<span id="L144" class="LineNr">144 </span>  click-sandbox-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L190'>click-on-sandbox-area?</a> click-row, click-column, env
+<span id="L145" class="LineNr">145 </span>  <span class="muControl">return-unless</span> click-sandbox-area?, <span class="Constant">0/false</span>
+<span id="L146" class="LineNr">146 </span>  <span class="Comment"># narrower, is the click in the columns spanning the 'copy' button?</span>
+<span id="L147" class="LineNr">147 </span>  first-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L148" class="LineNr">148 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
+<span id="L149" class="LineNr">149 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
+<span id="L150" class="LineNr">150 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
+<span id="L151" class="LineNr">151 </span>  _, _, copy-button-left:num, copy-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L344'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
+<span id="L152" class="LineNr">152 </span>  copy-button-vertical-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L211'>within-range?</a> click-column, copy-button-left, copy-button-right
+<span id="L153" class="LineNr">153 </span>  <span class="muControl">return-unless</span> copy-button-vertical-area?, <span class="Constant">0/false</span>
+<span id="L154" class="LineNr">154 </span>  <span class="Comment"># finally, is sandbox editor empty?</span>
+<span id="L155" class="LineNr">155 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L156" class="LineNr">156 </span>  result <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L203'>empty-editor?</a> current-sandbox
+<span id="L157" class="LineNr">157 </span>]
+<span id="L158" class="LineNr">158 </span>
+<span id="L159" class="LineNr">159 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L159'>try-copy-sandbox</a> click-row:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>clicked-on-copy-button?:bool, env:&amp;:environment [
+<span id="L160" class="LineNr">160 </span>  <span class="Constant">local-scope</span>
+<span id="L161" class="LineNr">161 </span>  <span class="Constant">load-ingredients</span>
+<span id="L162" class="LineNr">162 </span>  <span class="Comment"># identify the sandbox to copy, if the click was actually on the 'copy' button</span>
+<span id="L163" class="LineNr">163 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L175'>find-sandbox</a> env, click-row
+<span id="L164" class="LineNr">164 </span>  <span class="muControl">return-unless</span> sandbox, <span class="Constant">0/false</span>
+<span id="L165" class="LineNr">165 </span>  clicked-on-copy-button? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
+<span id="L166" class="LineNr">166 </span>  text:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
+<span id="L167" class="LineNr">167 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L168" class="LineNr">168 </span>  current-sandbox <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L73'>insert-text</a> current-sandbox, text
+<span id="L169" class="LineNr">169 </span>  <span class="Comment"># reset scroll</span>
+<span id="L170" class="LineNr">170 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>,<span class="Constant"> -1</span>
+<span id="L171" class="LineNr">171 </span>  <span class="Comment"># position cursor in sandbox editor</span>
+<span id="L172" class="LineNr">172 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, <span class="Constant">1/true</span>
+<span id="L173" class="LineNr">173 </span>]
+<span id="L174" class="LineNr">174 </span>
+<span id="L175" class="LineNr">175 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L175'>find-sandbox</a> env:&amp;:environment, click-row:num<span class="muRecipe"> -&gt; </span>result:&amp;:sandbox [
+<span id="L176" class="LineNr">176 </span>  <span class="Constant">local-scope</span>
+<span id="L177" class="LineNr">177 </span>  <span class="Constant">load-ingredients</span>
+<span id="L178" class="LineNr">178 </span>  curr-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L179" class="LineNr">179 </span>  <span class="Delimiter">{</span>
+<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr-sandbox
+<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> start:num <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal click-row, start
+<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> <span class="muControl">return-if</span> found?, curr-sandbox
+<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> curr-sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L186" class="LineNr">186 </span>  <span class="Delimiter">}</span>
+<span id="L187" class="LineNr">187 </span>  <span class="muControl">return</span> <span class="Constant">0/not-found</span>
+<span id="L188" class="LineNr">188 </span>]
+<span id="L189" class="LineNr">189 </span>
+<span id="L190" class="LineNr">190 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L190'>click-on-sandbox-area?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
+<span id="L191" class="LineNr">191 </span>  <span class="Constant">local-scope</span>
+<span id="L192" class="LineNr">192 </span>  <span class="Constant">load-ingredients</span>
+<span id="L193" class="LineNr">193 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L194" class="LineNr">194 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
+<span id="L195" class="LineNr">195 </span>  on-sandbox-side?:bool <span class="Special">&lt;-</span> greater-or-equal click-column, sandbox-left-margin
+<span id="L196" class="LineNr">196 </span>  <span class="muControl">return-unless</span> on-sandbox-side?, <span class="Constant">0/false</span>
+<span id="L197" class="LineNr">197 </span>  first-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L198" class="LineNr">198 </span>  <span class="muControl">return-unless</span> first-sandbox, <span class="Constant">0/false</span>
+<span id="L199" class="LineNr">199 </span>  first-sandbox-begins:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+<span id="L200" class="LineNr">200 </span>  result <span class="Special">&lt;-</span> greater-or-equal click-row, first-sandbox-begins
+<span id="L201" class="LineNr">201 </span>]
+<span id="L202" class="LineNr">202 </span>
+<span id="L203" class="LineNr">203 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L203'>empty-editor?</a> editor:&amp;:editor<span class="muRecipe"> -&gt; </span>result:bool [
+<span id="L204" class="LineNr">204 </span>  <span class="Constant">local-scope</span>
+<span id="L205" class="LineNr">205 </span>  <span class="Constant">load-ingredients</span>
+<span id="L206" class="LineNr">206 </span>  head:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
+<span id="L207" class="LineNr">207 </span>  first:&amp;:<a href='../065duplex_list.mu.html#L3'>duplex-list</a>:char <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> head
+<span id="L208" class="LineNr">208 </span>  result <span class="Special">&lt;-</span> not first
+<span id="L209" class="LineNr">209 </span>]
+<span id="L210" class="LineNr">210 </span>
+<span id="L211" class="LineNr">211 </span><span class="muRecipe">def</span> <a href='006-sandbox-copy.mu.html#L211'>within-range?</a> x:num, low:num, high:num<span class="muRecipe"> -&gt; </span>result:bool [
+<span id="L212" class="LineNr">212 </span>  <span class="Constant">local-scope</span>
+<span id="L213" class="LineNr">213 </span>  <span class="Constant">load-ingredients</span>
+<span id="L214" class="LineNr">214 </span>  not-too-far-left?:bool <span class="Special">&lt;-</span> greater-or-equal x, low
+<span id="L215" class="LineNr">215 </span>  not-too-far-right?:bool <span class="Special">&lt;-</span> lesser-or-equal x, high
+<span id="L216" class="LineNr">216 </span>  result <span class="Special">&lt;-</span> and not-too-far-left? not-too-far-right?
+<span id="L217" class="LineNr">217 </span>]
+<span id="L218" class="LineNr">218 </span>
+<span id="L219" class="LineNr">219 </span><span class="muScenario">scenario</span> copy-fails-if-sandbox-editor-not-empty [
+<span id="L220" class="LineNr">220 </span>  <span class="Constant">local-scope</span>
+<span id="L221" class="LineNr">221 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L222" class="LineNr">222 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L223" class="LineNr">223 </span>  <span class="Comment"># empty recipes</span>
+<span id="L224" class="LineNr">224 </span>  assume-resources [
+<span id="L225" class="LineNr">225 </span>  ]
+<span id="L226" class="LineNr">226 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 1, 1]</span>  <span class="Comment"># contents of sandbox editor</span>
+<span id="L227" class="LineNr">227 </span>  <span class="Comment"># run it</span>
+<span id="L228" class="LineNr">228 </span>  assume-console [
+<span id="L229" class="LineNr">229 </span>  <span class="Conceal">¦</span> press F4
+<span id="L230" class="LineNr">230 </span>  ]
+<span id="L231" class="LineNr">231 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L232" class="LineNr">232 </span>  screen-should-contain [
+<span id="L233" class="LineNr">233 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L234" class="LineNr">234 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L235" class="LineNr">235 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L236" class="LineNr">236 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L238" class="LineNr">238 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L239" class="LineNr">239 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L240" class="LineNr">240 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L241" class="LineNr">241 </span>  ]
+<span id="L242" class="LineNr">242 </span>  <span class="Comment"># type something into the sandbox editor, then click on the 'copy' button</span>
+<span id="L243" class="LineNr">243 </span>  assume-console [
+<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 70</span>  <span class="Comment"># put cursor in sandbox editor</span>
+<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span> type <span class="Constant">[0]</span>  <span class="Comment"># type something</span>
+<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 70</span>  <span class="Comment"># click 'copy' button</span>
+<span id="L247" class="LineNr">247 </span>  ]
+<span id="L248" class="LineNr">248 </span>  run [
+<span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L250" class="LineNr">250 </span>  ]
+<span id="L251" class="LineNr">251 </span>  <span class="Comment"># copy doesn't happen</span>
+<span id="L252" class="LineNr">252 </span>  screen-should-contain [
+<span id="L253" class="LineNr">253 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L254" class="LineNr">254 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0                                                .</span>
+<span id="L255" class="LineNr">255 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L257" class="LineNr">257 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L258" class="LineNr">258 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L259" class="LineNr">259 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L260" class="LineNr">260 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L261" class="LineNr">261 </span>  ]
+<span id="L262" class="LineNr">262 </span>  <span class="Comment"># cursor should be in the right place</span>
+<span id="L263" class="LineNr">263 </span>  assume-console [
+<span id="L264" class="LineNr">264 </span>  <span class="Conceal">¦</span> type <span class="Constant">[1]</span>
+<span id="L265" class="LineNr">265 </span>  ]
+<span id="L266" class="LineNr">266 </span>  run [
+<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L268" class="LineNr">268 </span>  ]
+<span id="L269" class="LineNr">269 </span>  screen-should-contain [
+<span id="L270" class="LineNr">270 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎01                                               .</span>
+<span id="L272" class="LineNr">272 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L273" class="LineNr">273 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L274" class="LineNr">274 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L275" class="LineNr">275 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L276" class="LineNr">276 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L278" class="LineNr">278 </span>  ]
+<span id="L279" class="LineNr">279 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/007-sandbox-delete.mu.html b/html/edit/007-sandbox-delete.mu.html
index 327563c0..4d297d8b 100644
--- a/html/edit/007-sandbox-delete.mu.html
+++ b/html/edit/007-sandbox-delete.mu.html
@@ -127,280 +127,282 @@ if ('onhashchange' in window) {
 <span id="L65" class="LineNr"> 65 </span>  ]
 <span id="L66" class="LineNr"> 66 </span>]
 <span id="L67" class="LineNr"> 67 </span>
-<span id="L68" class="LineNr"> 68 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L76'>&lt;global-touch&gt;</a></span> [
+<span id="L68" class="LineNr"> 68 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L80'>&lt;global-touch&gt;</a></span> [
 <span id="L69" class="LineNr"> 69 </span>  <span class="Comment"># support 'delete' button</span>
 <span id="L70" class="LineNr"> 70 </span>  <span class="Delimiter">{</span>
-<span id="L71" class="LineNr"> 71 </span>  <span class="Conceal">¦</span> delete?:bool <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L82'>should-attempt-delete?</a> click-row, click-column, env
+<span id="L71" class="LineNr"> 71 </span>  <span class="Conceal">¦</span> delete?:bool <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L84'>should-attempt-delete?</a> click-row, click-column, env
 <span id="L72" class="LineNr"> 72 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> delete?
-<span id="L73" class="LineNr"> 73 </span>  <span class="Conceal">¦</span> delete?, env <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L97'>try-delete-sandbox</a> click-row, env
+<span id="L73" class="LineNr"> 73 </span>  <span class="Conceal">¦</span> delete?, env <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L99'>try-delete-sandbox</a> click-row, env
 <span id="L74" class="LineNr"> 74 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> delete?
-<span id="L75" class="LineNr"> 75 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L76" class="LineNr"> 76 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L77" class="LineNr"> 77 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L78" class="LineNr"> 78 </span>  <span class="Delimiter">}</span>
-<span id="L79" class="LineNr"> 79 </span>]
-<span id="L80" class="LineNr"> 80 </span>
-<span id="L81" class="LineNr"> 81 </span><span class="Comment"># some preconditions for attempting to delete a sandbox</span>
-<span id="L82" class="LineNr"> 82 </span><span class="muRecipe">def</span> <a href='007-sandbox-delete.mu.html#L82'>should-attempt-delete?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
-<span id="L83" class="LineNr"> 83 </span>  <span class="Constant">local-scope</span>
-<span id="L84" class="LineNr"> 84 </span>  <span class="Constant">load-ingredients</span>
-<span id="L85" class="LineNr"> 85 </span>  <span class="Comment"># are we below the sandbox editor?</span>
-<span id="L86" class="LineNr"> 86 </span>  click-sandbox-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L188'>click-on-sandbox-area?</a> click-row, click-column, env
-<span id="L87" class="LineNr"> 87 </span>  <span class="muControl">return-unless</span> click-sandbox-area?, <span class="Constant">0/false</span>
-<span id="L88" class="LineNr"> 88 </span>  <span class="Comment"># narrower, is the click in the columns spanning the 'copy' button?</span>
-<span id="L89" class="LineNr"> 89 </span>  first-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L90" class="LineNr"> 90 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
-<span id="L91" class="LineNr"> 91 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
-<span id="L92" class="LineNr"> 92 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
-<span id="L93" class="LineNr"> 93 </span>  _, _, _, _, delete-button-left:num <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L344'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
-<span id="L94" class="LineNr"> 94 </span>  result <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L209'>within-range?</a> click-column, delete-button-left, sandbox-right-margin
-<span id="L95" class="LineNr"> 95 </span>]
-<span id="L96" class="LineNr"> 96 </span>
-<span id="L97" class="LineNr"> 97 </span><span class="muRecipe">def</span> <a href='007-sandbox-delete.mu.html#L97'>try-delete-sandbox</a> click-row:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>clicked-on-delete-button?:bool, env:&amp;:environment [
-<span id="L98" class="LineNr"> 98 </span>  <span class="Constant">local-scope</span>
-<span id="L99" class="LineNr"> 99 </span>  <span class="Constant">load-ingredients</span>
-<span id="L100" class="LineNr">100 </span>  <span class="Comment"># identify the sandbox to delete, if the click was actually on the 'delete' button</span>
-<span id="L101" class="LineNr">101 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L173'>find-sandbox</a> env, click-row
-<span id="L102" class="LineNr">102 </span>  <span class="muControl">return-unless</span> sandbox, <span class="Constant">0/false</span>
-<span id="L103" class="LineNr">103 </span>  clicked-on-delete-button? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-<span id="L104" class="LineNr">104 </span>  env <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L107'>delete-sandbox</a> env, sandbox
-<span id="L105" class="LineNr">105 </span>]
-<span id="L106" class="LineNr">106 </span>
-<span id="L107" class="LineNr">107 </span><span class="muRecipe">def</span> <a href='007-sandbox-delete.mu.html#L107'>delete-sandbox</a> env:&amp;:environment, sandbox:&amp;:sandbox<span class="muRecipe"> -&gt; </span>env:&amp;:environment [
-<span id="L108" class="LineNr">108 </span>  <span class="Constant">local-scope</span>
-<span id="L109" class="LineNr">109 </span>  <span class="Constant">load-ingredients</span>
-<span id="L110" class="LineNr">110 </span>  curr-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L111" class="LineNr">111 </span>  first-sandbox?:bool <span class="Special">&lt;-</span> equal curr-sandbox, sandbox
-<span id="L112" class="LineNr">112 </span>  <span class="Delimiter">{</span>
-<span id="L113" class="LineNr">113 </span>  <span class="Conceal">¦</span> <span class="Comment"># first sandbox? pop</span>
-<span id="L114" class="LineNr">114 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> first-sandbox?
-<span id="L115" class="LineNr">115 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L116" class="LineNr">116 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox:offset</span>, next-sandbox
-<span id="L117" class="LineNr">117 </span>  <span class="Delimiter">}</span>
-<span id="L118" class="LineNr">118 </span>  <span class="Delimiter">{</span>
-<span id="L119" class="LineNr">119 </span>  <span class="Conceal">¦</span> <span class="Comment"># not first sandbox?</span>
-<span id="L120" class="LineNr">120 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> first-sandbox?
-<span id="L121" class="LineNr">121 </span>  <span class="Conceal">¦</span> prev-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> copy curr-sandbox
-<span id="L122" class="LineNr">122 </span>  <span class="Conceal">¦</span> curr-sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L123" class="LineNr">123 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L124" class="LineNr">124 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> assert curr-sandbox, <span class="Constant">[sandbox not found! something is wrong.]</span>
-<span id="L125" class="LineNr">125 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal curr-sandbox, sandbox
-<span id="L126" class="LineNr">126 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
-<span id="L127" class="LineNr">127 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> prev-sandbox <span class="Special">&lt;-</span> copy curr-sandbox
-<span id="L128" class="LineNr">128 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr-sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L130" class="LineNr">130 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> <span class="Comment"># snip sandbox out of its list</span>
-<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> *prev-sandbox <span class="Special">&lt;-</span> put *prev-sandbox, <span class="Constant">next-sandbox:offset</span>, next-sandbox
-<span id="L134" class="LineNr">134 </span>  <span class="Delimiter">}</span>
-<span id="L135" class="LineNr">135 </span>  <span class="Comment"># update sandbox count</span>
-<span id="L136" class="LineNr">136 </span>  sandbox-count:num <span class="Special">&lt;-</span> get *env, <span class="Constant">number-of-sandboxes:offset</span>
-<span id="L137" class="LineNr">137 </span>  sandbox-count <span class="Special">&lt;-</span> subtract sandbox-count,<span class="Constant"> 1</span>
-<span id="L138" class="LineNr">138 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">number-of-sandboxes:offset</span>, sandbox-count
-<span id="L139" class="LineNr">139 </span>  <span class="Comment"># reset scroll if deleted sandbox was last</span>
-<span id="L140" class="LineNr">140 </span>  <span class="Delimiter">{</span>
-<span id="L141" class="LineNr">141 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> next-sandbox
-<span id="L142" class="LineNr">142 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
-<span id="L143" class="LineNr">143 </span>  <span class="Conceal">¦</span> reset-scroll?:bool <span class="Special">&lt;-</span> equal render-from, sandbox-count
-<span id="L144" class="LineNr">144 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> reset-scroll?
-<span id="L145" class="LineNr">145 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>,<span class="Constant"> -1</span>
-<span id="L146" class="LineNr">146 </span>  <span class="Delimiter">}</span>
-<span id="L147" class="LineNr">147 </span>]
-<span id="L148" class="LineNr">148 </span>
-<span id="L149" class="LineNr">149 </span><span class="muScenario">scenario</span> deleting-sandbox-after-scroll [
-<span id="L150" class="LineNr">150 </span>  <span class="Constant">local-scope</span>
-<span id="L151" class="LineNr">151 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L152" class="LineNr">152 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L153" class="LineNr">153 </span>  <span class="Comment"># initialize environment</span>
-<span id="L154" class="LineNr">154 </span>  assume-resources [
-<span id="L155" class="LineNr">155 </span>  ]
-<span id="L156" class="LineNr">156 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L157" class="LineNr">157 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L158" class="LineNr">158 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
-<span id="L159" class="LineNr">159 </span>  assume-console [
-<span id="L160" class="LineNr">160 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L161" class="LineNr">161 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L162" class="LineNr">162 </span>  <span class="Conceal">¦</span> press F4
-<span id="L163" class="LineNr">163 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L75" class="LineNr"> 75 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L76" class="LineNr"> 76 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L77" class="LineNr"> 77 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L78" class="LineNr"> 78 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L79" class="LineNr"> 79 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L80" class="LineNr"> 80 </span>  <span class="Delimiter">}</span>
+<span id="L81" class="LineNr"> 81 </span>]
+<span id="L82" class="LineNr"> 82 </span>
+<span id="L83" class="LineNr"> 83 </span><span class="Comment"># some preconditions for attempting to delete a sandbox</span>
+<span id="L84" class="LineNr"> 84 </span><span class="muRecipe">def</span> <a href='007-sandbox-delete.mu.html#L84'>should-attempt-delete?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
+<span id="L85" class="LineNr"> 85 </span>  <span class="Constant">local-scope</span>
+<span id="L86" class="LineNr"> 86 </span>  <span class="Constant">load-ingredients</span>
+<span id="L87" class="LineNr"> 87 </span>  <span class="Comment"># are we below the sandbox editor?</span>
+<span id="L88" class="LineNr"> 88 </span>  click-sandbox-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L190'>click-on-sandbox-area?</a> click-row, click-column, env
+<span id="L89" class="LineNr"> 89 </span>  <span class="muControl">return-unless</span> click-sandbox-area?, <span class="Constant">0/false</span>
+<span id="L90" class="LineNr"> 90 </span>  <span class="Comment"># narrower, is the click in the columns spanning the 'copy' button?</span>
+<span id="L91" class="LineNr"> 91 </span>  first-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L92" class="LineNr"> 92 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
+<span id="L93" class="LineNr"> 93 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
+<span id="L94" class="LineNr"> 94 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
+<span id="L95" class="LineNr"> 95 </span>  _, _, _, _, delete-button-left:num <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L344'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
+<span id="L96" class="LineNr"> 96 </span>  result <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L211'>within-range?</a> click-column, delete-button-left, sandbox-right-margin
+<span id="L97" class="LineNr"> 97 </span>]
+<span id="L98" class="LineNr"> 98 </span>
+<span id="L99" class="LineNr"> 99 </span><span class="muRecipe">def</span> <a href='007-sandbox-delete.mu.html#L99'>try-delete-sandbox</a> click-row:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>clicked-on-delete-button?:bool, env:&amp;:environment [
+<span id="L100" class="LineNr">100 </span>  <span class="Constant">local-scope</span>
+<span id="L101" class="LineNr">101 </span>  <span class="Constant">load-ingredients</span>
+<span id="L102" class="LineNr">102 </span>  <span class="Comment"># identify the sandbox to delete, if the click was actually on the 'delete' button</span>
+<span id="L103" class="LineNr">103 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L175'>find-sandbox</a> env, click-row
+<span id="L104" class="LineNr">104 </span>  <span class="muControl">return-unless</span> sandbox, <span class="Constant">0/false</span>
+<span id="L105" class="LineNr">105 </span>  clicked-on-delete-button? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
+<span id="L106" class="LineNr">106 </span>  env <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L109'>delete-sandbox</a> env, sandbox
+<span id="L107" class="LineNr">107 </span>]
+<span id="L108" class="LineNr">108 </span>
+<span id="L109" class="LineNr">109 </span><span class="muRecipe">def</span> <a href='007-sandbox-delete.mu.html#L109'>delete-sandbox</a> env:&amp;:environment, sandbox:&amp;:sandbox<span class="muRecipe"> -&gt; </span>env:&amp;:environment [
+<span id="L110" class="LineNr">110 </span>  <span class="Constant">local-scope</span>
+<span id="L111" class="LineNr">111 </span>  <span class="Constant">load-ingredients</span>
+<span id="L112" class="LineNr">112 </span>  curr-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L113" class="LineNr">113 </span>  first-sandbox?:bool <span class="Special">&lt;-</span> equal curr-sandbox, sandbox
+<span id="L114" class="LineNr">114 </span>  <span class="Delimiter">{</span>
+<span id="L115" class="LineNr">115 </span>  <span class="Conceal">¦</span> <span class="Comment"># first sandbox? pop</span>
+<span id="L116" class="LineNr">116 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> first-sandbox?
+<span id="L117" class="LineNr">117 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L118" class="LineNr">118 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox:offset</span>, next-sandbox
+<span id="L119" class="LineNr">119 </span>  <span class="Delimiter">}</span>
+<span id="L120" class="LineNr">120 </span>  <span class="Delimiter">{</span>
+<span id="L121" class="LineNr">121 </span>  <span class="Conceal">¦</span> <span class="Comment"># not first sandbox?</span>
+<span id="L122" class="LineNr">122 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> first-sandbox?
+<span id="L123" class="LineNr">123 </span>  <span class="Conceal">¦</span> prev-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> copy curr-sandbox
+<span id="L124" class="LineNr">124 </span>  <span class="Conceal">¦</span> curr-sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L125" class="LineNr">125 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L126" class="LineNr">126 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> assert curr-sandbox, <span class="Constant">[sandbox not found! something is wrong.]</span>
+<span id="L127" class="LineNr">127 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal curr-sandbox, sandbox
+<span id="L128" class="LineNr">128 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
+<span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> prev-sandbox <span class="Special">&lt;-</span> copy curr-sandbox
+<span id="L130" class="LineNr">130 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr-sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> <span class="Comment"># snip sandbox out of its list</span>
+<span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *curr-sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L135" class="LineNr">135 </span>  <span class="Conceal">¦</span> *prev-sandbox <span class="Special">&lt;-</span> put *prev-sandbox, <span class="Constant">next-sandbox:offset</span>, next-sandbox
+<span id="L136" class="LineNr">136 </span>  <span class="Delimiter">}</span>
+<span id="L137" class="LineNr">137 </span>  <span class="Comment"># update sandbox count</span>
+<span id="L138" class="LineNr">138 </span>  sandbox-count:num <span class="Special">&lt;-</span> get *env, <span class="Constant">number-of-sandboxes:offset</span>
+<span id="L139" class="LineNr">139 </span>  sandbox-count <span class="Special">&lt;-</span> subtract sandbox-count,<span class="Constant"> 1</span>
+<span id="L140" class="LineNr">140 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">number-of-sandboxes:offset</span>, sandbox-count
+<span id="L141" class="LineNr">141 </span>  <span class="Comment"># reset scroll if deleted sandbox was last</span>
+<span id="L142" class="LineNr">142 </span>  <span class="Delimiter">{</span>
+<span id="L143" class="LineNr">143 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> next-sandbox
+<span id="L144" class="LineNr">144 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
+<span id="L145" class="LineNr">145 </span>  <span class="Conceal">¦</span> reset-scroll?:bool <span class="Special">&lt;-</span> equal render-from, sandbox-count
+<span id="L146" class="LineNr">146 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> reset-scroll?
+<span id="L147" class="LineNr">147 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>,<span class="Constant"> -1</span>
+<span id="L148" class="LineNr">148 </span>  <span class="Delimiter">}</span>
+<span id="L149" class="LineNr">149 </span>]
+<span id="L150" class="LineNr">150 </span>
+<span id="L151" class="LineNr">151 </span><span class="muScenario">scenario</span> deleting-sandbox-after-scroll [
+<span id="L152" class="LineNr">152 </span>  <span class="Constant">local-scope</span>
+<span id="L153" class="LineNr">153 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L154" class="LineNr">154 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L155" class="LineNr">155 </span>  <span class="Comment"># initialize environment</span>
+<span id="L156" class="LineNr">156 </span>  assume-resources [
+<span id="L157" class="LineNr">157 </span>  ]
+<span id="L158" class="LineNr">158 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L159" class="LineNr">159 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L160" class="LineNr">160 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+<span id="L161" class="LineNr">161 </span>  assume-console [
+<span id="L162" class="LineNr">162 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L163" class="LineNr">163 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
 <span id="L164" class="LineNr">164 </span>  <span class="Conceal">¦</span> press F4
-<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L166" class="LineNr">166 </span>  ]
-<span id="L167" class="LineNr">167 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L168" class="LineNr">168 </span>  screen-should-contain [
-<span id="L169" class="LineNr">169 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L170" class="LineNr">170 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L175" class="LineNr">175 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L176" class="LineNr">176 </span>  ]
-<span id="L177" class="LineNr">177 </span>  <span class="Comment"># delete the second sandbox</span>
-<span id="L178" class="LineNr">178 </span>  assume-console [
-<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 6</span>,<span class="Constant"> 99</span>
-<span id="L180" class="LineNr">180 </span>  ]
-<span id="L181" class="LineNr">181 </span>  run [
-<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L183" class="LineNr">183 </span>  ]
-<span id="L184" class="LineNr">184 </span>  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
-<span id="L185" class="LineNr">185 </span>  screen-should-contain [
-<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L193" class="LineNr">193 </span>  ]
-<span id="L194" class="LineNr">194 </span>]
-<span id="L195" class="LineNr">195 </span>
-<span id="L196" class="LineNr">196 </span><span class="muScenario">scenario</span> deleting-top-sandbox-after-scroll [
-<span id="L197" class="LineNr">197 </span>  <span class="Constant">local-scope</span>
-<span id="L198" class="LineNr">198 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L199" class="LineNr">199 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L200" class="LineNr">200 </span>  <span class="Comment"># initialize environment</span>
-<span id="L201" class="LineNr">201 </span>  assume-resources [
-<span id="L202" class="LineNr">202 </span>  ]
-<span id="L203" class="LineNr">203 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L204" class="LineNr">204 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L205" class="LineNr">205 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
-<span id="L206" class="LineNr">206 </span>  assume-console [
-<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L209" class="LineNr">209 </span>  <span class="Conceal">¦</span> press F4
-<span id="L210" class="LineNr">210 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L166" class="LineNr">166 </span>  <span class="Conceal">¦</span> press F4
+<span id="L167" class="LineNr">167 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L168" class="LineNr">168 </span>  ]
+<span id="L169" class="LineNr">169 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L170" class="LineNr">170 </span>  screen-should-contain [
+<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L175" class="LineNr">175 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L178" class="LineNr">178 </span>  ]
+<span id="L179" class="LineNr">179 </span>  <span class="Comment"># delete the second sandbox</span>
+<span id="L180" class="LineNr">180 </span>  assume-console [
+<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 6</span>,<span class="Constant"> 99</span>
+<span id="L182" class="LineNr">182 </span>  ]
+<span id="L183" class="LineNr">183 </span>  run [
+<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L185" class="LineNr">185 </span>  ]
+<span id="L186" class="LineNr">186 </span>  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
+<span id="L187" class="LineNr">187 </span>  screen-should-contain [
+<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L195" class="LineNr">195 </span>  ]
+<span id="L196" class="LineNr">196 </span>]
+<span id="L197" class="LineNr">197 </span>
+<span id="L198" class="LineNr">198 </span><span class="muScenario">scenario</span> deleting-top-sandbox-after-scroll [
+<span id="L199" class="LineNr">199 </span>  <span class="Constant">local-scope</span>
+<span id="L200" class="LineNr">200 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L201" class="LineNr">201 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L202" class="LineNr">202 </span>  <span class="Comment"># initialize environment</span>
+<span id="L203" class="LineNr">203 </span>  assume-resources [
+<span id="L204" class="LineNr">204 </span>  ]
+<span id="L205" class="LineNr">205 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L206" class="LineNr">206 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L207" class="LineNr">207 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+<span id="L208" class="LineNr">208 </span>  assume-console [
+<span id="L209" class="LineNr">209 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L210" class="LineNr">210 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
 <span id="L211" class="LineNr">211 </span>  <span class="Conceal">¦</span> press F4
-<span id="L212" class="LineNr">212 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L213" class="LineNr">213 </span>  ]
-<span id="L214" class="LineNr">214 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L215" class="LineNr">215 </span>  screen-should-contain [
-<span id="L216" class="LineNr">216 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L217" class="LineNr">217 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L218" class="LineNr">218 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L220" class="LineNr">220 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L221" class="LineNr">221 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L222" class="LineNr">222 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L223" class="LineNr">223 </span>  ]
-<span id="L224" class="LineNr">224 </span>  <span class="Comment"># delete the second sandbox</span>
-<span id="L225" class="LineNr">225 </span>  assume-console [
-<span id="L226" class="LineNr">226 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 99</span>
-<span id="L227" class="LineNr">227 </span>  ]
-<span id="L228" class="LineNr">228 </span>  run [
-<span id="L229" class="LineNr">229 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L230" class="LineNr">230 </span>  ]
-<span id="L231" class="LineNr">231 </span>  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
-<span id="L232" class="LineNr">232 </span>  screen-should-contain [
-<span id="L233" class="LineNr">233 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L234" class="LineNr">234 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L235" class="LineNr">235 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L236" class="LineNr">236 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L238" class="LineNr">238 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L239" class="LineNr">239 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L240" class="LineNr">240 </span>  ]
-<span id="L241" class="LineNr">241 </span>]
-<span id="L242" class="LineNr">242 </span>
-<span id="L243" class="LineNr">243 </span><span class="muScenario">scenario</span> deleting-final-sandbox-after-scroll [
-<span id="L244" class="LineNr">244 </span>  <span class="Constant">local-scope</span>
-<span id="L245" class="LineNr">245 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L246" class="LineNr">246 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L247" class="LineNr">247 </span>  <span class="Comment"># initialize environment</span>
-<span id="L248" class="LineNr">248 </span>  assume-resources [
-<span id="L249" class="LineNr">249 </span>  ]
-<span id="L250" class="LineNr">250 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L251" class="LineNr">251 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L252" class="LineNr">252 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
-<span id="L253" class="LineNr">253 </span>  assume-console [
-<span id="L254" class="LineNr">254 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L255" class="LineNr">255 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span> press F4
-<span id="L257" class="LineNr">257 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L212" class="LineNr">212 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L213" class="LineNr">213 </span>  <span class="Conceal">¦</span> press F4
+<span id="L214" class="LineNr">214 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L215" class="LineNr">215 </span>  ]
+<span id="L216" class="LineNr">216 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L217" class="LineNr">217 </span>  screen-should-contain [
+<span id="L218" class="LineNr">218 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L220" class="LineNr">220 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L221" class="LineNr">221 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L222" class="LineNr">222 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L223" class="LineNr">223 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L224" class="LineNr">224 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L225" class="LineNr">225 </span>  ]
+<span id="L226" class="LineNr">226 </span>  <span class="Comment"># delete the second sandbox</span>
+<span id="L227" class="LineNr">227 </span>  assume-console [
+<span id="L228" class="LineNr">228 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 99</span>
+<span id="L229" class="LineNr">229 </span>  ]
+<span id="L230" class="LineNr">230 </span>  run [
+<span id="L231" class="LineNr">231 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L232" class="LineNr">232 </span>  ]
+<span id="L233" class="LineNr">233 </span>  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
+<span id="L234" class="LineNr">234 </span>  screen-should-contain [
+<span id="L235" class="LineNr">235 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L236" class="LineNr">236 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L238" class="LineNr">238 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L239" class="LineNr">239 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L240" class="LineNr">240 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L241" class="LineNr">241 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L242" class="LineNr">242 </span>  ]
+<span id="L243" class="LineNr">243 </span>]
+<span id="L244" class="LineNr">244 </span>
+<span id="L245" class="LineNr">245 </span><span class="muScenario">scenario</span> deleting-final-sandbox-after-scroll [
+<span id="L246" class="LineNr">246 </span>  <span class="Constant">local-scope</span>
+<span id="L247" class="LineNr">247 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L248" class="LineNr">248 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L249" class="LineNr">249 </span>  <span class="Comment"># initialize environment</span>
+<span id="L250" class="LineNr">250 </span>  assume-resources [
+<span id="L251" class="LineNr">251 </span>  ]
+<span id="L252" class="LineNr">252 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L253" class="LineNr">253 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L254" class="LineNr">254 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+<span id="L255" class="LineNr">255 </span>  assume-console [
+<span id="L256" class="LineNr">256 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L257" class="LineNr">257 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
 <span id="L258" class="LineNr">258 </span>  <span class="Conceal">¦</span> press F4
-<span id="L259" class="LineNr">259 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L260" class="LineNr">260 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L261" class="LineNr">261 </span>  ]
-<span id="L262" class="LineNr">262 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L263" class="LineNr">263 </span>  screen-should-contain [
-<span id="L264" class="LineNr">264 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L266" class="LineNr">266 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
-<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L268" class="LineNr">268 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L269" class="LineNr">269 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L270" class="LineNr">270 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L271" class="LineNr">271 </span>  ]
-<span id="L272" class="LineNr">272 </span>  <span class="Comment"># delete the second sandbox</span>
-<span id="L273" class="LineNr">273 </span>  assume-console [
-<span id="L274" class="LineNr">274 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 99</span>
-<span id="L275" class="LineNr">275 </span>  ]
-<span id="L276" class="LineNr">276 </span>  run [
-<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L278" class="LineNr">278 </span>  ]
-<span id="L279" class="LineNr">279 </span>  <span class="Comment"># implicitly scroll up to first sandbox</span>
-<span id="L280" class="LineNr">280 </span>  screen-should-contain [
-<span id="L281" class="LineNr">281 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L282" class="LineNr">282 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L283" class="LineNr">283 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L284" class="LineNr">284 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L285" class="LineNr">285 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L286" class="LineNr">286 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L287" class="LineNr">287 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L288" class="LineNr">288 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L289" class="LineNr">289 </span>  ]
-<span id="L290" class="LineNr">290 </span>]
-<span id="L291" class="LineNr">291 </span>
-<span id="L292" class="LineNr">292 </span><span class="muScenario">scenario</span> deleting-updates-sandbox-count [
-<span id="L293" class="LineNr">293 </span>  <span class="Constant">local-scope</span>
-<span id="L294" class="LineNr">294 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L295" class="LineNr">295 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L296" class="LineNr">296 </span>  <span class="Comment"># initialize environment</span>
-<span id="L297" class="LineNr">297 </span>  assume-resources [
-<span id="L298" class="LineNr">298 </span>  ]
-<span id="L299" class="LineNr">299 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L300" class="LineNr">300 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L301" class="LineNr">301 </span>  <span class="Comment"># create 2 sandboxes</span>
-<span id="L302" class="LineNr">302 </span>  assume-console [
-<span id="L303" class="LineNr">303 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L304" class="LineNr">304 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L305" class="LineNr">305 </span>  <span class="Conceal">¦</span> press F4
-<span id="L306" class="LineNr">306 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L259" class="LineNr">259 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L260" class="LineNr">260 </span>  <span class="Conceal">¦</span> press F4
+<span id="L261" class="LineNr">261 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L262" class="LineNr">262 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L263" class="LineNr">263 </span>  ]
+<span id="L264" class="LineNr">264 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L265" class="LineNr">265 </span>  screen-should-contain [
+<span id="L266" class="LineNr">266 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L268" class="LineNr">268 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
+<span id="L269" class="LineNr">269 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L270" class="LineNr">270 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L272" class="LineNr">272 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L273" class="LineNr">273 </span>  ]
+<span id="L274" class="LineNr">274 </span>  <span class="Comment"># delete the second sandbox</span>
+<span id="L275" class="LineNr">275 </span>  assume-console [
+<span id="L276" class="LineNr">276 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 99</span>
+<span id="L277" class="LineNr">277 </span>  ]
+<span id="L278" class="LineNr">278 </span>  run [
+<span id="L279" class="LineNr">279 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L280" class="LineNr">280 </span>  ]
+<span id="L281" class="LineNr">281 </span>  <span class="Comment"># implicitly scroll up to first sandbox</span>
+<span id="L282" class="LineNr">282 </span>  screen-should-contain [
+<span id="L283" class="LineNr">283 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L284" class="LineNr">284 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L285" class="LineNr">285 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L286" class="LineNr">286 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L287" class="LineNr">287 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L288" class="LineNr">288 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L289" class="LineNr">289 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L290" class="LineNr">290 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L291" class="LineNr">291 </span>  ]
+<span id="L292" class="LineNr">292 </span>]
+<span id="L293" class="LineNr">293 </span>
+<span id="L294" class="LineNr">294 </span><span class="muScenario">scenario</span> deleting-updates-sandbox-count [
+<span id="L295" class="LineNr">295 </span>  <span class="Constant">local-scope</span>
+<span id="L296" class="LineNr">296 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L297" class="LineNr">297 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L298" class="LineNr">298 </span>  <span class="Comment"># initialize environment</span>
+<span id="L299" class="LineNr">299 </span>  assume-resources [
+<span id="L300" class="LineNr">300 </span>  ]
+<span id="L301" class="LineNr">301 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L302" class="LineNr">302 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L303" class="LineNr">303 </span>  <span class="Comment"># create 2 sandboxes</span>
+<span id="L304" class="LineNr">304 </span>  assume-console [
+<span id="L305" class="LineNr">305 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L306" class="LineNr">306 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
 <span id="L307" class="LineNr">307 </span>  <span class="Conceal">¦</span> press F4
-<span id="L308" class="LineNr">308 </span>  ]
-<span id="L309" class="LineNr">309 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L310" class="LineNr">310 </span>  screen-should-contain [
-<span id="L311" class="LineNr">311 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L312" class="LineNr">312 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L313" class="LineNr">313 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L314" class="LineNr">314 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L315" class="LineNr">315 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L318" class="LineNr">318 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L320" class="LineNr">320 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L321" class="LineNr">321 </span>  ]
-<span id="L322" class="LineNr">322 </span>  <span class="Comment"># delete the second sandbox, then try to scroll down twice</span>
-<span id="L323" class="LineNr">323 </span>  assume-console [
-<span id="L324" class="LineNr">324 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 99</span>
-<span id="L325" class="LineNr">325 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L326" class="LineNr">326 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L327" class="LineNr">327 </span>  ]
-<span id="L328" class="LineNr">328 </span>  run [
-<span id="L329" class="LineNr">329 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L330" class="LineNr">330 </span>  ]
-<span id="L331" class="LineNr">331 </span>  <span class="Comment"># shouldn't go past last sandbox</span>
-<span id="L332" class="LineNr">332 </span>  screen-should-contain [
-<span id="L333" class="LineNr">333 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L334" class="LineNr">334 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L335" class="LineNr">335 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L336" class="LineNr">336 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L337" class="LineNr">337 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L338" class="LineNr">338 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L339" class="LineNr">339 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L340" class="LineNr">340 </span>  ]
-<span id="L341" class="LineNr">341 </span>]
+<span id="L308" class="LineNr">308 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L309" class="LineNr">309 </span>  <span class="Conceal">¦</span> press F4
+<span id="L310" class="LineNr">310 </span>  ]
+<span id="L311" class="LineNr">311 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L312" class="LineNr">312 </span>  screen-should-contain [
+<span id="L313" class="LineNr">313 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L314" class="LineNr">314 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L315" class="LineNr">315 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L318" class="LineNr">318 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L320" class="LineNr">320 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L321" class="LineNr">321 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L322" class="LineNr">322 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L323" class="LineNr">323 </span>  ]
+<span id="L324" class="LineNr">324 </span>  <span class="Comment"># delete the second sandbox, then try to scroll down twice</span>
+<span id="L325" class="LineNr">325 </span>  assume-console [
+<span id="L326" class="LineNr">326 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 99</span>
+<span id="L327" class="LineNr">327 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L328" class="LineNr">328 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L329" class="LineNr">329 </span>  ]
+<span id="L330" class="LineNr">330 </span>  run [
+<span id="L331" class="LineNr">331 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L332" class="LineNr">332 </span>  ]
+<span id="L333" class="LineNr">333 </span>  <span class="Comment"># shouldn't go past last sandbox</span>
+<span id="L334" class="LineNr">334 </span>  screen-should-contain [
+<span id="L335" class="LineNr">335 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L336" class="LineNr">336 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L337" class="LineNr">337 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L338" class="LineNr">338 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L339" class="LineNr">339 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L340" class="LineNr">340 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L341" class="LineNr">341 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L342" class="LineNr">342 </span>  ]
+<span id="L343" class="LineNr">343 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/008-sandbox-edit.mu.html b/html/edit/008-sandbox-edit.mu.html
index f1ea0ffb..29b9b889 100644
--- a/html/edit/008-sandbox-edit.mu.html
+++ b/html/edit/008-sandbox-edit.mu.html
@@ -166,222 +166,224 @@ if ('onhashchange' in window) {
 <span id="L104" class="LineNr">104 </span>  ]
 <span id="L105" class="LineNr">105 </span>]
 <span id="L106" class="LineNr">106 </span>
-<span id="L107" class="LineNr">107 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L76'>&lt;global-touch&gt;</a></span> [
+<span id="L107" class="LineNr">107 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L80'>&lt;global-touch&gt;</a></span> [
 <span id="L108" class="LineNr">108 </span>  <span class="Comment"># support 'edit' button</span>
 <span id="L109" class="LineNr">109 </span>  <span class="Delimiter">{</span>
-<span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</span> edit?:bool <span class="Special">&lt;-</span> <a href='008-sandbox-edit.mu.html#L121'>should-attempt-edit?</a> click-row, click-column, env
+<span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</span> edit?:bool <span class="Special">&lt;-</span> <a href='008-sandbox-edit.mu.html#L123'>should-attempt-edit?</a> click-row, click-column, env
 <span id="L111" class="LineNr">111 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> edit?
-<span id="L112" class="LineNr">112 </span>  <span class="Conceal">¦</span> edit?, env <span class="Special">&lt;-</span> <a href='008-sandbox-edit.mu.html#L140'>try-edit-sandbox</a> click-row, env
+<span id="L112" class="LineNr">112 </span>  <span class="Conceal">¦</span> edit?, env <span class="Special">&lt;-</span> <a href='008-sandbox-edit.mu.html#L142'>try-edit-sandbox</a> click-row, env
 <span id="L113" class="LineNr">113 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> edit?
-<span id="L114" class="LineNr">114 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L115" class="LineNr">115 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L116" class="LineNr">116 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L117" class="LineNr">117 </span>  <span class="Delimiter">}</span>
-<span id="L118" class="LineNr">118 </span>]
-<span id="L119" class="LineNr">119 </span>
-<span id="L120" class="LineNr">120 </span><span class="Comment"># some preconditions for attempting to edit a sandbox</span>
-<span id="L121" class="LineNr">121 </span><span class="muRecipe">def</span> <a href='008-sandbox-edit.mu.html#L121'>should-attempt-edit?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
-<span id="L122" class="LineNr">122 </span>  <span class="Constant">local-scope</span>
-<span id="L123" class="LineNr">123 </span>  <span class="Constant">load-ingredients</span>
-<span id="L124" class="LineNr">124 </span>  <span class="Comment"># are we below the sandbox editor?</span>
-<span id="L125" class="LineNr">125 </span>  click-sandbox-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L188'>click-on-sandbox-area?</a> click-row, click-column, env
-<span id="L126" class="LineNr">126 </span>  <span class="muControl">return-unless</span> click-sandbox-area?, <span class="Constant">0/false</span>
-<span id="L127" class="LineNr">127 </span>  <span class="Comment"># narrower, is the click in the columns spanning the 'edit' button?</span>
-<span id="L128" class="LineNr">128 </span>  first-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L129" class="LineNr">129 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
-<span id="L130" class="LineNr">130 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
-<span id="L131" class="LineNr">131 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
-<span id="L132" class="LineNr">132 </span>  edit-button-left:num, edit-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L344'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
-<span id="L133" class="LineNr">133 </span>  edit-button-vertical-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L209'>within-range?</a> click-column, edit-button-left, edit-button-right
-<span id="L134" class="LineNr">134 </span>  <span class="muControl">return-unless</span> edit-button-vertical-area?, <span class="Constant">0/false</span>
-<span id="L135" class="LineNr">135 </span>  <span class="Comment"># finally, is sandbox editor empty?</span>
-<span id="L136" class="LineNr">136 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L137" class="LineNr">137 </span>  result <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L201'>empty-editor?</a> current-sandbox
-<span id="L138" class="LineNr">138 </span>]
-<span id="L139" class="LineNr">139 </span>
-<span id="L140" class="LineNr">140 </span><span class="muRecipe">def</span> <a href='008-sandbox-edit.mu.html#L140'>try-edit-sandbox</a> click-row:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>clicked-on-edit-button?:bool, env:&amp;:environment [
-<span id="L141" class="LineNr">141 </span>  <span class="Constant">local-scope</span>
-<span id="L142" class="LineNr">142 </span>  <span class="Constant">load-ingredients</span>
-<span id="L143" class="LineNr">143 </span>  <span class="Comment"># identify the sandbox to edit, if the click was actually on the 'edit' button</span>
-<span id="L144" class="LineNr">144 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L173'>find-sandbox</a> env, click-row
-<span id="L145" class="LineNr">145 </span>  <span class="muControl">return-unless</span> sandbox, <span class="Constant">0/false</span>
-<span id="L146" class="LineNr">146 </span>  clicked-on-edit-button? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-<span id="L147" class="LineNr">147 </span>  <span class="Comment"># 'edit' button = 'copy' button + 'delete' button</span>
-<span id="L148" class="LineNr">148 </span>  text:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
-<span id="L149" class="LineNr">149 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L150" class="LineNr">150 </span>  current-sandbox <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L71'>insert-text</a> current-sandbox, text
-<span id="L151" class="LineNr">151 </span>  env <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L107'>delete-sandbox</a> env, sandbox
-<span id="L152" class="LineNr">152 </span>  <span class="Comment"># reset scroll</span>
-<span id="L153" class="LineNr">153 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>,<span class="Constant"> -1</span>
-<span id="L154" class="LineNr">154 </span>  <span class="Comment"># position cursor in sandbox editor</span>
-<span id="L155" class="LineNr">155 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, <span class="Constant">1/true</span>
-<span id="L156" class="LineNr">156 </span>]
-<span id="L157" class="LineNr">157 </span>
-<span id="L158" class="LineNr">158 </span><span class="muScenario">scenario</span> sandbox-with-print-can-be-edited [
-<span id="L159" class="LineNr">159 </span>  <span class="Constant">local-scope</span>
-<span id="L160" class="LineNr">160 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L161" class="LineNr">161 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
-<span id="L162" class="LineNr">162 </span>  <span class="Comment"># left editor is empty</span>
-<span id="L163" class="LineNr">163 </span>  assume-resources [
-<span id="L164" class="LineNr">164 </span>  ]
-<span id="L165" class="LineNr">165 </span>  <span class="Comment"># right editor contains a print instruction</span>
-<span id="L166" class="LineNr">166 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[print <a href='../081print.mu.html#L4'>screen</a>, 4]</span>
-<span id="L167" class="LineNr">167 </span>  <span class="Comment"># run the sandbox</span>
-<span id="L168" class="LineNr">168 </span>  assume-console [
-<span id="L169" class="LineNr">169 </span>  <span class="Conceal">¦</span> press F4
-<span id="L170" class="LineNr">170 </span>  ]
-<span id="L171" class="LineNr">171 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L172" class="LineNr">172 </span>  screen-should-contain [
-<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L175" class="LineNr">175 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎print <a href='../081print.mu.html#L4'>screen</a>, 4                                  .</span>
-<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎screen:                                          .</span>
-<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .4                             .               .</span>
-<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
-<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
+<span id="L114" class="LineNr">114 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L115" class="LineNr">115 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L116" class="LineNr">116 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L117" class="LineNr">117 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L118" class="LineNr">118 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L119" class="LineNr">119 </span>  <span class="Delimiter">}</span>
+<span id="L120" class="LineNr">120 </span>]
+<span id="L121" class="LineNr">121 </span>
+<span id="L122" class="LineNr">122 </span><span class="Comment"># some preconditions for attempting to edit a sandbox</span>
+<span id="L123" class="LineNr">123 </span><span class="muRecipe">def</span> <a href='008-sandbox-edit.mu.html#L123'>should-attempt-edit?</a> click-row:num, click-column:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>result:bool [
+<span id="L124" class="LineNr">124 </span>  <span class="Constant">local-scope</span>
+<span id="L125" class="LineNr">125 </span>  <span class="Constant">load-ingredients</span>
+<span id="L126" class="LineNr">126 </span>  <span class="Comment"># are we below the sandbox editor?</span>
+<span id="L127" class="LineNr">127 </span>  click-sandbox-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L190'>click-on-sandbox-area?</a> click-row, click-column, env
+<span id="L128" class="LineNr">128 </span>  <span class="muControl">return-unless</span> click-sandbox-area?, <span class="Constant">0/false</span>
+<span id="L129" class="LineNr">129 </span>  <span class="Comment"># narrower, is the click in the columns spanning the 'edit' button?</span>
+<span id="L130" class="LineNr">130 </span>  first-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L131" class="LineNr">131 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
+<span id="L132" class="LineNr">132 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
+<span id="L133" class="LineNr">133 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
+<span id="L134" class="LineNr">134 </span>  edit-button-left:num, edit-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L344'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
+<span id="L135" class="LineNr">135 </span>  edit-button-vertical-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L211'>within-range?</a> click-column, edit-button-left, edit-button-right
+<span id="L136" class="LineNr">136 </span>  <span class="muControl">return-unless</span> edit-button-vertical-area?, <span class="Constant">0/false</span>
+<span id="L137" class="LineNr">137 </span>  <span class="Comment"># finally, is sandbox editor empty?</span>
+<span id="L138" class="LineNr">138 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L139" class="LineNr">139 </span>  result <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L203'>empty-editor?</a> current-sandbox
+<span id="L140" class="LineNr">140 </span>]
+<span id="L141" class="LineNr">141 </span>
+<span id="L142" class="LineNr">142 </span><span class="muRecipe">def</span> <a href='008-sandbox-edit.mu.html#L142'>try-edit-sandbox</a> click-row:num, env:&amp;:environment<span class="muRecipe"> -&gt; </span>clicked-on-edit-button?:bool, env:&amp;:environment [
+<span id="L143" class="LineNr">143 </span>  <span class="Constant">local-scope</span>
+<span id="L144" class="LineNr">144 </span>  <span class="Constant">load-ingredients</span>
+<span id="L145" class="LineNr">145 </span>  <span class="Comment"># identify the sandbox to edit, if the click was actually on the 'edit' button</span>
+<span id="L146" class="LineNr">146 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L175'>find-sandbox</a> env, click-row
+<span id="L147" class="LineNr">147 </span>  <span class="muControl">return-unless</span> sandbox, <span class="Constant">0/false</span>
+<span id="L148" class="LineNr">148 </span>  clicked-on-edit-button? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
+<span id="L149" class="LineNr">149 </span>  <span class="Comment"># 'edit' button = 'copy' button + 'delete' button</span>
+<span id="L150" class="LineNr">150 </span>  text:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
+<span id="L151" class="LineNr">151 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L152" class="LineNr">152 </span>  current-sandbox <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L73'>insert-text</a> current-sandbox, text
+<span id="L153" class="LineNr">153 </span>  env <span class="Special">&lt;-</span> <a href='007-sandbox-delete.mu.html#L109'>delete-sandbox</a> env, sandbox
+<span id="L154" class="LineNr">154 </span>  <span class="Comment"># reset scroll</span>
+<span id="L155" class="LineNr">155 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>,<span class="Constant"> -1</span>
+<span id="L156" class="LineNr">156 </span>  <span class="Comment"># position cursor in sandbox editor</span>
+<span id="L157" class="LineNr">157 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox-in-focus?:offset</span>, <span class="Constant">1/true</span>
+<span id="L158" class="LineNr">158 </span>]
+<span id="L159" class="LineNr">159 </span>
+<span id="L160" class="LineNr">160 </span><span class="muScenario">scenario</span> sandbox-with-print-can-be-edited [
+<span id="L161" class="LineNr">161 </span>  <span class="Constant">local-scope</span>
+<span id="L162" class="LineNr">162 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L163" class="LineNr">163 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
+<span id="L164" class="LineNr">164 </span>  <span class="Comment"># left editor is empty</span>
+<span id="L165" class="LineNr">165 </span>  assume-resources [
+<span id="L166" class="LineNr">166 </span>  ]
+<span id="L167" class="LineNr">167 </span>  <span class="Comment"># right editor contains a print instruction</span>
+<span id="L168" class="LineNr">168 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[print <a href='../081print.mu.html#L4'>screen</a>, 4]</span>
+<span id="L169" class="LineNr">169 </span>  <span class="Comment"># run the sandbox</span>
+<span id="L170" class="LineNr">170 </span>  assume-console [
+<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span> press F4
+<span id="L172" class="LineNr">172 </span>  ]
+<span id="L173" class="LineNr">173 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L174" class="LineNr">174 </span>  screen-should-contain [
+<span id="L175" class="LineNr">175 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L177" class="LineNr">177 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎print <a href='../081print.mu.html#L4'>screen</a>, 4                                  .</span>
+<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎screen:                                          .</span>
+<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .4                             .               .</span>
 <span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
 <span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
-<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L186" class="LineNr">186 </span>  ]
-<span id="L187" class="LineNr">187 </span>  <span class="Comment"># edit the sandbox</span>
-<span id="L188" class="LineNr">188 </span>  assume-console [
-<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 65</span>
-<span id="L190" class="LineNr">190 </span>  ]
-<span id="L191" class="LineNr">191 </span>  run [
-<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L193" class="LineNr">193 </span>  ]
-<span id="L194" class="LineNr">194 </span>  screen-should-contain [
-<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎print <a href='../081print.mu.html#L4'>screen</a>, 4                                  .</span>
-<span id="L197" class="LineNr">197 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L200" class="LineNr">200 </span>  ]
-<span id="L201" class="LineNr">201 </span>]
-<span id="L202" class="LineNr">202 </span>
-<span id="L203" class="LineNr">203 </span><span class="muScenario">scenario</span> editing-sandbox-after-scrolling-resets-scroll [
-<span id="L204" class="LineNr">204 </span>  <span class="Constant">local-scope</span>
-<span id="L205" class="LineNr">205 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L206" class="LineNr">206 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L207" class="LineNr">207 </span>  <span class="Comment"># initialize environment</span>
-<span id="L208" class="LineNr">208 </span>  assume-resources [
-<span id="L209" class="LineNr">209 </span>  ]
-<span id="L210" class="LineNr">210 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L211" class="LineNr">211 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L212" class="LineNr">212 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
-<span id="L213" class="LineNr">213 </span>  assume-console [
-<span id="L214" class="LineNr">214 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L215" class="LineNr">215 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L216" class="LineNr">216 </span>  <span class="Conceal">¦</span> press F4
-<span id="L217" class="LineNr">217 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
+<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
+<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L188" class="LineNr">188 </span>  ]
+<span id="L189" class="LineNr">189 </span>  <span class="Comment"># edit the sandbox</span>
+<span id="L190" class="LineNr">190 </span>  assume-console [
+<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 65</span>
+<span id="L192" class="LineNr">192 </span>  ]
+<span id="L193" class="LineNr">193 </span>  run [
+<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L195" class="LineNr">195 </span>  ]
+<span id="L196" class="LineNr">196 </span>  screen-should-contain [
+<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎print <a href='../081print.mu.html#L4'>screen</a>, 4                                  .</span>
+<span id="L199" class="LineNr">199 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L201" class="LineNr">201 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L202" class="LineNr">202 </span>  ]
+<span id="L203" class="LineNr">203 </span>]
+<span id="L204" class="LineNr">204 </span>
+<span id="L205" class="LineNr">205 </span><span class="muScenario">scenario</span> editing-sandbox-after-scrolling-resets-scroll [
+<span id="L206" class="LineNr">206 </span>  <span class="Constant">local-scope</span>
+<span id="L207" class="LineNr">207 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L208" class="LineNr">208 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L209" class="LineNr">209 </span>  <span class="Comment"># initialize environment</span>
+<span id="L210" class="LineNr">210 </span>  assume-resources [
+<span id="L211" class="LineNr">211 </span>  ]
+<span id="L212" class="LineNr">212 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L213" class="LineNr">213 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L214" class="LineNr">214 </span>  <span class="Comment"># create 2 sandboxes and scroll to second</span>
+<span id="L215" class="LineNr">215 </span>  assume-console [
+<span id="L216" class="LineNr">216 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L217" class="LineNr">217 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
 <span id="L218" class="LineNr">218 </span>  <span class="Conceal">¦</span> press F4
-<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L220" class="LineNr">220 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L221" class="LineNr">221 </span>  ]
-<span id="L222" class="LineNr">222 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L223" class="LineNr">223 </span>  screen-should-contain [
-<span id="L224" class="LineNr">224 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L225" class="LineNr">225 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L226" class="LineNr">226 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
-<span id="L227" class="LineNr">227 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L228" class="LineNr">228 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L229" class="LineNr">229 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L230" class="LineNr">230 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L231" class="LineNr">231 </span>  ]
-<span id="L232" class="LineNr">232 </span>  <span class="Comment"># edit the second sandbox</span>
-<span id="L233" class="LineNr">233 </span>  assume-console [
-<span id="L234" class="LineNr">234 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 55</span>
-<span id="L235" class="LineNr">235 </span>  ]
-<span id="L236" class="LineNr">236 </span>  run [
-<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L238" class="LineNr">238 </span>  ]
-<span id="L239" class="LineNr">239 </span>  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
-<span id="L240" class="LineNr">240 </span>  screen-should-contain [
-<span id="L241" class="LineNr">241 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L242" class="LineNr">242 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L243" class="LineNr">243 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L247" class="LineNr">247 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L248" class="LineNr">248 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L249" class="LineNr">249 </span>  ]
-<span id="L250" class="LineNr">250 </span>]
-<span id="L251" class="LineNr">251 </span>
-<span id="L252" class="LineNr">252 </span><span class="muScenario">scenario</span> editing-sandbox-updates-sandbox-count [
-<span id="L253" class="LineNr">253 </span>  <span class="Constant">local-scope</span>
-<span id="L254" class="LineNr">254 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L255" class="LineNr">255 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L256" class="LineNr">256 </span>  <span class="Comment"># initialize environment</span>
-<span id="L257" class="LineNr">257 </span>  assume-resources [
-<span id="L258" class="LineNr">258 </span>  ]
-<span id="L259" class="LineNr">259 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L260" class="LineNr">260 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L261" class="LineNr">261 </span>  <span class="Comment"># create 2 sandboxes</span>
-<span id="L262" class="LineNr">262 </span>  assume-console [
-<span id="L263" class="LineNr">263 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L264" class="LineNr">264 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span> press F4
-<span id="L266" class="LineNr">266 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L220" class="LineNr">220 </span>  <span class="Conceal">¦</span> press F4
+<span id="L221" class="LineNr">221 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L222" class="LineNr">222 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L223" class="LineNr">223 </span>  ]
+<span id="L224" class="LineNr">224 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L225" class="LineNr">225 </span>  screen-should-contain [
+<span id="L226" class="LineNr">226 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L227" class="LineNr">227 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L228" class="LineNr">228 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
+<span id="L229" class="LineNr">229 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L230" class="LineNr">230 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L231" class="LineNr">231 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L232" class="LineNr">232 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L233" class="LineNr">233 </span>  ]
+<span id="L234" class="LineNr">234 </span>  <span class="Comment"># edit the second sandbox</span>
+<span id="L235" class="LineNr">235 </span>  assume-console [
+<span id="L236" class="LineNr">236 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 2</span>,<span class="Constant"> 55</span>
+<span id="L237" class="LineNr">237 </span>  ]
+<span id="L238" class="LineNr">238 </span>  run [
+<span id="L239" class="LineNr">239 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L240" class="LineNr">240 </span>  ]
+<span id="L241" class="LineNr">241 </span>  <span class="Comment"># second sandbox shows in editor; scroll resets to display first sandbox</span>
+<span id="L242" class="LineNr">242 </span>  screen-should-contain [
+<span id="L243" class="LineNr">243 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L245" class="LineNr">245 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L247" class="LineNr">247 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L248" class="LineNr">248 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L250" class="LineNr">250 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L251" class="LineNr">251 </span>  ]
+<span id="L252" class="LineNr">252 </span>]
+<span id="L253" class="LineNr">253 </span>
+<span id="L254" class="LineNr">254 </span><span class="muScenario">scenario</span> editing-sandbox-updates-sandbox-count [
+<span id="L255" class="LineNr">255 </span>  <span class="Constant">local-scope</span>
+<span id="L256" class="LineNr">256 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L257" class="LineNr">257 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L258" class="LineNr">258 </span>  <span class="Comment"># initialize environment</span>
+<span id="L259" class="LineNr">259 </span>  assume-resources [
+<span id="L260" class="LineNr">260 </span>  ]
+<span id="L261" class="LineNr">261 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L262" class="LineNr">262 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L263" class="LineNr">263 </span>  <span class="Comment"># create 2 sandboxes</span>
+<span id="L264" class="LineNr">264 </span>  assume-console [
+<span id="L265" class="LineNr">265 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L266" class="LineNr">266 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
 <span id="L267" class="LineNr">267 </span>  <span class="Conceal">¦</span> press F4
-<span id="L268" class="LineNr">268 </span>  ]
-<span id="L269" class="LineNr">269 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L270" class="LineNr">270 </span>  screen-should-contain [
-<span id="L271" class="LineNr">271 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L272" class="LineNr">272 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L273" class="LineNr">273 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L274" class="LineNr">274 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L275" class="LineNr">275 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L276" class="LineNr">276 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L278" class="LineNr">278 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L279" class="LineNr">279 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L280" class="LineNr">280 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L281" class="LineNr">281 </span>  ]
-<span id="L282" class="LineNr">282 </span>  <span class="Comment"># edit the second sandbox, then resave</span>
-<span id="L283" class="LineNr">283 </span>  assume-console [
-<span id="L284" class="LineNr">284 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 60</span>
-<span id="L285" class="LineNr">285 </span>  <span class="Conceal">¦</span> press F4
-<span id="L286" class="LineNr">286 </span>  ]
-<span id="L287" class="LineNr">287 </span>  run [
-<span id="L288" class="LineNr">288 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L289" class="LineNr">289 </span>  ]
-<span id="L290" class="LineNr">290 </span>  <span class="Comment"># no change in contents</span>
-<span id="L291" class="LineNr">291 </span>  screen-should-contain [
-<span id="L292" class="LineNr">292 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L293" class="LineNr">293 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L294" class="LineNr">294 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L295" class="LineNr">295 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L296" class="LineNr">296 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L297" class="LineNr">297 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L298" class="LineNr">298 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L299" class="LineNr">299 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L300" class="LineNr">300 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L301" class="LineNr">301 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L302" class="LineNr">302 </span>  ]
-<span id="L303" class="LineNr">303 </span>  <span class="Comment"># now try to scroll past end</span>
-<span id="L304" class="LineNr">304 </span>  assume-console [
-<span id="L305" class="LineNr">305 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L306" class="LineNr">306 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L268" class="LineNr">268 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L269" class="LineNr">269 </span>  <span class="Conceal">¦</span> press F4
+<span id="L270" class="LineNr">270 </span>  ]
+<span id="L271" class="LineNr">271 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L272" class="LineNr">272 </span>  screen-should-contain [
+<span id="L273" class="LineNr">273 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L274" class="LineNr">274 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L275" class="LineNr">275 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L276" class="LineNr">276 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L278" class="LineNr">278 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L279" class="LineNr">279 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L280" class="LineNr">280 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L281" class="LineNr">281 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L282" class="LineNr">282 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L283" class="LineNr">283 </span>  ]
+<span id="L284" class="LineNr">284 </span>  <span class="Comment"># edit the second sandbox, then resave</span>
+<span id="L285" class="LineNr">285 </span>  assume-console [
+<span id="L286" class="LineNr">286 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 60</span>
+<span id="L287" class="LineNr">287 </span>  <span class="Conceal">¦</span> press F4
+<span id="L288" class="LineNr">288 </span>  ]
+<span id="L289" class="LineNr">289 </span>  run [
+<span id="L290" class="LineNr">290 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L291" class="LineNr">291 </span>  ]
+<span id="L292" class="LineNr">292 </span>  <span class="Comment"># no change in contents</span>
+<span id="L293" class="LineNr">293 </span>  screen-should-contain [
+<span id="L294" class="LineNr">294 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L295" class="LineNr">295 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L296" class="LineNr">296 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L297" class="LineNr">297 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L298" class="LineNr">298 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L299" class="LineNr">299 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L300" class="LineNr">300 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L301" class="LineNr">301 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L302" class="LineNr">302 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L303" class="LineNr">303 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L304" class="LineNr">304 </span>  ]
+<span id="L305" class="LineNr">305 </span>  <span class="Comment"># now try to scroll past end</span>
+<span id="L306" class="LineNr">306 </span>  assume-console [
 <span id="L307" class="LineNr">307 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L308" class="LineNr">308 </span>  ]
-<span id="L309" class="LineNr">309 </span>  run [
-<span id="L310" class="LineNr">310 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L311" class="LineNr">311 </span>  ]
-<span id="L312" class="LineNr">312 </span>  <span class="Comment"># screen should show just final sandbox with the right index (1)</span>
-<span id="L313" class="LineNr">313 </span>  screen-should-contain [
-<span id="L314" class="LineNr">314 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L315" class="LineNr">315 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
-<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L318" class="LineNr">318 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L320" class="LineNr">320 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L321" class="LineNr">321 </span>  ]
-<span id="L322" class="LineNr">322 </span>]
+<span id="L308" class="LineNr">308 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L309" class="LineNr">309 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L310" class="LineNr">310 </span>  ]
+<span id="L311" class="LineNr">311 </span>  run [
+<span id="L312" class="LineNr">312 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L313" class="LineNr">313 </span>  ]
+<span id="L314" class="LineNr">314 </span>  <span class="Comment"># screen should show just final sandbox with the right index (1)</span>
+<span id="L315" class="LineNr">315 </span>  screen-should-contain [
+<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L318" class="LineNr">318 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
+<span id="L319" class="LineNr">319 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L320" class="LineNr">320 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L321" class="LineNr">321 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L322" class="LineNr">322 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L323" class="LineNr">323 </span>  ]
+<span id="L324" class="LineNr">324 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/009-sandbox-test.mu.html b/html/edit/009-sandbox-test.mu.html
index baa7c1ba..80242905 100644
--- a/html/edit/009-sandbox-test.mu.html
+++ b/html/edit/009-sandbox-test.mu.html
@@ -174,7 +174,7 @@ if ('onhashchange' in window) {
 <span id="L111" class="LineNr">111 </span>]
 <span id="L112" class="LineNr">112 </span>
 <span id="L113" class="LineNr">113 </span><span class="Comment"># clicks on sandbox responses save it as 'expected'</span>
-<span id="L114" class="LineNr">114 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L76'>&lt;global-touch&gt;</a></span> [
+<span id="L114" class="LineNr">114 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L80'>&lt;global-touch&gt;</a></span> [
 <span id="L115" class="LineNr">115 </span>  <span class="Comment"># check if it's inside the output of any sandbox</span>
 <span id="L116" class="LineNr">116 </span>  <span class="Delimiter">{</span>
 <span id="L117" class="LineNr">117 </span>  <span class="Conceal">¦</span> sandbox-left-margin:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
@@ -188,83 +188,85 @@ if ('onhashchange' in window) {
 <span id="L125" class="LineNr">125 </span>  <span class="Conceal">¦</span> below-sandbox-editor?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, first-sandbox-begins
 <span id="L126" class="LineNr">126 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> below-sandbox-editor?
 <span id="L127" class="LineNr">127 </span>  <span class="Conceal">¦</span> <span class="Comment"># identify the sandbox whose output is being clicked on</span>
-<span id="L128" class="LineNr">128 </span>  <span class="Conceal">¦</span> sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='009-sandbox-test.mu.html#L139'>find-click-in-sandbox-output</a> env, click-row
+<span id="L128" class="LineNr">128 </span>  <span class="Conceal">¦</span> sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='009-sandbox-test.mu.html#L141'>find-click-in-sandbox-output</a> env, click-row
 <span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox
 <span id="L130" class="LineNr">130 </span>  <span class="Conceal">¦</span> <span class="Comment"># toggle its expected-response, and save session</span>
-<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> sandbox <span class="Special">&lt;-</span> <a href='009-sandbox-test.mu.html#L165'>toggle-expected-response</a> sandbox
+<span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> sandbox <span class="Special">&lt;-</span> <a href='009-sandbox-test.mu.html#L167'>toggle-expected-response</a> sandbox
 <span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L220'>save-sandboxes</a> env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L135" class="LineNr">135 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L136" class="LineNr">136 </span>  <span class="Delimiter">}</span>
-<span id="L137" class="LineNr">137 </span>]
-<span id="L138" class="LineNr">138 </span>
-<span id="L139" class="LineNr">139 </span><span class="muRecipe">def</span> <a href='009-sandbox-test.mu.html#L139'>find-click-in-sandbox-output</a> env:&amp;:environment, click-row:num<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox [
-<span id="L140" class="LineNr">140 </span>  <span class="Constant">local-scope</span>
-<span id="L141" class="LineNr">141 </span>  <span class="Constant">load-ingredients</span>
-<span id="L142" class="LineNr">142 </span>  <span class="Comment"># assert click-row &gt;= sandbox.starting-row-on-screen</span>
-<span id="L143" class="LineNr">143 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L144" class="LineNr">144 </span>  start:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-<span id="L145" class="LineNr">145 </span>  clicked-on-sandboxes?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, start
-<span id="L146" class="LineNr">146 </span>  assert clicked-on-sandboxes?, <span class="Constant">[extract-sandbox called on click to sandbox editor]</span>
-<span id="L147" class="LineNr">147 </span>  <span class="Comment"># while click-row &lt; sandbox.next-sandbox.starting-row-on-screen</span>
-<span id="L148" class="LineNr">148 </span>  <span class="Delimiter">{</span>
-<span id="L149" class="LineNr">149 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L150" class="LineNr">150 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> next-sandbox
-<span id="L151" class="LineNr">151 </span>  <span class="Conceal">¦</span> next-start:num <span class="Special">&lt;-</span> get *next-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-<span id="L152" class="LineNr">152 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> lesser-than click-row, next-start
-<span id="L153" class="LineNr">153 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
-<span id="L154" class="LineNr">154 </span>  <span class="Conceal">¦</span> sandbox <span class="Special">&lt;-</span> copy next-sandbox
-<span id="L155" class="LineNr">155 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L156" class="LineNr">156 </span>  <span class="Delimiter">}</span>
-<span id="L157" class="LineNr">157 </span>  <span class="Comment"># return sandbox if click is in its output region</span>
-<span id="L158" class="LineNr">158 </span>  response-starting-row:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>
-<span id="L159" class="LineNr">159 </span>  <span class="muControl">return-unless</span> response-starting-row, <span class="Constant">0/no-click-in-sandbox-output</span>
-<span id="L160" class="LineNr">160 </span>  click-in-response?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, response-starting-row
-<span id="L161" class="LineNr">161 </span>  <span class="muControl">return-unless</span> click-in-response?, <span class="Constant">0/no-click-in-sandbox-output</span>
-<span id="L162" class="LineNr">162 </span>  <span class="muControl">return</span> sandbox
-<span id="L163" class="LineNr">163 </span>]
-<span id="L164" class="LineNr">164 </span>
-<span id="L165" class="LineNr">165 </span><span class="muRecipe">def</span> <a href='009-sandbox-test.mu.html#L165'>toggle-expected-response</a> sandbox:&amp;:sandbox<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox [
-<span id="L166" class="LineNr">166 </span>  <span class="Constant">local-scope</span>
-<span id="L167" class="LineNr">167 </span>  <span class="Constant">load-ingredients</span>
-<span id="L168" class="LineNr">168 </span>  expected-response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">expected-response:offset</span>
-<span id="L169" class="LineNr">169 </span>  <span class="Delimiter">{</span>
-<span id="L170" class="LineNr">170 </span>  <span class="Conceal">¦</span> <span class="Comment"># if expected-response is set, reset</span>
-<span id="L171" class="LineNr">171 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> expected-response
-<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">expected-response:offset</span>,<span class="Constant"> 0</span>
-<span id="L173" class="LineNr">173 </span>  <span class="Delimiter">}</span>
-<span id="L174" class="LineNr">174 </span>  <span class="Delimiter">{</span>
-<span id="L175" class="LineNr">175 </span>  <span class="Conceal">¦</span> <span class="Comment"># if not, set expected response to the current response</span>
-<span id="L176" class="LineNr">176 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> expected-response
-<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span> response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">response:offset</span>
-<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">expected-response:offset</span>, response
-<span id="L179" class="LineNr">179 </span>  <span class="Delimiter">}</span>
-<span id="L180" class="LineNr">180 </span>]
-<span id="L181" class="LineNr">181 </span>
-<span id="L182" class="LineNr">182 </span><span class="Comment"># when rendering a sandbox, color it in red/green if expected response exists</span>
-<span id="L183" class="LineNr">183 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L297'>&lt;render-sandbox-response&gt;</a></span> [
-<span id="L184" class="LineNr">184 </span>  <span class="Delimiter">{</span>
-<span id="L185" class="LineNr">185 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-response
-<span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>, row
-<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span> expected-response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">expected-response:offset</span>
-<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> expected-response  <span class="Comment"># fall-through to print in grey</span>
-<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> response-is-expected?:bool <span class="Special">&lt;-</span> equal expected-response, sandbox-response
-<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> response-is-expected?:bool
-<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">1/red</span>, row
-<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> response-is-expected?:bool
-<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">2/green</span>, row
-<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+render-sandbox-end</span>
-<span id="L199" class="LineNr">199 </span>  <span class="Delimiter">}</span>
-<span id="L200" class="LineNr">200 </span>]
-<span id="L201" class="LineNr">201 </span>
-<span id="L202" class="LineNr">202 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L311'>&lt;end-render-sandbox-reset-hidden&gt;</a></span> [
-<span id="L203" class="LineNr">203 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>,<span class="Constant"> 0</span>
-<span id="L204" class="LineNr">204 </span>]
+<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L135" class="LineNr">135 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L136" class="LineNr">136 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L137" class="LineNr">137 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L138" class="LineNr">138 </span>  <span class="Delimiter">}</span>
+<span id="L139" class="LineNr">139 </span>]
+<span id="L140" class="LineNr">140 </span>
+<span id="L141" class="LineNr">141 </span><span class="muRecipe">def</span> <a href='009-sandbox-test.mu.html#L141'>find-click-in-sandbox-output</a> env:&amp;:environment, click-row:num<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox [
+<span id="L142" class="LineNr">142 </span>  <span class="Constant">local-scope</span>
+<span id="L143" class="LineNr">143 </span>  <span class="Constant">load-ingredients</span>
+<span id="L144" class="LineNr">144 </span>  <span class="Comment"># assert click-row &gt;= sandbox.starting-row-on-screen</span>
+<span id="L145" class="LineNr">145 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L146" class="LineNr">146 </span>  start:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+<span id="L147" class="LineNr">147 </span>  clicked-on-sandboxes?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, start
+<span id="L148" class="LineNr">148 </span>  assert clicked-on-sandboxes?, <span class="Constant">[extract-sandbox called on click to sandbox editor]</span>
+<span id="L149" class="LineNr">149 </span>  <span class="Comment"># while click-row &lt; sandbox.next-sandbox.starting-row-on-screen</span>
+<span id="L150" class="LineNr">150 </span>  <span class="Delimiter">{</span>
+<span id="L151" class="LineNr">151 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L152" class="LineNr">152 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> next-sandbox
+<span id="L153" class="LineNr">153 </span>  <span class="Conceal">¦</span> next-start:num <span class="Special">&lt;-</span> get *next-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+<span id="L154" class="LineNr">154 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> lesser-than click-row, next-start
+<span id="L155" class="LineNr">155 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
+<span id="L156" class="LineNr">156 </span>  <span class="Conceal">¦</span> sandbox <span class="Special">&lt;-</span> copy next-sandbox
+<span id="L157" class="LineNr">157 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L158" class="LineNr">158 </span>  <span class="Delimiter">}</span>
+<span id="L159" class="LineNr">159 </span>  <span class="Comment"># return sandbox if click is in its output region</span>
+<span id="L160" class="LineNr">160 </span>  response-starting-row:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>
+<span id="L161" class="LineNr">161 </span>  <span class="muControl">return-unless</span> response-starting-row, <span class="Constant">0/no-click-in-sandbox-output</span>
+<span id="L162" class="LineNr">162 </span>  click-in-response?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, response-starting-row
+<span id="L163" class="LineNr">163 </span>  <span class="muControl">return-unless</span> click-in-response?, <span class="Constant">0/no-click-in-sandbox-output</span>
+<span id="L164" class="LineNr">164 </span>  <span class="muControl">return</span> sandbox
+<span id="L165" class="LineNr">165 </span>]
+<span id="L166" class="LineNr">166 </span>
+<span id="L167" class="LineNr">167 </span><span class="muRecipe">def</span> <a href='009-sandbox-test.mu.html#L167'>toggle-expected-response</a> sandbox:&amp;:sandbox<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox [
+<span id="L168" class="LineNr">168 </span>  <span class="Constant">local-scope</span>
+<span id="L169" class="LineNr">169 </span>  <span class="Constant">load-ingredients</span>
+<span id="L170" class="LineNr">170 </span>  expected-response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">expected-response:offset</span>
+<span id="L171" class="LineNr">171 </span>  <span class="Delimiter">{</span>
+<span id="L172" class="LineNr">172 </span>  <span class="Conceal">¦</span> <span class="Comment"># if expected-response is set, reset</span>
+<span id="L173" class="LineNr">173 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> expected-response
+<span id="L174" class="LineNr">174 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">expected-response:offset</span>,<span class="Constant"> 0</span>
+<span id="L175" class="LineNr">175 </span>  <span class="Delimiter">}</span>
+<span id="L176" class="LineNr">176 </span>  <span class="Delimiter">{</span>
+<span id="L177" class="LineNr">177 </span>  <span class="Conceal">¦</span> <span class="Comment"># if not, set expected response to the current response</span>
+<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> expected-response
+<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span> response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">response:offset</span>
+<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">expected-response:offset</span>, response
+<span id="L181" class="LineNr">181 </span>  <span class="Delimiter">}</span>
+<span id="L182" class="LineNr">182 </span>]
+<span id="L183" class="LineNr">183 </span>
+<span id="L184" class="LineNr">184 </span><span class="Comment"># when rendering a sandbox, color it in red/green if expected response exists</span>
+<span id="L185" class="LineNr">185 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L297'>&lt;render-sandbox-response&gt;</a></span> [
+<span id="L186" class="LineNr">186 </span>  <span class="Delimiter">{</span>
+<span id="L187" class="LineNr">187 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-response
+<span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>, row
+<span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> expected-response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">expected-response:offset</span>
+<span id="L190" class="LineNr">190 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> expected-response  <span class="Comment"># fall-through to print in grey</span>
+<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span> response-is-expected?:bool <span class="Special">&lt;-</span> equal expected-response, sandbox-response
+<span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> response-is-expected?:bool
+<span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">1/red</span>, row
+<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> response-is-expected?:bool
+<span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">2/green</span>, row
+<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+render-sandbox-end</span>
+<span id="L201" class="LineNr">201 </span>  <span class="Delimiter">}</span>
+<span id="L202" class="LineNr">202 </span>]
+<span id="L203" class="LineNr">203 </span>
+<span id="L204" class="LineNr">204 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L311'>&lt;end-render-sandbox-reset-hidden&gt;</a></span> [
+<span id="L205" class="LineNr">205 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>,<span class="Constant"> 0</span>
+<span id="L206" class="LineNr">206 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/010-sandbox-trace.mu.html b/html/edit/010-sandbox-trace.mu.html
index e1a98ad8..c1950605 100644
--- a/html/edit/010-sandbox-trace.mu.html
+++ b/html/edit/010-sandbox-trace.mu.html
@@ -243,7 +243,7 @@ if ('onhashchange' in window) {
 <span id="L180" class="LineNr">180 </span>]
 <span id="L181" class="LineNr">181 </span>
 <span id="L182" class="LineNr">182 </span><span class="Comment"># clicks on sandbox code toggle its display-trace? flag</span>
-<span id="L183" class="LineNr">183 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L76'>&lt;global-touch&gt;</a></span> [
+<span id="L183" class="LineNr">183 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L80'>&lt;global-touch&gt;</a></span> [
 <span id="L184" class="LineNr">184 </span>  <span class="Comment"># check if it's inside the code of any sandbox</span>
 <span id="L185" class="LineNr">185 </span>  <span class="Delimiter">{</span>
 <span id="L186" class="LineNr">186 </span>  <span class="Conceal">¦</span> sandbox-left-margin:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
@@ -257,60 +257,62 @@ if ('onhashchange' in window) {
 <span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> below-sandbox-editor?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, first-sandbox-begins
 <span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> below-sandbox-editor?
 <span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> <span class="Comment"># identify the sandbox whose code is being clicked on</span>
-<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='010-sandbox-trace.mu.html#L209'>find-click-in-sandbox-code</a> env, click-row
+<span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> sandbox:&amp;:sandbox <span class="Special">&lt;-</span> <a href='010-sandbox-trace.mu.html#L211'>find-click-in-sandbox-code</a> env, click-row
 <span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox
 <span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> <span class="Comment"># toggle its display-trace? property</span>
 <span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span> x:bool <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">display-trace?:offset</span>
 <span id="L201" class="LineNr">201 </span>  <span class="Conceal">¦</span> x <span class="Special">&lt;-</span> not x
 <span id="L202" class="LineNr">202 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">display-trace?:offset</span>, x
-<span id="L203" class="LineNr">203 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
-<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L446'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
-<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L206" class="LineNr">206 </span>  <span class="Delimiter">}</span>
-<span id="L207" class="LineNr">207 </span>]
-<span id="L208" class="LineNr">208 </span>
-<span id="L209" class="LineNr">209 </span><span class="muRecipe">def</span> <a href='010-sandbox-trace.mu.html#L209'>find-click-in-sandbox-code</a> env:&amp;:environment, click-row:num<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox [
-<span id="L210" class="LineNr">210 </span>  <span class="Constant">local-scope</span>
-<span id="L211" class="LineNr">211 </span>  <span class="Constant">load-ingredients</span>
-<span id="L212" class="LineNr">212 </span>  <span class="Comment"># assert click-row &gt;= sandbox.starting-row-on-screen</span>
-<span id="L213" class="LineNr">213 </span>  sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L214" class="LineNr">214 </span>  start:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-<span id="L215" class="LineNr">215 </span>  clicked-on-sandboxes?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, start
-<span id="L216" class="LineNr">216 </span>  assert clicked-on-sandboxes?, <span class="Constant">[extract-sandbox called on click to sandbox editor]</span>
-<span id="L217" class="LineNr">217 </span>  <span class="Comment"># while click-row &lt; sandbox.next-sandbox.starting-row-on-screen</span>
-<span id="L218" class="LineNr">218 </span>  <span class="Delimiter">{</span>
-<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L220" class="LineNr">220 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> next-sandbox
-<span id="L221" class="LineNr">221 </span>  <span class="Conceal">¦</span> next-start:num <span class="Special">&lt;-</span> get *next-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-<span id="L222" class="LineNr">222 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> lesser-than click-row, next-start
-<span id="L223" class="LineNr">223 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
-<span id="L224" class="LineNr">224 </span>  <span class="Conceal">¦</span> sandbox <span class="Special">&lt;-</span> copy next-sandbox
-<span id="L225" class="LineNr">225 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L226" class="LineNr">226 </span>  <span class="Delimiter">}</span>
-<span id="L227" class="LineNr">227 </span>  <span class="Comment"># return sandbox if click is in its code region</span>
-<span id="L228" class="LineNr">228 </span>  code-ending-row:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>
-<span id="L229" class="LineNr">229 </span>  click-above-response?:bool <span class="Special">&lt;-</span> lesser-than click-row, code-ending-row
-<span id="L230" class="LineNr">230 </span>  start:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
-<span id="L231" class="LineNr">231 </span>  click-below-menu?:bool <span class="Special">&lt;-</span> greater-than click-row, start
-<span id="L232" class="LineNr">232 </span>  click-on-sandbox-code?:bool <span class="Special">&lt;-</span> and click-above-response?, click-below-menu?
-<span id="L233" class="LineNr">233 </span>  <span class="Delimiter">{</span>
-<span id="L234" class="LineNr">234 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> click-on-sandbox-code?
-<span id="L235" class="LineNr">235 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">0/no-click-in-sandbox-output</span>
-<span id="L236" class="LineNr">236 </span>  <span class="Delimiter">}</span>
-<span id="L237" class="LineNr">237 </span>  <span class="muControl">return</span> sandbox
-<span id="L238" class="LineNr">238 </span>]
-<span id="L239" class="LineNr">239 </span>
-<span id="L240" class="LineNr">240 </span><span class="Comment"># when rendering a sandbox, dump its trace before response/warning if display-trace? property is set</span>
-<span id="L241" class="LineNr">241 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L288'>&lt;render-sandbox-results&gt;</a></span> [
-<span id="L242" class="LineNr">242 </span>  <span class="Delimiter">{</span>
-<span id="L243" class="LineNr">243 </span>  <span class="Conceal">¦</span> display-trace?:bool <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">display-trace?:offset</span>
-<span id="L244" class="LineNr">244 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> display-trace?
-<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span> sandbox-trace:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">trace:offset</span>
-<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-trace  <span class="Comment"># nothing to print; move on</span>
-<span id="L247" class="LineNr">247 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-trace, left, right, <span class="Constant">245/grey</span>, row
-<span id="L248" class="LineNr">248 </span>  <span class="Delimiter">}</span>
-<span id="L249" class="LineNr">249 </span><span class="Constant">  <a href='010-sandbox-trace.mu.html#L249'>&lt;render-sandbox-trace-done&gt;</a></span>
-<span id="L250" class="LineNr">250 </span>]
+<span id="L203" class="LineNr">203 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L460'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
+<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L208" class="LineNr">208 </span>  <span class="Delimiter">}</span>
+<span id="L209" class="LineNr">209 </span>]
+<span id="L210" class="LineNr">210 </span>
+<span id="L211" class="LineNr">211 </span><span class="muRecipe">def</span> <a href='010-sandbox-trace.mu.html#L211'>find-click-in-sandbox-code</a> env:&amp;:environment, click-row:num<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox [
+<span id="L212" class="LineNr">212 </span>  <span class="Constant">local-scope</span>
+<span id="L213" class="LineNr">213 </span>  <span class="Constant">load-ingredients</span>
+<span id="L214" class="LineNr">214 </span>  <span class="Comment"># assert click-row &gt;= sandbox.starting-row-on-screen</span>
+<span id="L215" class="LineNr">215 </span>  sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L216" class="LineNr">216 </span>  start:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+<span id="L217" class="LineNr">217 </span>  clicked-on-sandboxes?:bool <span class="Special">&lt;-</span> greater-or-equal click-row, start
+<span id="L218" class="LineNr">218 </span>  assert clicked-on-sandboxes?, <span class="Constant">[extract-sandbox called on click to sandbox editor]</span>
+<span id="L219" class="LineNr">219 </span>  <span class="Comment"># while click-row &lt; sandbox.next-sandbox.starting-row-on-screen</span>
+<span id="L220" class="LineNr">220 </span>  <span class="Delimiter">{</span>
+<span id="L221" class="LineNr">221 </span>  <span class="Conceal">¦</span> next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L222" class="LineNr">222 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> next-sandbox
+<span id="L223" class="LineNr">223 </span>  <span class="Conceal">¦</span> next-start:num <span class="Special">&lt;-</span> get *next-sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+<span id="L224" class="LineNr">224 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> lesser-than click-row, next-start
+<span id="L225" class="LineNr">225 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
+<span id="L226" class="LineNr">226 </span>  <span class="Conceal">¦</span> sandbox <span class="Special">&lt;-</span> copy next-sandbox
+<span id="L227" class="LineNr">227 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L228" class="LineNr">228 </span>  <span class="Delimiter">}</span>
+<span id="L229" class="LineNr">229 </span>  <span class="Comment"># return sandbox if click is in its code region</span>
+<span id="L230" class="LineNr">230 </span>  code-ending-row:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>
+<span id="L231" class="LineNr">231 </span>  click-above-response?:bool <span class="Special">&lt;-</span> lesser-than click-row, code-ending-row
+<span id="L232" class="LineNr">232 </span>  start:num <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">starting-row-on-screen:offset</span>
+<span id="L233" class="LineNr">233 </span>  click-below-menu?:bool <span class="Special">&lt;-</span> greater-than click-row, start
+<span id="L234" class="LineNr">234 </span>  click-on-sandbox-code?:bool <span class="Special">&lt;-</span> and click-above-response?, click-below-menu?
+<span id="L235" class="LineNr">235 </span>  <span class="Delimiter">{</span>
+<span id="L236" class="LineNr">236 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> click-on-sandbox-code?
+<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span> <span class="Constant">0/no-click-in-sandbox-output</span>
+<span id="L238" class="LineNr">238 </span>  <span class="Delimiter">}</span>
+<span id="L239" class="LineNr">239 </span>  <span class="muControl">return</span> sandbox
+<span id="L240" class="LineNr">240 </span>]
+<span id="L241" class="LineNr">241 </span>
+<span id="L242" class="LineNr">242 </span><span class="Comment"># when rendering a sandbox, dump its trace before response/warning if display-trace? property is set</span>
+<span id="L243" class="LineNr">243 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L288'>&lt;render-sandbox-results&gt;</a></span> [
+<span id="L244" class="LineNr">244 </span>  <span class="Delimiter">{</span>
+<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span> display-trace?:bool <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">display-trace?:offset</span>
+<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> display-trace?
+<span id="L247" class="LineNr">247 </span>  <span class="Conceal">¦</span> sandbox-trace:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">trace:offset</span>
+<span id="L248" class="LineNr">248 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-trace  <span class="Comment"># nothing to print; move on</span>
+<span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L361'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-trace, left, right, <span class="Constant">245/grey</span>, row
+<span id="L250" class="LineNr">250 </span>  <span class="Delimiter">}</span>
+<span id="L251" class="LineNr">251 </span><span class="Constant">  <a href='010-sandbox-trace.mu.html#L251'>&lt;render-sandbox-trace-done&gt;</a></span>
+<span id="L252" class="LineNr">252 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/011-errors.mu.html b/html/edit/011-errors.mu.html
index f40faa20..4d09cebb 100644
--- a/html/edit/011-errors.mu.html
+++ b/html/edit/011-errors.mu.html
@@ -86,7 +86,7 @@ if ('onhashchange' in window) {
 <span id="L23" class="LineNr"> 23 </span>  errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
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 <span id="L25" class="LineNr"> 25 </span>
-<span id="L26" class="LineNr"> 26 </span><span class="muRecipe">before</span> <span class="Constant"><a href='004-programming-environment.mu.html#L404'>&lt;render-components-end&gt;</a></span> [
+<span id="L26" class="LineNr"> 26 </span><span class="muRecipe">before</span> <span class="Constant"><a href='004-programming-environment.mu.html#L416'>&lt;render-components-end&gt;</a></span> [
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 <span id="L28" class="LineNr"> 28 </span>  recipe-errors:text <span class="Special">&lt;-</span> get *env, <span class="Constant">recipe-errors:offset</span>
 <span id="L29" class="LineNr"> 29 </span>  <span class="Delimiter">{</span>
@@ -95,7 +95,7 @@ if ('onhashchange' in window) {
 <span id="L32" class="LineNr"> 32 </span>  <span class="Delimiter">}</span>
 <span id="L33" class="LineNr"> 33 </span>]
 <span id="L34" class="LineNr"> 34 </span>
-<span id="L35" class="LineNr"> 35 </span><span class="muRecipe">before</span> <span class="Constant"><a href='004-programming-environment.mu.html#L423'>&lt;render-recipe-components-end&gt;</a></span> [
+<span id="L35" class="LineNr"> 35 </span><span class="muRecipe">before</span> <span class="Constant"><a href='004-programming-environment.mu.html#L437'>&lt;render-recipe-components-end&gt;</a></span> [
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 <span id="L37" class="LineNr"> 37 </span>  <span class="Conceal">¦</span> recipe-errors:text <span class="Special">&lt;-</span> get *env, <span class="Constant">recipe-errors:offset</span>
 <span id="L38" class="LineNr"> 38 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> recipe-errors
@@ -124,7 +124,7 @@ if ('onhashchange' in window) {
 <span id="L61" class="LineNr"> 61 </span>  <span class="Delimiter">}</span>
 <span id="L62" class="LineNr"> 62 </span>]
 <span id="L63" class="LineNr"> 63 </span>
-<span id="L64" class="LineNr"> 64 </span><span class="muRecipe">before</span> <span class="Constant"><a href='004-programming-environment.mu.html#L404'>&lt;render-components-end&gt;</a></span> [
+<span id="L64" class="LineNr"> 64 </span><span class="muRecipe">before</span> <span class="Constant"><a href='004-programming-environment.mu.html#L416'>&lt;render-components-end&gt;</a></span> [
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 <span id="L66" class="LineNr"> 66 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> recipe-errors
 <span id="L67" class="LineNr"> 67 </span>  <span class="Conceal">¦</span> error-index:num <span class="Special">&lt;-</span> get *env, <span class="Constant">error-index:offset</span>
@@ -166,7 +166,7 @@ if ('onhashchange' in window) {
 <span id="L103" class="LineNr">103 </span>]
 <span id="L104" class="LineNr">104 </span>
 <span id="L105" class="LineNr">105 </span><span class="Comment"># make sure we render any trace</span>
-<span id="L106" class="LineNr">106 </span><span class="muRecipe">after</span> <span class="Constant"><a href='010-sandbox-trace.mu.html#L249'>&lt;render-sandbox-trace-done&gt;</a></span> [
+<span id="L106" class="LineNr">106 </span><span class="muRecipe">after</span> <span class="Constant"><a href='010-sandbox-trace.mu.html#L251'>&lt;render-sandbox-trace-done&gt;</a></span> [
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 <span id="L108" class="LineNr">108 </span>  <span class="Conceal">¦</span> sandbox-errors:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">errors:offset</span>
 <span id="L109" class="LineNr">109 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-errors
@@ -189,7 +189,7 @@ if ('onhashchange' in window) {
 <span id="L126" class="LineNr">126 </span>  <span class="Conceal">¦</span> ]
 <span id="L127" class="LineNr">127 </span>  ]
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-<span id="L129" class="LineNr">129 </span>  <a href='004-programming-environment.mu.html#L383'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L121'>render</a>
+<span id="L129" class="LineNr">129 </span>  <a href='004-programming-environment.mu.html#L394'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
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 <span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
 <span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
diff --git a/html/edit/012-editor-undo.mu.html b/html/edit/012-editor-undo.mu.html
index 2c227c0f..490d67f9 100644
--- a/html/edit/012-editor-undo.mu.html
+++ b/html/edit/012-editor-undo.mu.html
@@ -165,7 +165,7 @@ if ('onhashchange' in window) {
 <span id="L102" class="LineNr"> 102 </span>  <span class="Constant">local-scope</span>
 <span id="L103" class="LineNr"> 103 </span>  <span class="Comment"># create an editor and type a character</span>
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-<span id="L105" class="LineNr"> 105 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L105" class="LineNr"> 105 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L108" class="LineNr"> 108 </span>  <span class="Conceal">¦</span> type <span class="Constant">[0]</span>
@@ -294,7 +294,7 @@ if ('onhashchange' in window) {
 <span id="L231" class="LineNr"> 231 </span>  <span class="Constant">local-scope</span>
 <span id="L232" class="LineNr"> 232 </span>  <span class="Comment"># create an editor and type multiple characters</span>
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-<span id="L234" class="LineNr"> 234 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L234" class="LineNr"> 234 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L237" class="LineNr"> 237 </span>  <span class="Conceal">¦</span> type <span class="Constant">[012]</span>
@@ -320,7 +320,7 @@ if ('onhashchange' in window) {
 <span id="L257" class="LineNr"> 257 </span>  <span class="Constant">local-scope</span>
 <span id="L258" class="LineNr"> 258 </span>  <span class="Comment"># create an editor with some text</span>
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-<span id="L260" class="LineNr"> 260 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[a]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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-<span id="L306" class="LineNr"> 306 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[  abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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@@ -542,7 +542,7 @@ if ('onhashchange' in window) {
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+<span id="L482" class="LineNr"> 482 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> contents, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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@@ -582,7 +582,7 @@ if ('onhashchange' in window) {
 <span id="L519" class="LineNr"> 519 </span>  <span class="Constant">local-scope</span>
 <span id="L520" class="LineNr"> 520 </span>  <span class="Comment"># create an editor</span>
 <span id="L521" class="LineNr"> 521 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L522" class="LineNr"> 522 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L522" class="LineNr"> 522 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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@@ -742,7 +742,7 @@ if ('onhashchange' in window) {
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+<span id="L682" class="LineNr"> 682 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> contents, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L684" class="LineNr"> 684 </span>  <span class="Comment"># move the cursor</span>
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@@ -834,7 +834,7 @@ if ('onhashchange' in window) {
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+<span id="L774" class="LineNr"> 774 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> contents, <span class="Constant">0/left</span>, <span class="Constant">5/right</span>
 <span id="L775" class="LineNr"> 775 </span>  <span class="Comment"># position cursor at end of screen and try to move right</span>
 <span id="L776" class="LineNr"> 776 </span>  assume-console [
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@@ -897,7 +897,7 @@ if ('onhashchange' in window) {
 <span id="L834" class="LineNr"> 834 </span>  contents:text <span class="Special">&lt;-</span> new <span class="Constant">[abc</span>
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+<span id="L837" class="LineNr"> 837 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> contents, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L838" class="LineNr"> 838 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
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@@ -942,7 +942,7 @@ if ('onhashchange' in window) {
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-<span id="L882" class="LineNr"> 882 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L50'>new-editor</a> contents, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L882" class="LineNr"> 882 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> contents, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
 <span id="L883" class="LineNr"> 883 </span>  <a href='002-typing.mu.html#L263'>editor-render</a> <a href='../081print.mu.html#L4'>screen</a>, e
 <span id="L884" class="LineNr"> 884 </span>  <span class="Comment"># move the cursor</span>
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@@ -993,7 +993,7 @@ if ('onhashchange' in window) {
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+<span id="L933" class="LineNr"> 933 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> contents, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
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 <span id="L935" class="LineNr"> 935 </span>  <span class="Comment"># move the cursor</span>
 <span id="L936" class="LineNr"> 936 </span>  assume-console [
@@ -1041,7 +1041,7 @@ if ('onhashchange' in window) {
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 <span id="L980" class="LineNr"> 980 </span><span class="Constant">f]</span>
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