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authorKartik K. Agaram <vc@akkartik.com>2017-03-07 01:41:48 -0800
committerKartik K. Agaram <vc@akkartik.com>2017-03-07 01:41:48 -0800
commit9e751bb8c0cdf771d34c839cb6591d892b8e62de (patch)
tree2ac86646cd0aa204626a4fc842dbe8b2aa526817 /html/edit/011-errors.mu.html
parent848ebc1e6335cd1a34e07662242a367fefbc5229 (diff)
downloadmu-9e751bb8c0cdf771d34c839cb6591d892b8e62de.tar.gz
3761
Diffstat (limited to 'html/edit/011-errors.mu.html')
-rw-r--r--html/edit/011-errors.mu.html757
1 files changed, 379 insertions, 378 deletions
diff --git a/html/edit/011-errors.mu.html b/html/edit/011-errors.mu.html
index c30f72a8..5a15e5ff 100644
--- a/html/edit/011-errors.mu.html
+++ b/html/edit/011-errors.mu.html
@@ -15,16 +15,17 @@ body { font-size: 12pt; font-family: monospace; color: #eeeeee; background-color
 a { text-decoration: none; }
 a:hover { text-decoration: underline; }
 * { font-size: 12pt; font-size: 1em; }
-.muData { color: #ffff00; }
-.muControl { color: #c0a020; }
+.muRecipe { color: #ff8700; }
+.muScenario { color: #00af00; }
 .Special { color: #c00000; }
+.Conceal { color: #4e4e4e; }
 .Delimiter { color: #800080; }
 .SalientComment { color: #00ffff; }
 .Constant { color: #00a0a0; }
 .LineNr { color: #444444; }
 .Comment { color: #9090ff; }
-.muRecipe { color: #ff8700; }
-.muScenario { color: #00af00; }
+.muControl { color: #c0a020; }
+.muData { color: #ffff00; }
 -->
 </style>
 
@@ -76,10 +77,10 @@ if ('onhashchange' in window) {
 <span id="L15" class="LineNr"> 15 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">recipe-errors:offset</span>, recipe-errors
 <span id="L16" class="LineNr"> 16 </span>  <span class="Comment"># if recipe editor has errors, stop</span>
 <span id="L17" class="LineNr"> 17 </span>  <span class="Delimiter">{</span>
-<span id="L18" class="LineNr"> 18 </span>    <span class="muControl">break-unless</span> recipe-errors
-<span id="L19" class="LineNr"> 19 </span>    <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
-<span id="L20" class="LineNr"> 20 </span>    errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
-<span id="L21" class="LineNr"> 21 </span>    <span class="muControl">return</span>
+<span id="L18" class="LineNr"> 18 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> recipe-errors
+<span id="L19" class="LineNr"> 19 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
+<span id="L20" class="LineNr"> 20 </span>  <span class="Conceal">¦</span> errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
+<span id="L21" class="LineNr"> 21 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
 <span id="L22" class="LineNr"> 22 </span>  <span class="Delimiter">}</span>
 <span id="L23" class="LineNr"> 23 </span>  errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
 <span id="L24" class="LineNr"> 24 </span>]
@@ -88,16 +89,16 @@ if ('onhashchange' in window) {
 <span id="L27" class="LineNr"> 27 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render status]</span>
 <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>
-<span id="L30" class="LineNr"> 30 </span>    <span class="muControl">break-unless</span> recipe-errors
-<span id="L31" class="LineNr"> 31 </span>    <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
+<span id="L30" class="LineNr"> 30 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> recipe-errors
+<span id="L31" class="LineNr"> 31 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
 <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#L488'>&lt;render-recipe-components-end&gt;</a></span> [
 <span id="L36" class="LineNr"> 36 </span>  <span class="Delimiter">{</span>
-<span id="L37" class="LineNr"> 37 </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="muControl">break-unless</span> recipe-errors
-<span id="L39" class="LineNr"> 39 </span>    row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, recipe-errors, left, right, <span class="Constant">1/red</span>, row
+<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
+<span id="L39" class="LineNr"> 39 </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#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, recipe-errors, left, right, <span class="Constant">1/red</span>, row
 <span id="L40" class="LineNr"> 40 </span>  <span class="Delimiter">}</span>
 <span id="L41" class="LineNr"> 41 </span>]
 <span id="L42" class="LineNr"> 42 </span>
@@ -115,22 +116,22 @@ if ('onhashchange' in window) {
 <span id="L54" class="LineNr"> 54 </span>
 <span id="L55" class="LineNr"> 55 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L183'>&lt;run-sandboxes-end&gt;</a></span> [
 <span id="L56" class="LineNr"> 56 </span>  <span class="Delimiter">{</span>
-<span id="L57" class="LineNr"> 57 </span>    error-index:num <span class="Special">&lt;-</span> get *env, <span class="Constant">error-index:offset</span>
-<span id="L58" class="LineNr"> 58 </span>    sandboxes-completed-successfully?:bool <span class="Special">&lt;-</span> equal error-index,<span class="Constant"> -1</span>
-<span id="L59" class="LineNr"> 59 </span>    <span class="muControl">break-if</span> sandboxes-completed-successfully?
-<span id="L60" class="LineNr"> 60 </span>    errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
+<span id="L57" class="LineNr"> 57 </span>  <span class="Conceal">¦</span> error-index:num <span class="Special">&lt;-</span> get *env, <span class="Constant">error-index:offset</span>
+<span id="L58" class="LineNr"> 58 </span>  <span class="Conceal">¦</span> sandboxes-completed-successfully?:bool <span class="Special">&lt;-</span> equal error-index,<span class="Constant"> -1</span>
+<span id="L59" class="LineNr"> 59 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandboxes-completed-successfully?
+<span id="L60" class="LineNr"> 60 </span>  <span class="Conceal">¦</span> errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
 <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#L467'>&lt;render-components-end&gt;</a></span> [
 <span id="L65" class="LineNr"> 65 </span>  <span class="Delimiter">{</span>
-<span id="L66" class="LineNr"> 66 </span>    <span class="muControl">break-if</span> recipe-errors
-<span id="L67" class="LineNr"> 67 </span>    error-index:num <span class="Special">&lt;-</span> get *env, <span class="Constant">error-index:offset</span>
-<span id="L68" class="LineNr"> 68 </span>    sandboxes-completed-successfully?:bool <span class="Special">&lt;-</span> equal error-index,<span class="Constant"> -1</span>
-<span id="L69" class="LineNr"> 69 </span>    <span class="muControl">break-if</span> sandboxes-completed-successfully?
-<span id="L70" class="LineNr"> 70 </span>    error-index-text:text <span class="Special">&lt;-</span> to-text error-index
-<span id="L71" class="LineNr"> 71 </span>    status:text <span class="Special">&lt;-</span> <a href='../061text.mu.html#L506'>interpolate</a> <span class="Constant">[errors found (_)    ]</span>, error-index-text
-<span id="L72" class="LineNr"> 72 </span>    <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, status, <span class="Constant">1/red</span>
+<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>
+<span id="L68" class="LineNr"> 68 </span>  <span class="Conceal">¦</span> sandboxes-completed-successfully?:bool <span class="Special">&lt;-</span> equal error-index,<span class="Constant"> -1</span>
+<span id="L69" class="LineNr"> 69 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandboxes-completed-successfully?
+<span id="L70" class="LineNr"> 70 </span>  <span class="Conceal">¦</span> error-index-text:text <span class="Special">&lt;-</span> to-text error-index
+<span id="L71" class="LineNr"> 71 </span>  <span class="Conceal">¦</span> status:text <span class="Special">&lt;-</span> <a href='../061text.mu.html#L506'>interpolate</a> <span class="Constant">[errors found (_)    ]</span>, error-index-text
+<span id="L72" class="LineNr"> 72 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, status, <span class="Constant">1/red</span>
 <span id="L73" class="LineNr"> 73 </span>  <span class="Delimiter">}</span>
 <span id="L74" class="LineNr"> 74 </span>]
 <span id="L75" class="LineNr"> 75 </span>
@@ -148,30 +149,30 @@ if ('onhashchange' in window) {
 <span id="L87" class="LineNr"> 87 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant"><a href='../081print.mu.html#L4'>screen</a>:offset</span>, fake-screen
 <span id="L88" class="LineNr"> 88 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">trace:offset</span>, trace
 <span id="L89" class="LineNr"> 89 </span>  <span class="Delimiter">{</span>
-<span id="L90" class="LineNr"> 90 </span>    <span class="muControl">break-if</span> errors
-<span id="L91" class="LineNr"> 91 </span>    <span class="muControl">break-if</span> completed?:bool
-<span id="L92" class="LineNr"> 92 </span>    errors <span class="Special">&lt;-</span> new <span class="Constant">[took too long!</span>
+<span id="L90" class="LineNr"> 90 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> errors
+<span id="L91" class="LineNr"> 91 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> completed?:bool
+<span id="L92" class="LineNr"> 92 </span>  <span class="Conceal">¦</span> errors <span class="Special">&lt;-</span> new <span class="Constant">[took too long!</span>
 <span id="L93" class="LineNr"> 93 </span><span class="Constant">]</span>
-<span id="L94" class="LineNr"> 94 </span>    *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">errors:offset</span>, errors
+<span id="L94" class="LineNr"> 94 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">errors:offset</span>, errors
 <span id="L95" class="LineNr"> 95 </span>  <span class="Delimiter">}</span>
 <span id="L96" class="LineNr"> 96 </span>  <span class="Delimiter">{</span>
-<span id="L97" class="LineNr"> 97 </span>    <span class="muControl">break-unless</span> errors
-<span id="L98" class="LineNr"> 98 </span>    error-index:num <span class="Special">&lt;-</span> get *env, <span class="Constant">error-index:offset</span>
-<span id="L99" class="LineNr"> 99 </span>    error-not-set?:bool <span class="Special">&lt;-</span> equal error-index,<span class="Constant"> -1</span>
-<span id="L100" class="LineNr">100 </span>    <span class="muControl">break-unless</span> error-not-set?
-<span id="L101" class="LineNr">101 </span>    *env <span class="Special">&lt;-</span> put *env, <span class="Constant">error-index:offset</span>, idx
+<span id="L97" class="LineNr"> 97 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> errors
+<span id="L98" class="LineNr"> 98 </span>  <span class="Conceal">¦</span> error-index:num <span class="Special">&lt;-</span> get *env, <span class="Constant">error-index:offset</span>
+<span id="L99" class="LineNr"> 99 </span>  <span class="Conceal">¦</span> error-not-set?:bool <span class="Special">&lt;-</span> equal error-index,<span class="Constant"> -1</span>
+<span id="L100" class="LineNr">100 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> error-not-set?
+<span id="L101" class="LineNr">101 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">error-index:offset</span>, idx
 <span id="L102" class="LineNr">102 </span>  <span class="Delimiter">}</span>
 <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#L252'>&lt;render-sandbox-trace-done&gt;</a></span> [
 <span id="L107" class="LineNr">107 </span>  <span class="Delimiter">{</span>
-<span id="L108" class="LineNr">108 </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="muControl">break-unless</span> sandbox-errors
-<span id="L110" class="LineNr">110 </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 class="Comment"># no response</span>
-<span id="L111" class="LineNr">111 </span>    row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-errors, left, right, <span class="Constant">1/red</span>, row
-<span id="L112" class="LineNr">112 </span>    <span class="Comment"># don't try to print anything more for this sandbox</span>
-<span id="L113" class="LineNr">113 </span>    <span class="muControl">jump</span> <span class="Constant">+render-sandbox-end</span>
+<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
+<span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</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 class="Comment"># no response</span>
+<span id="L111" class="LineNr">111 </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#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-errors, left, right, <span class="Constant">1/red</span>, row
+<span id="L112" class="LineNr">112 </span>  <span class="Conceal">¦</span> <span class="Comment"># don't try to print anything more for this sandbox</span>
+<span id="L113" class="LineNr">113 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+render-sandbox-end</span>
 <span id="L114" class="LineNr">114 </span>  <span class="Delimiter">}</span>
 <span id="L115" class="LineNr">115 </span>]
 <span id="L116" class="LineNr">116 </span>
@@ -180,51 +181,51 @@ if ('onhashchange' in window) {
 <span id="L119" class="LineNr">119 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
 <span id="L120" class="LineNr">120 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L121" class="LineNr">121 </span>  assume-resources [
-<span id="L122" class="LineNr">122 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L123" class="LineNr">123 </span>      <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L124" class="LineNr">124 </span><span class="Constant">      |  get 123:num, foo:offset|</span>
-<span id="L125" class="LineNr">125 </span><span class="Constant">      |]</span>|
-<span id="L126" class="LineNr">126 </span>    ]
+<span id="L122" class="LineNr">122 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L123" class="LineNr">123 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L124" class="LineNr">124 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  get 123:num, foo:offset|</span>
+<span id="L125" class="LineNr">125 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
+<span id="L126" class="LineNr">126 </span>  <span class="Conceal">¦</span> ]
 <span id="L127" class="LineNr">127 </span>  ]
 <span id="L128" class="LineNr">128 </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">[foo]</span>
 <span id="L129" class="LineNr">129 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L130" class="LineNr">130 </span>  screen-should-contain [
-<span id="L131" class="LineNr">131 </span>   <span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L132" class="LineNr">132 </span>   <span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
-<span id="L133" class="LineNr">133 </span>   <span class="Constant"> .  get 123:num, foo:offset                         ╎─────────────────────────────────────────────────.</span>
-<span id="L134" class="LineNr">134 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L135" class="LineNr">135 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L136" class="LineNr">136 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L137" class="LineNr">137 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<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>
+<span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span><span class="Constant"> .  get 123:num, foo:offset                         ╎─────────────────────────────────────────────────.</span>
+<span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎                                                 .</span>
+<span id="L135" class="LineNr">135 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L136" class="LineNr">136 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L137" class="LineNr">137 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L138" class="LineNr">138 </span>  ]
 <span id="L139" class="LineNr">139 </span>  assume-console [
-<span id="L140" class="LineNr">140 </span>    press F4
+<span id="L140" class="LineNr">140 </span>  <span class="Conceal">¦</span> press F4
 <span id="L141" class="LineNr">141 </span>  ]
 <span id="L142" class="LineNr">142 </span>  run [
-<span id="L143" class="LineNr">143 </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="L143" class="LineNr">143 </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="L144" class="LineNr">144 </span>  ]
 <span id="L145" class="LineNr">145 </span>  screen-should-contain [
-<span id="L146" class="LineNr">146 </span>   <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
-<span id="L147" class="LineNr">147 </span>   <span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
-<span id="L148" class="LineNr">148 </span>   <span class="Constant"> .  get 123:num, foo:offset                         ╎─────────────────────────────────────────────────.</span>
-<span id="L149" class="LineNr">149 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L150" class="LineNr">150 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L151" class="LineNr">151 </span>   <span class="Constant"> .foo: unknown element 'foo' in container 'number'  ╎                                                 .</span>
-<span id="L152" class="LineNr">152 </span>   <span class="Constant"> .foo: first ingredient of 'get' should be a contai↩╎                                                 .</span>
-<span id="L153" class="LineNr">153 </span>   <span class="Constant"> .ner, but got '123:num'                            ╎                                                 .</span>
-<span id="L154" class="LineNr">154 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L155" class="LineNr">155 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L146" class="LineNr">146 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                   run (F4)           .</span>
+<span id="L147" class="LineNr">147 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
+<span id="L148" class="LineNr">148 </span>  <span class="Conceal">¦</span><span class="Constant"> .  get 123:num, foo:offset                         ╎─────────────────────────────────────────────────.</span>
+<span id="L149" class="LineNr">149 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎                                                 .</span>
+<span id="L150" class="LineNr">150 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L151" class="LineNr">151 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: unknown element 'foo' in container 'number'  ╎                                                 .</span>
+<span id="L152" class="LineNr">152 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: first ingredient of 'get' should be a contai↩╎                                                 .</span>
+<span id="L153" class="LineNr">153 </span>  <span class="Conceal">¦</span><span class="Constant"> .ner, but got '123:num'                            ╎                                                 .</span>
+<span id="L154" class="LineNr">154 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L155" class="LineNr">155 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L156" class="LineNr">156 </span>  ]
 <span id="L157" class="LineNr">157 </span>  screen-should-contain-in-color <span class="Constant">1/red</span>, [
-<span id="L158" class="LineNr">158 </span>   <span class="Constant"> .  errors found                                                                                      .</span>
-<span id="L159" class="LineNr">159 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L160" class="LineNr">160 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L161" class="LineNr">161 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L162" class="LineNr">162 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L163" class="LineNr">163 </span>   <span class="Constant"> .foo: unknown element 'foo' in container 'number'                                                    .</span>
-<span id="L164" class="LineNr">164 </span>   <span class="Constant"> .foo: first ingredient of 'get' should be a contai                                                   .</span>
-<span id="L165" class="LineNr">165 </span>   <span class="Constant"> .ner, but got '123:num'                                                                              .</span>
-<span id="L166" class="LineNr">166 </span>   <span class="Constant"> .                                                                                                    .</span>
+<span id="L158" class="LineNr">158 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                                      .</span>
+<span id="L159" class="LineNr">159 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L160" class="LineNr">160 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L161" class="LineNr">161 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L162" class="LineNr">162 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L163" class="LineNr">163 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: unknown element 'foo' in container 'number'                                                    .</span>
+<span id="L164" class="LineNr">164 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: first ingredient of 'get' should be a contai                                                   .</span>
+<span id="L165" class="LineNr">165 </span>  <span class="Conceal">¦</span><span class="Constant"> .ner, but got '123:num'                                                                              .</span>
+<span id="L166" class="LineNr">166 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
 <span id="L167" class="LineNr">167 </span>  ]
 <span id="L168" class="LineNr">168 </span>]
 <span id="L169" class="LineNr">169 </span>
@@ -236,20 +237,20 @@ if ('onhashchange' in window) {
 <span id="L175" class="LineNr">175 </span>  ]
 <span id="L176" class="LineNr">176 </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="L177" class="LineNr">177 </span>  assume-console [
-<span id="L178" class="LineNr">178 </span>    left-click<span class="Constant"> 3</span>,<span class="Constant"> 80</span>
-<span id="L179" class="LineNr">179 </span>    <span class="Comment"># create invalid sandbox 1</span>
-<span id="L180" class="LineNr">180 </span>    type <span class="Constant">[get foo, x:offset]</span>
-<span id="L181" class="LineNr">181 </span>    press F4
-<span id="L182" class="LineNr">182 </span>    <span class="Comment"># create invalid sandbox 0</span>
-<span id="L183" class="LineNr">183 </span>    type <span class="Constant">[get foo, x:offset]</span>
-<span id="L184" class="LineNr">184 </span>    press F4
+<span id="L178" class="LineNr">178 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 80</span>
+<span id="L179" class="LineNr">179 </span>  <span class="Conceal">¦</span> <span class="Comment"># create invalid sandbox 1</span>
+<span id="L180" class="LineNr">180 </span>  <span class="Conceal">¦</span> type <span class="Constant">[get foo, x:offset]</span>
+<span id="L181" class="LineNr">181 </span>  <span class="Conceal">¦</span> press F4
+<span id="L182" class="LineNr">182 </span>  <span class="Conceal">¦</span> <span class="Comment"># create invalid sandbox 0</span>
+<span id="L183" class="LineNr">183 </span>  <span class="Conceal">¦</span> type <span class="Constant">[get foo, x:offset]</span>
+<span id="L184" class="LineNr">184 </span>  <span class="Conceal">¦</span> press F4
 <span id="L185" class="LineNr">185 </span>  ]
 <span id="L186" class="LineNr">186 </span>  run [
-<span id="L187" class="LineNr">187 </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="L187" class="LineNr">187 </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="L188" class="LineNr">188 </span>  ]
 <span id="L189" class="LineNr">189 </span>  <span class="Comment"># status line shows that error is in first sandbox</span>
 <span id="L190" class="LineNr">190 </span>  screen-should-contain [
-<span id="L191" class="LineNr">191 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L191" class="LineNr">191 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
 <span id="L192" class="LineNr">192 </span>  ]
 <span id="L193" class="LineNr">193 </span>]
 <span id="L194" class="LineNr">194 </span>
@@ -261,23 +262,23 @@ if ('onhashchange' in window) {
 <span id="L200" class="LineNr">200 </span>  ]
 <span id="L201" class="LineNr">201 </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="L202" class="LineNr">202 </span>  assume-console [
-<span id="L203" class="LineNr">203 </span>    left-click<span class="Constant"> 3</span>,<span class="Constant"> 80</span>
-<span id="L204" class="LineNr">204 </span>    <span class="Comment"># create invalid sandbox 2</span>
-<span id="L205" class="LineNr">205 </span>    type <span class="Constant">[get foo, x:offset]</span>
-<span id="L206" class="LineNr">206 </span>    press F4
-<span id="L207" class="LineNr">207 </span>    <span class="Comment"># create invalid sandbox 1</span>
-<span id="L208" class="LineNr">208 </span>    type <span class="Constant">[get foo, x:offset]</span>
-<span id="L209" class="LineNr">209 </span>    press F4
-<span id="L210" class="LineNr">210 </span>    <span class="Comment"># create valid sandbox 0</span>
-<span id="L211" class="LineNr">211 </span>    type <span class="Constant">[add 2, 2]</span>
-<span id="L212" class="LineNr">212 </span>    press F4
+<span id="L203" class="LineNr">203 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 80</span>
+<span id="L204" class="LineNr">204 </span>  <span class="Conceal">¦</span> <span class="Comment"># create invalid sandbox 2</span>
+<span id="L205" class="LineNr">205 </span>  <span class="Conceal">¦</span> type <span class="Constant">[get foo, x:offset]</span>
+<span id="L206" class="LineNr">206 </span>  <span class="Conceal">¦</span> press F4
+<span id="L207" class="LineNr">207 </span>  <span class="Conceal">¦</span> <span class="Comment"># create invalid sandbox 1</span>
+<span id="L208" class="LineNr">208 </span>  <span class="Conceal">¦</span> type <span class="Constant">[get foo, x:offset]</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> <span class="Comment"># create valid sandbox 0</span>
+<span id="L211" class="LineNr">211 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
+<span id="L212" class="LineNr">212 </span>  <span class="Conceal">¦</span> press F4
 <span id="L213" class="LineNr">213 </span>  ]
 <span id="L214" class="LineNr">214 </span>  run [
-<span id="L215" class="LineNr">215 </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>  <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="L216" class="LineNr">216 </span>  ]
 <span id="L217" class="LineNr">217 </span>  <span class="Comment"># status line shows that error is in second sandbox</span>
 <span id="L218" class="LineNr">218 </span>  screen-should-contain [
-<span id="L219" class="LineNr">219 </span>   <span class="Constant"> .  errors found (1)                                                               run (F4)           .</span>
+<span id="L219" class="LineNr">219 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (1)                                                               run (F4)           .</span>
 <span id="L220" class="LineNr">220 </span>  ]
 <span id="L221" class="LineNr">221 </span>]
 <span id="L222" class="LineNr">222 </span>
@@ -289,28 +290,28 @@ if ('onhashchange' in window) {
 <span id="L228" class="LineNr">228 </span>  ]
 <span id="L229" class="LineNr">229 </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">[get foo, x:offset]</span>  <span class="Comment"># invalid</span>
 <span id="L230" class="LineNr">230 </span>  assume-console [
-<span id="L231" class="LineNr">231 </span>    press F4  <span class="Comment"># generate error</span>
+<span id="L231" class="LineNr">231 </span>  <span class="Conceal">¦</span> press F4  <span class="Comment"># generate error</span>
 <span id="L232" class="LineNr">232 </span>  ]
 <span id="L233" class="LineNr">233 </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="L234" class="LineNr">234 </span>  assume-console [
-<span id="L235" class="LineNr">235 </span>    left-click<span class="Constant"> 3</span>,<span class="Constant"> 58</span>
-<span id="L236" class="LineNr">236 </span>    press ctrl-k
-<span id="L237" class="LineNr">237 </span>    type <span class="Constant">[add 2, 2]</span>  <span class="Comment"># valid code</span>
-<span id="L238" class="LineNr">238 </span>    press F4  <span class="Comment"># update sandbox</span>
+<span id="L235" class="LineNr">235 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 3</span>,<span class="Constant"> 58</span>
+<span id="L236" class="LineNr">236 </span>  <span class="Conceal">¦</span> press ctrl-k
+<span id="L237" class="LineNr">237 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>  <span class="Comment"># valid code</span>
+<span id="L238" class="LineNr">238 </span>  <span class="Conceal">¦</span> press F4  <span class="Comment"># update sandbox</span>
 <span id="L239" class="LineNr">239 </span>  ]
 <span id="L240" class="LineNr">240 </span>  run [
-<span id="L241" class="LineNr">241 </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="L241" class="LineNr">241 </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="L242" class="LineNr">242 </span>  ]
 <span id="L243" class="LineNr">243 </span>  <span class="Comment"># error should disappear</span>
 <span id="L244" class="LineNr">244 </span>  screen-should-contain [
-<span id="L245" class="LineNr">245 </span>   <span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L246" class="LineNr">246 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L247" class="LineNr">247 </span><span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L248" class="LineNr">248 </span>   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L249" class="LineNr">249 </span>   <span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L250" class="LineNr">250 </span>   <span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L251" class="LineNr">251 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L252" class="LineNr">252 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L245" class="LineNr">245 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L247" class="LineNr">247 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L248" class="LineNr">248 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L250" class="LineNr">250 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L251" class="LineNr">251 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L252" class="LineNr">252 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L253" class="LineNr">253 </span>  ]
 <span id="L254" class="LineNr">254 </span>]
 <span id="L255" class="LineNr">255 </span>
@@ -320,51 +321,51 @@ if ('onhashchange' in window) {
 <span id="L259" class="LineNr">259 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L260" class="LineNr">260 </span>  <span class="Comment"># define a shape-shifting recipe with an error</span>
 <span id="L261" class="LineNr">261 </span>  assume-resources [
-<span id="L262" class="LineNr">262 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L263" class="LineNr">263 </span>      <span class="Constant">|recipe</span> foo x:_elem<span class="muRecipe"> -&gt; </span>z:_elem <span class="Constant">[|</span>
-<span id="L264" class="LineNr">264 </span><span class="Constant">      |  local-scope|</span>
-<span id="L265" class="LineNr">265 </span><span class="Constant">      |  load-ingredients|</span>
-<span id="L266" class="LineNr">266 </span><span class="Constant">      |  y:&amp;:num &lt;- copy 0|</span>
-<span id="L267" class="LineNr">267 </span><span class="Constant">      |  z &lt;- add x, y|</span>
-<span id="L268" class="LineNr">268 </span><span class="Constant">      |]</span>|
-<span id="L269" class="LineNr">269 </span>    ]
+<span id="L262" class="LineNr">262 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L263" class="LineNr">263 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo x:_elem<span class="muRecipe"> -&gt; </span>z:_elem <span class="Constant">[|</span>
+<span id="L264" class="LineNr">264 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  local-scope|</span>
+<span id="L265" class="LineNr">265 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  load-ingredients|</span>
+<span id="L266" class="LineNr">266 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  y:&amp;:num &lt;- copy 0|</span>
+<span id="L267" class="LineNr">267 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  z &lt;- add x, y|</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"> |]</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">[foo 2]</span>
 <span id="L272" class="LineNr">272 </span>  assume-console [
-<span id="L273" class="LineNr">273 </span>    press F4
+<span id="L273" class="LineNr">273 </span>  <span class="Conceal">¦</span> press F4
 <span id="L274" class="LineNr">274 </span>  ]
 <span id="L275" class="LineNr">275 </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="L276" class="LineNr">276 </span>  screen-should-contain [
-<span id="L277" class="LineNr">277 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
-<span id="L278" class="LineNr">278 </span>   <span class="Constant"> .recipe foo x:_elem -&gt; z:_elem [                   ╎                                                 .</span>
-<span id="L279" class="LineNr">279 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L280" class="LineNr">280 </span>   <span class="Constant"> .  load-ingredients                                ╎0   edit          copy            delete         .</span>
-<span id="L281" class="LineNr">281 </span>   <span class="Constant"> .  y:&amp;:num &lt;- copy 0                               ╎foo 2                                            .</span>
-<span id="L282" class="LineNr">282 </span>   <span class="Constant"> .  z &lt;- add x, y                                   ╎foo_2: 'add' requires number ingredients, but go↩.</span>
-<span id="L283" class="LineNr">283 </span>   <span class="Constant"> .]                                                 ╎t 'y'                                            .</span>
-<span id="L284" class="LineNr">284 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L285" class="LineNr">285 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L286" class="LineNr">286 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L277" class="LineNr">277 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L278" class="LineNr">278 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo x:_elem -&gt; z:_elem [                   ╎                                                 .</span>
+<span id="L279" class="LineNr">279 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L280" class="LineNr">280 </span>  <span class="Conceal">¦</span><span class="Constant"> .  load-ingredients                                ╎0   edit          copy            delete         .</span>
+<span id="L281" class="LineNr">281 </span>  <span class="Conceal">¦</span><span class="Constant"> .  y:&amp;:num &lt;- copy 0                               ╎foo 2                                            .</span>
+<span id="L282" class="LineNr">282 </span>  <span class="Conceal">¦</span><span class="Constant"> .  z &lt;- add x, y                                   ╎foo_2: 'add' requires number ingredients, but go↩.</span>
+<span id="L283" class="LineNr">283 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎t 'y'                                            .</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="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L286" class="LineNr">286 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L287" class="LineNr">287 </span>  ]
 <span id="L288" class="LineNr">288 </span>  <span class="Comment"># now rerun everything</span>
 <span id="L289" class="LineNr">289 </span>  assume-console [
-<span id="L290" class="LineNr">290 </span>    press F4
+<span id="L290" class="LineNr">290 </span>  <span class="Conceal">¦</span> press F4
 <span id="L291" class="LineNr">291 </span>  ]
 <span id="L292" class="LineNr">292 </span>  run [
-<span id="L293" class="LineNr">293 </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="L293" class="LineNr">293 </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="L294" class="LineNr">294 </span>  ]
 <span id="L295" class="LineNr">295 </span>  <span class="Comment"># error should remain unchanged</span>
 <span id="L296" class="LineNr">296 </span>  screen-should-contain [
-<span id="L297" class="LineNr">297 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
-<span id="L298" class="LineNr">298 </span>   <span class="Constant"> .recipe foo x:_elem -&gt; z:_elem [                   ╎                                                 .</span>
-<span id="L299" class="LineNr">299 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L300" class="LineNr">300 </span>   <span class="Constant"> .  load-ingredients                                ╎0   edit          copy            delete         .</span>
-<span id="L301" class="LineNr">301 </span>   <span class="Constant"> .  y:&amp;:num &lt;- copy 0                               ╎foo 2                                            .</span>
-<span id="L302" class="LineNr">302 </span>   <span class="Constant"> .  z &lt;- add x, y                                   ╎foo_3: 'add' requires number ingredients, but go↩.</span>
-<span id="L303" class="LineNr">303 </span>   <span class="Constant"> .]                                                 ╎t 'y'                                            .</span>
-<span id="L304" class="LineNr">304 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L305" class="LineNr">305 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L306" class="LineNr">306 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L297" class="LineNr">297 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L298" class="LineNr">298 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo x:_elem -&gt; z:_elem [                   ╎                                                 .</span>
+<span id="L299" class="LineNr">299 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L300" class="LineNr">300 </span>  <span class="Conceal">¦</span><span class="Constant"> .  load-ingredients                                ╎0   edit          copy            delete         .</span>
+<span id="L301" class="LineNr">301 </span>  <span class="Conceal">¦</span><span class="Constant"> .  y:&amp;:num &lt;- copy 0                               ╎foo 2                                            .</span>
+<span id="L302" class="LineNr">302 </span>  <span class="Conceal">¦</span><span class="Constant"> .  z &lt;- add x, y                                   ╎foo_3: 'add' requires number ingredients, but go↩.</span>
+<span id="L303" class="LineNr">303 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎t 'y'                                            .</span>
+<span id="L304" class="LineNr">304 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L305" class="LineNr">305 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L306" class="LineNr">306 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L307" class="LineNr">307 </span>  ]
 <span id="L308" class="LineNr">308 </span>]
 <span id="L309" class="LineNr">309 </span>
@@ -374,10 +375,10 @@ if ('onhashchange' in window) {
 <span id="L313" class="LineNr">313 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L314" class="LineNr">314 </span>  <span class="Comment"># overload a well-known shape-shifting recipe</span>
 <span id="L315" class="LineNr">315 </span>  assume-resources [
-<span id="L316" class="LineNr">316 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L317" class="LineNr">317 </span>      <span class="Constant">|recipe</span> length l:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>n:num <span class="Constant">[|</span>
-<span id="L318" class="LineNr">318 </span><span class="Constant">      |]</span>|
-<span id="L319" class="LineNr">319 </span>    ]
+<span id="L316" class="LineNr">316 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L317" class="LineNr">317 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> length l:&amp;:list:_elem<span class="muRecipe"> -&gt; </span>n:num <span class="Constant">[|</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"> |]</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>  <span class="Comment"># call code that uses other variants of it, but not it itself</span>
 <span id="L322" class="LineNr">322 </span>  test-sandbox:text <span class="Special">&lt;-</span> new <span class="Constant">[x:&amp;:list:num &lt;- copy 0</span>
@@ -385,51 +386,51 @@ if ('onhashchange' in window) {
 <span id="L324" class="LineNr">324 </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
 <span id="L325" class="LineNr">325 </span>  <span class="Comment"># run it once</span>
 <span id="L326" class="LineNr">326 </span>  assume-console [
-<span id="L327" class="LineNr">327 </span>    press F4
+<span id="L327" class="LineNr">327 </span>  <span class="Conceal">¦</span> press F4
 <span id="L328" class="LineNr">328 </span>  ]
 <span id="L329" class="LineNr">329 </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 class="Comment"># no errors anywhere on screen (can't check anything else, since to-text will return an address)</span>
 <span id="L331" class="LineNr">331 </span>  screen-should-contain-in-color <span class="Constant">1/red</span>, [
-<span id="L332" class="LineNr">332 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L333" class="LineNr">333 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L334" class="LineNr">334 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L335" class="LineNr">335 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L336" class="LineNr">336 </span>   <span class="Constant"> .                                                                &lt;-                                  .</span>
-<span id="L337" class="LineNr">337 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L338" class="LineNr">338 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L339" class="LineNr">339 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L340" class="LineNr">340 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L341" class="LineNr">341 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L342" class="LineNr">342 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L343" class="LineNr">343 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L344" class="LineNr">344 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L345" class="LineNr">345 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L346" class="LineNr">346 </span>   <span class="Constant"> .                                                                                                    .</span>
+<span id="L332" class="LineNr">332 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L333" class="LineNr">333 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</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"> .                                                                &lt;-                                  .</span>
+<span id="L337" class="LineNr">337 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</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 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 class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L344" class="LineNr">344 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</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 class="Comment"># rerun everything</span>
 <span id="L349" class="LineNr">349 </span>  assume-console [
-<span id="L350" class="LineNr">350 </span>    press F4
+<span id="L350" class="LineNr">350 </span>  <span class="Conceal">¦</span> press F4
 <span id="L351" class="LineNr">351 </span>  ]
 <span id="L352" class="LineNr">352 </span>  run [
-<span id="L353" class="LineNr">353 </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="L353" class="LineNr">353 </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="L354" class="LineNr">354 </span>  ]
 <span id="L355" class="LineNr">355 </span>  <span class="Comment"># still no errors</span>
 <span id="L356" class="LineNr">356 </span>  screen-should-contain-in-color <span class="Constant">1/red</span>, [
-<span id="L357" class="LineNr">357 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L358" class="LineNr">358 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L359" class="LineNr">359 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L360" class="LineNr">360 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L361" class="LineNr">361 </span>   <span class="Constant"> .                                                                &lt;-                                  .</span>
-<span id="L362" class="LineNr">362 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L363" class="LineNr">363 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L364" class="LineNr">364 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L365" class="LineNr">365 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L366" class="LineNr">366 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L367" class="LineNr">367 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L368" class="LineNr">368 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L369" class="LineNr">369 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L370" class="LineNr">370 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L371" class="LineNr">371 </span>   <span class="Constant"> .                                                                                                    .</span>
+<span id="L357" class="LineNr">357 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L358" class="LineNr">358 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L359" class="LineNr">359 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<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"> .                                                                &lt;-                                  .</span>
+<span id="L362" class="LineNr">362 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</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 class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L366" class="LineNr">366 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L367" class="LineNr">367 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L368" class="LineNr">368 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L369" class="LineNr">369 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L370" class="LineNr">370 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L371" class="LineNr">371 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
 <span id="L372" class="LineNr">372 </span>  ]
 <span id="L373" class="LineNr">373 </span>]
 <span id="L374" class="LineNr">374 </span>
@@ -438,29 +439,29 @@ if ('onhashchange' in window) {
 <span id="L377" class="LineNr">377 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
 <span id="L378" class="LineNr">378 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L379" class="LineNr">379 </span>  assume-resources [
-<span id="L380" class="LineNr">380 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L381" class="LineNr">381 </span>      <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L382" class="LineNr">382 </span><span class="Constant">      |  x &lt;- copy 0|</span>
-<span id="L383" class="LineNr">383 </span><span class="Constant">      |]</span>|
-<span id="L384" class="LineNr">384 </span>    ]
+<span id="L380" class="LineNr">380 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L381" class="LineNr">381 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L382" class="LineNr">382 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  x &lt;- copy 0|</span>
+<span id="L383" class="LineNr">383 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
+<span id="L384" class="LineNr">384 </span>  <span class="Conceal">¦</span> ]
 <span id="L385" class="LineNr">385 </span>  ]
 <span id="L386" class="LineNr">386 </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">[foo]</span>
 <span id="L387" class="LineNr">387 </span>  assume-console [
-<span id="L388" class="LineNr">388 </span>    press F4
+<span id="L388" class="LineNr">388 </span>  <span class="Conceal">¦</span> press F4
 <span id="L389" class="LineNr">389 </span>  ]
 <span id="L390" class="LineNr">390 </span>  run [
-<span id="L391" class="LineNr">391 </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="L391" class="LineNr">391 </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="L392" class="LineNr">392 </span>  ]
 <span id="L393" class="LineNr">393 </span>  screen-should-contain [
-<span id="L394" class="LineNr">394 </span>   <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
-<span id="L395" class="LineNr">395 </span>   <span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
-<span id="L396" class="LineNr">396 </span>   <span class="Constant"> .  x &lt;- copy 0                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L397" class="LineNr">397 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L398" class="LineNr">398 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L399" class="LineNr">399 </span>   <span class="Constant"> .foo: missing type for 'x' in 'x &lt;- copy 0'        ╎                                                 .</span>
-<span id="L400" class="LineNr">400 </span>   <span class="Constant"> .foo: can't copy '0' to 'x'; types don't match     ╎                                                 .</span>
-<span id="L401" class="LineNr">401 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L402" class="LineNr">402 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L394" class="LineNr">394 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                   run (F4)           .</span>
+<span id="L395" class="LineNr">395 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
+<span id="L396" class="LineNr">396 </span>  <span class="Conceal">¦</span><span class="Constant"> .  x &lt;- copy 0                                     ╎─────────────────────────────────────────────────.</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"> .                                                  ╎                                                 .</span>
+<span id="L399" class="LineNr">399 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: missing type for 'x' in 'x &lt;- copy 0'        ╎                                                 .</span>
+<span id="L400" class="LineNr">400 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: can't copy '0' to 'x'; types don't match     ╎                                                 .</span>
+<span id="L401" class="LineNr">401 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L402" class="LineNr">402 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L403" class="LineNr">403 </span>  ]
 <span id="L404" class="LineNr">404 </span>]
 <span id="L405" class="LineNr">405 </span>
@@ -470,26 +471,26 @@ if ('onhashchange' in window) {
 <span id="L409" class="LineNr">409 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L410" class="LineNr">410 </span>  <span class="Comment"># recipe is incomplete (unbalanced '[')</span>
 <span id="L411" class="LineNr">411 </span>  assume-resources [
-<span id="L412" class="LineNr">412 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L413" class="LineNr">413 </span>      <span class="Constant">|recipe</span> foo \\\<span class="Constant">[|</span>
-<span id="L414" class="LineNr">414 </span><span class="Constant">      |  x &lt;- copy 0|</span>
-<span id="L415" class="LineNr">415 </span><span class="Constant">    ]</span>
+<span id="L412" class="LineNr">412 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L413" class="LineNr">413 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo \\\<span class="Constant">[|</span>
+<span id="L414" class="LineNr">414 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  x &lt;- copy 0|</span>
+<span id="L415" class="LineNr">415 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> ]</span>
 <span id="L416" class="LineNr">416 </span>  ]
 <span id="L417" class="LineNr">417 </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">[foo]</span>
 <span id="L418" class="LineNr">418 </span>  assume-console [
-<span id="L419" class="LineNr">419 </span>    press F4
+<span id="L419" class="LineNr">419 </span>  <span class="Conceal">¦</span> press F4
 <span id="L420" class="LineNr">420 </span>  ]
 <span id="L421" class="LineNr">421 </span>  run [
-<span id="L422" class="LineNr">422 </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="L422" class="LineNr">422 </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="L423" class="LineNr">423 </span>  ]
 <span id="L424" class="LineNr">424 </span>  screen-should-contain [
-<span id="L425" class="LineNr">425 </span>   <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
-<span id="L426" class="LineNr">426 </span>   <span class="Constant"> .recipe foo \\[                                      ╎foo                                              .</span>
-<span id="L427" class="LineNr">427 </span>   <span class="Constant"> .  x &lt;- copy 0                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L428" class="LineNr">428 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L429" class="LineNr">429 </span>   <span class="Constant"> .9: unbalanced '\\[' for recipe                      ╎                                                 .</span>
-<span id="L430" class="LineNr">430 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L431" class="LineNr">431 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L425" class="LineNr">425 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                   run (F4)           .</span>
+<span id="L426" class="LineNr">426 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo \\[                                      ╎foo                                              .</span>
+<span id="L427" class="LineNr">427 </span>  <span class="Conceal">¦</span><span class="Constant"> .  x &lt;- copy 0                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L428" class="LineNr">428 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L429" class="LineNr">429 </span>  <span class="Conceal">¦</span><span class="Constant"> .9: unbalanced '\\[' for recipe                      ╎                                                 .</span>
+<span id="L430" class="LineNr">430 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L431" class="LineNr">431 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L432" class="LineNr">432 </span>  ]
 <span id="L433" class="LineNr">433 </span>]
 <span id="L434" class="LineNr">434 </span>
@@ -498,33 +499,33 @@ if ('onhashchange' in window) {
 <span id="L437" class="LineNr">437 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
 <span id="L438" class="LineNr">438 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L439" class="LineNr">439 </span>  assume-resources [
-<span id="L440" class="LineNr">440 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L441" class="LineNr">441 </span>      <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L442" class="LineNr">442 </span><span class="Constant">      |  local-scope|</span>
-<span id="L443" class="LineNr">443 </span><span class="Constant">      |  x:&amp;:point &lt;- new point:type|</span>
-<span id="L444" class="LineNr">444 </span><span class="Constant">      |  get x:&amp;:point, 1:offset|</span>
-<span id="L445" class="LineNr">445 </span><span class="Constant">      |]</span>|
-<span id="L446" class="LineNr">446 </span>    ]
+<span id="L440" class="LineNr">440 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L441" class="LineNr">441 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L442" class="LineNr">442 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  local-scope|</span>
+<span id="L443" class="LineNr">443 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  x:&amp;:point &lt;- new point:type|</span>
+<span id="L444" class="LineNr">444 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  get x:&amp;:point, 1:offset|</span>
+<span id="L445" class="LineNr">445 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
+<span id="L446" class="LineNr">446 </span>  <span class="Conceal">¦</span> ]
 <span id="L447" class="LineNr">447 </span>  ]
 <span id="L448" class="LineNr">448 </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">[foo]</span>
 <span id="L449" class="LineNr">449 </span>  assume-console [
-<span id="L450" class="LineNr">450 </span>    press F4
+<span id="L450" class="LineNr">450 </span>  <span class="Conceal">¦</span> press F4
 <span id="L451" class="LineNr">451 </span>  ]
 <span id="L452" class="LineNr">452 </span>  run [
-<span id="L453" class="LineNr">453 </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="L453" class="LineNr">453 </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="L454" class="LineNr">454 </span>  ]
 <span id="L455" class="LineNr">455 </span>  screen-should-contain [
-<span id="L456" class="LineNr">456 </span>   <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
-<span id="L457" class="LineNr">457 </span>   <span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
-<span id="L458" class="LineNr">458 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L459" class="LineNr">459 </span>   <span class="Constant"> .  x:&amp;:point &lt;- new point:type                     ╎                                                 .</span>
-<span id="L460" class="LineNr">460 </span>   <span class="Constant"> .  get x:&amp;:point, 1:offset                         ╎                                                 .</span>
-<span id="L461" class="LineNr">461 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L462" class="LineNr">462 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L463" class="LineNr">463 </span>   <span class="Constant"> .foo: first ingredient of 'get' should be a contai↩╎                                                 .</span>
-<span id="L464" class="LineNr">464 </span>   <span class="Constant"> .ner, but got 'x:&amp;:point'                          ╎                                                 .</span>
-<span id="L465" class="LineNr">465 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L466" class="LineNr">466 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L456" class="LineNr">456 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                   run (F4)           .</span>
+<span id="L457" class="LineNr">457 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
+<span id="L458" class="LineNr">458 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L459" class="LineNr">459 </span>  <span class="Conceal">¦</span><span class="Constant"> .  x:&amp;:point &lt;- new point:type                     ╎                                                 .</span>
+<span id="L460" class="LineNr">460 </span>  <span class="Conceal">¦</span><span class="Constant"> .  get x:&amp;:point, 1:offset                         ╎                                                 .</span>
+<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"> .                                                  ╎                                                 .</span>
+<span id="L463" class="LineNr">463 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: first ingredient of 'get' should be a contai↩╎                                                 .</span>
+<span id="L464" class="LineNr">464 </span>  <span class="Conceal">¦</span><span class="Constant"> .ner, but got 'x:&amp;:point'                          ╎                                                 .</span>
+<span id="L465" class="LineNr">465 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L466" class="LineNr">466 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L467" class="LineNr">467 </span>  ]
 <span id="L468" class="LineNr">468 </span>]
 <span id="L469" class="LineNr">469 </span>
@@ -533,35 +534,35 @@ if ('onhashchange' in window) {
 <span id="L472" class="LineNr">472 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
 <span id="L473" class="LineNr">473 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L474" class="LineNr">474 </span>  assume-resources [
-<span id="L475" class="LineNr">475 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L476" class="LineNr">476 </span>      <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L477" class="LineNr">477 </span><span class="Constant">      |  local-scope|</span>
-<span id="L478" class="LineNr">478 </span><span class="Constant">      |  x:num &lt;- copy 0|</span>
-<span id="L479" class="LineNr">479 </span><span class="Constant">      |  y:&amp;:point &lt;- new point:type|</span>
-<span id="L480" class="LineNr">480 </span><span class="Constant">      |  get *y:&amp;:point, x:num|</span>
-<span id="L481" class="LineNr">481 </span><span class="Constant">      |]</span>|
-<span id="L482" class="LineNr">482 </span>    ]
+<span id="L475" class="LineNr">475 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L476" class="LineNr">476 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L477" class="LineNr">477 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  local-scope|</span>
+<span id="L478" class="LineNr">478 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  x:num &lt;- copy 0|</span>
+<span id="L479" class="LineNr">479 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  y:&amp;:point &lt;- new point:type|</span>
+<span id="L480" class="LineNr">480 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  get *y:&amp;:point, x:num|</span>
+<span id="L481" class="LineNr">481 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
+<span id="L482" class="LineNr">482 </span>  <span class="Conceal">¦</span> ]
 <span id="L483" class="LineNr">483 </span>  ]
 <span id="L484" class="LineNr">484 </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">[foo]</span>
 <span id="L485" class="LineNr">485 </span>  assume-console [
-<span id="L486" class="LineNr">486 </span>    press F4
+<span id="L486" class="LineNr">486 </span>  <span class="Conceal">¦</span> press F4
 <span id="L487" class="LineNr">487 </span>  ]
 <span id="L488" class="LineNr">488 </span>  run [
-<span id="L489" class="LineNr">489 </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="L489" class="LineNr">489 </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="L490" class="LineNr">490 </span>  ]
 <span id="L491" class="LineNr">491 </span>  screen-should-contain [
-<span id="L492" class="LineNr">492 </span>   <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
-<span id="L493" class="LineNr">493 </span>   <span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
-<span id="L494" class="LineNr">494 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L495" class="LineNr">495 </span>   <span class="Constant"> .  x:num &lt;- copy 0                                 ╎                                                 .</span>
-<span id="L496" class="LineNr">496 </span>   <span class="Constant"> .  y:&amp;:point &lt;- new point:type                     ╎                                                 .</span>
-<span id="L497" class="LineNr">497 </span>   <span class="Constant"> .  get *y:&amp;:point, x:num                           ╎                                                 .</span>
-<span id="L498" class="LineNr">498 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L499" class="LineNr">499 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L500" class="LineNr">500 </span>   <span class="Constant"> .foo: second ingredient of 'get' should have type ↩╎                                                 .</span>
-<span id="L501" class="LineNr">501 </span>   <span class="Constant"> .'offset', but got 'x:num'                         ╎                                                 .</span>
-<span id="L502" class="LineNr">502 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L503" class="LineNr">503 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L492" class="LineNr">492 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                   run (F4)           .</span>
+<span id="L493" class="LineNr">493 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
+<span id="L494" class="LineNr">494 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L495" class="LineNr">495 </span>  <span class="Conceal">¦</span><span class="Constant"> .  x:num &lt;- copy 0                                 ╎                                                 .</span>
+<span id="L496" class="LineNr">496 </span>  <span class="Conceal">¦</span><span class="Constant"> .  y:&amp;:point &lt;- new point:type                     ╎                                                 .</span>
+<span id="L497" class="LineNr">497 </span>  <span class="Conceal">¦</span><span class="Constant"> .  get *y:&amp;:point, x:num                           ╎                                                 .</span>
+<span id="L498" class="LineNr">498 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎                                                 .</span>
+<span id="L499" class="LineNr">499 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L500" class="LineNr">500 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: second ingredient of 'get' should have type ↩╎                                                 .</span>
+<span id="L501" class="LineNr">501 </span>  <span class="Conceal">¦</span><span class="Constant"> .'offset', but got 'x:num'                         ╎                                                 .</span>
+<span id="L502" class="LineNr">502 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L503" class="LineNr">503 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L504" class="LineNr">504 </span>  ]
 <span id="L505" class="LineNr">505 </span>]
 <span id="L506" class="LineNr">506 </span>
@@ -571,48 +572,48 @@ if ('onhashchange' in window) {
 <span id="L510" class="LineNr">510 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">15/height</span>
 <span id="L511" class="LineNr">511 </span>  <span class="Comment"># try to run a file with an error</span>
 <span id="L512" class="LineNr">512 </span>  assume-resources [
-<span id="L513" class="LineNr">513 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L514" class="LineNr">514 </span>      <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L515" class="LineNr">515 </span><span class="Constant">      |  local-scope|</span>
-<span id="L516" class="LineNr">516 </span><span class="Constant">      |  x:num &lt;- copy y:num|</span>
-<span id="L517" class="LineNr">517 </span><span class="Constant">      |]</span>|
-<span id="L518" class="LineNr">518 </span>    ]
+<span id="L513" class="LineNr">513 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L514" class="LineNr">514 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L515" class="LineNr">515 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  local-scope|</span>
+<span id="L516" class="LineNr">516 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  x:num &lt;- copy y:num|</span>
+<span id="L517" class="LineNr">517 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
+<span id="L518" class="LineNr">518 </span>  <span class="Conceal">¦</span> ]
 <span id="L519" class="LineNr">519 </span>  ]
 <span id="L520" class="LineNr">520 </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">[foo]</span>
 <span id="L521" class="LineNr">521 </span>  assume-console [
-<span id="L522" class="LineNr">522 </span>    press F4
+<span id="L522" class="LineNr">522 </span>  <span class="Conceal">¦</span> press F4
 <span id="L523" class="LineNr">523 </span>  ]
 <span id="L524" class="LineNr">524 </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="L525" class="LineNr">525 </span>  screen-should-contain [
-<span id="L526" class="LineNr">526 </span>   <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
-<span id="L527" class="LineNr">527 </span>   <span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
-<span id="L528" class="LineNr">528 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L529" class="LineNr">529 </span>   <span class="Constant"> .  x:num &lt;- copy y:num                             ╎                                                 .</span>
-<span id="L530" class="LineNr">530 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L531" class="LineNr">531 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L532" class="LineNr">532 </span>   <span class="Constant"> .foo: tried to read ingredient 'y' in 'x:num &lt;- co↩╎                                                 .</span>
-<span id="L533" class="LineNr">533 </span>   <span class="Constant"> .py y:num' but it hasn't been written to yet       ╎                                                 .</span>
-<span id="L534" class="LineNr">534 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L535" class="LineNr">535 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L526" class="LineNr">526 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                   run (F4)           .</span>
+<span id="L527" class="LineNr">527 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
+<span id="L528" class="LineNr">528 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L529" class="LineNr">529 </span>  <span class="Conceal">¦</span><span class="Constant"> .  x:num &lt;- copy y:num                             ╎                                                 .</span>
+<span id="L530" class="LineNr">530 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎                                                 .</span>
+<span id="L531" class="LineNr">531 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L532" class="LineNr">532 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: tried to read ingredient 'y' in 'x:num &lt;- co↩╎                                                 .</span>
+<span id="L533" class="LineNr">533 </span>  <span class="Conceal">¦</span><span class="Constant"> .py y:num' but it hasn't been written to yet       ╎                                                 .</span>
+<span id="L534" class="LineNr">534 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L535" class="LineNr">535 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L536" class="LineNr">536 </span>  ]
 <span id="L537" class="LineNr">537 </span>  <span class="Comment"># rerun the file, check for the same error</span>
 <span id="L538" class="LineNr">538 </span>  assume-console [
-<span id="L539" class="LineNr">539 </span>    press F4
+<span id="L539" class="LineNr">539 </span>  <span class="Conceal">¦</span> press F4
 <span id="L540" class="LineNr">540 </span>  ]
 <span id="L541" class="LineNr">541 </span>  run [
-<span id="L542" class="LineNr">542 </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="L542" class="LineNr">542 </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="L543" class="LineNr">543 </span>  ]
 <span id="L544" class="LineNr">544 </span>  screen-should-contain [
-<span id="L545" class="LineNr">545 </span>   <span class="Constant"> .  errors found                                                                   run (F4)           .</span>
-<span id="L546" class="LineNr">546 </span>   <span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
-<span id="L547" class="LineNr">547 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L548" class="LineNr">548 </span>   <span class="Constant"> .  x:num &lt;- copy y:num                             ╎                                                 .</span>
-<span id="L549" class="LineNr">549 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L550" class="LineNr">550 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L551" class="LineNr">551 </span>   <span class="Constant"> .foo: tried to read ingredient 'y' in 'x:num &lt;- co↩╎                                                 .</span>
-<span id="L552" class="LineNr">552 </span>   <span class="Constant"> .py y:num' but it hasn't been written to yet       ╎                                                 .</span>
-<span id="L553" class="LineNr">553 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L554" class="LineNr">554 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L545" class="LineNr">545 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found                                                                   run (F4)           .</span>
+<span id="L546" class="LineNr">546 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎foo                                              .</span>
+<span id="L547" class="LineNr">547 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L548" class="LineNr">548 </span>  <span class="Conceal">¦</span><span class="Constant"> .  x:num &lt;- copy y:num                             ╎                                                 .</span>
+<span id="L549" class="LineNr">549 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎                                                 .</span>
+<span id="L550" class="LineNr">550 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L551" class="LineNr">551 </span>  <span class="Conceal">¦</span><span class="Constant"> .foo: tried to read ingredient 'y' in 'x:num &lt;- co↩╎                                                 .</span>
+<span id="L552" class="LineNr">552 </span>  <span class="Conceal">¦</span><span class="Constant"> .py y:num' but it hasn't been written to yet       ╎                                                 .</span>
+<span id="L553" class="LineNr">553 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L554" class="LineNr">554 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L555" class="LineNr">555 </span>  ]
 <span id="L556" class="LineNr">556 </span>]
 <span id="L557" class="LineNr">557 </span>
@@ -625,56 +626,56 @@ if ('onhashchange' in window) {
 <span id="L564" class="LineNr">564 </span>  <span class="Comment"># sandbox editor contains an illegal instruction</span>
 <span id="L565" class="LineNr">565 </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">[get 1234:num, foo:offset]</span>
 <span id="L566" class="LineNr">566 </span>  assume-console [
-<span id="L567" class="LineNr">567 </span>    press F4
+<span id="L567" class="LineNr">567 </span>  <span class="Conceal">¦</span> press F4
 <span id="L568" class="LineNr">568 </span>  ]
 <span id="L569" class="LineNr">569 </span>  run [
-<span id="L570" class="LineNr">570 </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="L570" class="LineNr">570 </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="L571" class="LineNr">571 </span>  ]
 <span id="L572" class="LineNr">572 </span>  <span class="Comment"># check that screen prints error message in red</span>
 <span id="L573" class="LineNr">573 </span>  screen-should-contain [
-<span id="L574" class="LineNr">574 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
-<span id="L575" class="LineNr">575 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L576" class="LineNr">576 </span><span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L577" class="LineNr">577 </span>   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L578" class="LineNr">578 </span>   <span class="Constant"> .                                                  ╎get 1234:num, foo:offset                         .</span>
-<span id="L579" class="LineNr">579 </span>   <span class="Constant"> .                                                  ╎unknown element 'foo' in container 'number'      .</span>
-<span id="L580" class="LineNr">580 </span>   <span class="Constant"> .                                                  ╎first ingredient of 'get' should be a container,↩.</span>
-<span id="L581" class="LineNr">581 </span>   <span class="Constant"> .                                                  ╎ but got '1234:num'                              .</span>
-<span id="L582" class="LineNr">582 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L583" class="LineNr">583 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L574" class="LineNr">574 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L575" class="LineNr">575 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L576" class="LineNr">576 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L577" class="LineNr">577 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L578" class="LineNr">578 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎get 1234:num, foo:offset                         .</span>
+<span id="L579" class="LineNr">579 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎unknown element 'foo' in container 'number'      .</span>
+<span id="L580" class="LineNr">580 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎first ingredient of 'get' should be a container,↩.</span>
+<span id="L581" class="LineNr">581 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎ but got '1234:num'                              .</span>
+<span id="L582" class="LineNr">582 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L583" class="LineNr">583 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L584" class="LineNr">584 </span>  ]
 <span id="L585" class="LineNr">585 </span>  screen-should-contain-in-color <span class="Constant">7/white</span>, [
-<span id="L586" class="LineNr">586 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L587" class="LineNr">587 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L588" class="LineNr">588 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L589" class="LineNr">589 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L590" class="LineNr">590 </span>   <span class="Constant"> .                                                   get 1234:num, foo:offset                         .</span>
-<span id="L591" class="LineNr">591 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L592" class="LineNr">592 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L593" class="LineNr">593 </span>   <span class="Constant"> .                                                                                                    .</span>
+<span id="L586" class="LineNr">586 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L587" class="LineNr">587 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L588" class="LineNr">588 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L589" class="LineNr">589 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L590" class="LineNr">590 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                   get 1234:num, foo:offset                         .</span>
+<span id="L591" class="LineNr">591 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L592" class="LineNr">592 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L593" class="LineNr">593 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
 <span id="L594" class="LineNr">594 </span>  ]
 <span id="L595" class="LineNr">595 </span>  screen-should-contain-in-color <span class="Constant">1/red</span>, [
-<span id="L596" class="LineNr">596 </span>   <span class="Constant"> .  errors found (0)                                                                                  .</span>
-<span id="L597" class="LineNr">597 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L598" class="LineNr">598 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L599" class="LineNr">599 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L600" class="LineNr">600 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L601" class="LineNr">601 </span>   <span class="Constant"> .                                                   unknown element 'foo' in container 'number'      .</span>
-<span id="L602" class="LineNr">602 </span>   <span class="Constant"> .                                                   first ingredient of 'get' should be a container, .</span>
-<span id="L603" class="LineNr">603 </span>   <span class="Constant"> .                                                    but got '1234:num'                              .</span>
-<span id="L604" class="LineNr">604 </span>   <span class="Constant"> .                                                                                                    .</span>
+<span id="L596" class="LineNr">596 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                                                  .</span>
+<span id="L597" class="LineNr">597 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L598" class="LineNr">598 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L599" class="LineNr">599 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L600" class="LineNr">600 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L601" class="LineNr">601 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                   unknown element 'foo' in container 'number'      .</span>
+<span id="L602" class="LineNr">602 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                   first ingredient of 'get' should be a container, .</span>
+<span id="L603" class="LineNr">603 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                    but got '1234:num'                              .</span>
+<span id="L604" class="LineNr">604 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
 <span id="L605" class="LineNr">605 </span>  ]
 <span id="L606" class="LineNr">606 </span>  screen-should-contain-in-color <span class="Constant">245/grey</span>, [
-<span id="L607" class="LineNr">607 </span>   <span class="Constant"> .                                                                                                    .</span>
-<span id="L608" class="LineNr">608 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L609" class="LineNr">609 </span><span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L610" class="LineNr">610 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L611" class="LineNr">611 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L612" class="LineNr">612 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L613" class="LineNr">613 </span>   <span class="Constant"> .                                                  ╎                                                ↩.</span>
-<span id="L614" class="LineNr">614 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L615" class="LineNr">615 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L616" class="LineNr">616 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L607" class="LineNr">607 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                                    .</span>
+<span id="L608" class="LineNr">608 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L609" class="LineNr">609 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L610" class="LineNr">610 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L611" class="LineNr">611 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L612" class="LineNr">612 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L613" class="LineNr">613 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                ↩.</span>
+<span id="L614" class="LineNr">614 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L615" class="LineNr">615 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L616" class="LineNr">616 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L617" class="LineNr">617 </span>  ]
 <span id="L618" class="LineNr">618 </span>]
 <span id="L619" class="LineNr">619 </span>
@@ -688,24 +689,24 @@ if ('onhashchange' in window) {
 <span id="L627" class="LineNr">627 </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">[get 1234:num, foo:offset]</span>
 <span id="L628" class="LineNr">628 </span>  <span class="Comment"># run the code in the editors multiple times</span>
 <span id="L629" class="LineNr">629 </span>  assume-console [
-<span id="L630" class="LineNr">630 </span>    press F4
-<span id="L631" class="LineNr">631 </span>    press F4
+<span id="L630" class="LineNr">630 </span>  <span class="Conceal">¦</span> press F4
+<span id="L631" class="LineNr">631 </span>  <span class="Conceal">¦</span> press F4
 <span id="L632" class="LineNr">632 </span>  ]
 <span id="L633" class="LineNr">633 </span>  run [
-<span id="L634" class="LineNr">634 </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="L634" class="LineNr">634 </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="L635" class="LineNr">635 </span>  ]
 <span id="L636" class="LineNr">636 </span>  <span class="Comment"># check that screen prints error message just once</span>
 <span id="L637" class="LineNr">637 </span>  screen-should-contain [
-<span id="L638" class="LineNr">638 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
-<span id="L639" class="LineNr">639 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L640" class="LineNr">640 </span><span class="Constant">    .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L641" class="LineNr">641 </span>   <span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L642" class="LineNr">642 </span>   <span class="Constant"> .                                                  ╎get 1234:num, foo:offset                         .</span>
-<span id="L643" class="LineNr">643 </span>   <span class="Constant"> .                                                  ╎unknown element 'foo' in container 'number'      .</span>
-<span id="L644" class="LineNr">644 </span>   <span class="Constant"> .                                                  ╎first ingredient of 'get' should be a container,↩.</span>
-<span id="L645" class="LineNr">645 </span>   <span class="Constant"> .                                                  ╎ but got '1234:num'                              .</span>
-<span id="L646" class="LineNr">646 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L647" class="LineNr">647 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L638" class="LineNr">638 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L639" class="LineNr">639 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L640" class="LineNr">640 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L641" class="LineNr">641 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L642" class="LineNr">642 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎get 1234:num, foo:offset                         .</span>
+<span id="L643" class="LineNr">643 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎unknown element 'foo' in container 'number'      .</span>
+<span id="L644" class="LineNr">644 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎first ingredient of 'get' should be a container,↩.</span>
+<span id="L645" class="LineNr">645 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎ but got '1234:num'                              .</span>
+<span id="L646" class="LineNr">646 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L647" class="LineNr">647 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L648" class="LineNr">648 </span>  ]
 <span id="L649" class="LineNr">649 </span>]
 <span id="L650" class="LineNr">650 </span>
@@ -715,32 +716,32 @@ if ('onhashchange' in window) {
 <span id="L654" class="LineNr">654 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
 <span id="L655" class="LineNr">655 </span>  <span class="Comment"># sandbox editor will trigger an infinite loop</span>
 <span id="L656" class="LineNr">656 </span>  assume-resources [
-<span id="L657" class="LineNr">657 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L658" class="LineNr">658 </span>      <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L659" class="LineNr">659 </span><span class="Constant">      |  {|</span>
-<span id="L660" class="LineNr">660 </span><span class="Constant">      |    loop|</span>
-<span id="L661" class="LineNr">661 </span><span class="Constant">      |  }|</span>
-<span id="L662" class="LineNr">662 </span><span class="Constant">      |]</span>|
-<span id="L663" class="LineNr">663 </span>    ]
+<span id="L657" class="LineNr">657 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L658" class="LineNr">658 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L659" class="LineNr">659 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  {|</span>
+<span id="L660" class="LineNr">660 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |    loop|</span>
+<span id="L661" class="LineNr">661 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  }|</span>
+<span id="L662" class="LineNr">662 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
+<span id="L663" class="LineNr">663 </span>  <span class="Conceal">¦</span> ]
 <span id="L664" class="LineNr">664 </span>  ]
 <span id="L665" class="LineNr">665 </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">[foo]</span>
 <span id="L666" class="LineNr">666 </span>  <span class="Comment"># run the sandbox</span>
 <span id="L667" class="LineNr">667 </span>  assume-console [
-<span id="L668" class="LineNr">668 </span>    press F4
+<span id="L668" class="LineNr">668 </span>  <span class="Conceal">¦</span> press F4
 <span id="L669" class="LineNr">669 </span>  ]
 <span id="L670" class="LineNr">670 </span>  run [
-<span id="L671" class="LineNr">671 </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="L671" class="LineNr">671 </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="L672" class="LineNr">672 </span>  ]
 <span id="L673" class="LineNr">673 </span>  screen-should-contain [
-<span id="L674" class="LineNr">674 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
-<span id="L675" class="LineNr">675 </span>   <span class="Constant"> .recipe foo [                                      ╎                                                 .</span>
-<span id="L676" class="LineNr">676 </span>   <span class="Constant"> .  {                                               ╎─────────────────────────────────────────────────.</span>
-<span id="L677" class="LineNr">677 </span>   <span class="Constant"> .    loop                                          ╎0   edit          copy            delete         .</span>
-<span id="L678" class="LineNr">678 </span>   <span class="Constant"> .  }                                               ╎foo                                              .</span>
-<span id="L679" class="LineNr">679 </span>   <span class="Constant"> .]                                                 ╎took too long!                                   .</span>
-<span id="L680" class="LineNr">680 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L681" class="LineNr">681 </span>   <span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L682" class="LineNr">682 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L674" class="LineNr">674 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L675" class="LineNr">675 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎                                                 .</span>
+<span id="L676" class="LineNr">676 </span>  <span class="Conceal">¦</span><span class="Constant"> .  {                                               ╎─────────────────────────────────────────────────.</span>
+<span id="L677" class="LineNr">677 </span>  <span class="Conceal">¦</span><span class="Constant"> .    loop                                          ╎0   edit          copy            delete         .</span>
+<span id="L678" class="LineNr">678 </span>  <span class="Conceal">¦</span><span class="Constant"> .  }                                               ╎foo                                              .</span>
+<span id="L679" class="LineNr">679 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎took too long!                                   .</span>
+<span id="L680" class="LineNr">680 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L681" class="LineNr">681 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L682" class="LineNr">682 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L683" class="LineNr">683 </span>  ]
 <span id="L684" class="LineNr">684 </span>]
 <span id="L685" class="LineNr">685 </span>
@@ -750,55 +751,55 @@ if ('onhashchange' in window) {
 <span id="L689" class="LineNr">689 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
 <span id="L690" class="LineNr">690 </span>  <span class="Comment"># generate a stash and a error</span>
 <span id="L691" class="LineNr">691 </span>  assume-resources [
-<span id="L692" class="LineNr">692 </span>    <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L693" class="LineNr">693 </span>      <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L694" class="LineNr">694 </span><span class="Constant">      |  local-scope|</span>
-<span id="L695" class="LineNr">695 </span><span class="Constant">      |  a:num &lt;- next-ingredient|</span>
-<span id="L696" class="LineNr">696 </span><span class="Constant">      |  b:num &lt;- next-ingredient|</span>
-<span id="L697" class="LineNr">697 </span><span class="Constant">      |  stash [dividing by]</span>, b|
-<span id="L698" class="LineNr">698 </span>      <span class="Constant">|</span>  _, c:num <span class="Special">&lt;-</span> divide-with-remainder a, b|
-<span id="L699" class="LineNr">699 </span>      <span class="Constant">|</span>  <span class="muControl">reply</span> b|
-<span id="L700" class="LineNr">700 </span><span class="Constant">      |]|</span>
-<span id="L701" class="LineNr">701 </span>    ]
+<span id="L692" class="LineNr">692 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L693" class="LineNr">693 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L694" class="LineNr">694 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  local-scope|</span>
+<span id="L695" class="LineNr">695 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  a:num &lt;- next-ingredient|</span>
+<span id="L696" class="LineNr">696 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  b:num &lt;- next-ingredient|</span>
+<span id="L697" class="LineNr">697 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  stash [dividing by]</span>, b|
+<span id="L698" class="LineNr">698 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|</span>  _, c:num <span class="Special">&lt;-</span> divide-with-remainder a, b|
+<span id="L699" class="LineNr">699 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|</span>  <span class="muControl">reply</span> b|
+<span id="L700" class="LineNr">700 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]|</span>
+<span id="L701" class="LineNr">701 </span>  <span class="Conceal">¦</span> ]
 <span id="L702" class="LineNr">702 </span>  ]
 <span id="L703" class="LineNr">703 </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">[foo 4, 0]</span>
 <span id="L704" class="LineNr">704 </span>  <span class="Comment"># run</span>
 <span id="L705" class="LineNr">705 </span>  assume-console [
-<span id="L706" class="LineNr">706 </span>    press F4
+<span id="L706" class="LineNr">706 </span>  <span class="Conceal">¦</span> press F4
 <span id="L707" class="LineNr">707 </span>  ]
 <span id="L708" class="LineNr">708 </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="L709" class="LineNr">709 </span>  <span class="Comment"># screen prints error message</span>
 <span id="L710" class="LineNr">710 </span>  screen-should-contain [
-<span id="L711" class="LineNr">711 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
-<span id="L712" class="LineNr">712 </span>   <span class="Constant"> .recipe foo [                                      ╎                                                 .</span>
-<span id="L713" class="LineNr">713 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L714" class="LineNr">714 </span>   <span class="Constant"> .  a:num &lt;- next-ingredient                        ╎0   edit          copy            delete         .</span>
-<span id="L715" class="LineNr">715 </span>   <span class="Constant"> .  b:num &lt;- next-ingredient                        ╎foo 4, 0                                         .</span>
-<span id="L716" class="LineNr">716 </span>   <span class="Constant"> .  stash [dividing by], b                          ╎foo: divide by zero in '_, c:num &lt;- divide-with-↩.</span>
-<span id="L717" class="LineNr">717 </span>   <span class="Constant"> .  _, c:num &lt;- divide-with-remainder a, b          ╎remainder a, b'                                  .</span>
-<span id="L718" class="LineNr">718 </span>   <span class="Constant"> .  reply b                                         ╎─────────────────────────────────────────────────.</span>
-<span id="L719" class="LineNr">719 </span>   <span class="Constant"> .]                                                 ╎                                                 .</span>
-<span id="L720" class="LineNr">720 </span>   <span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L711" class="LineNr">711 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L712" class="LineNr">712 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎                                                 .</span>
+<span id="L713" class="LineNr">713 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L714" class="LineNr">714 </span>  <span class="Conceal">¦</span><span class="Constant"> .  a:num &lt;- next-ingredient                        ╎0   edit          copy            delete         .</span>
+<span id="L715" class="LineNr">715 </span>  <span class="Conceal">¦</span><span class="Constant"> .  b:num &lt;- next-ingredient                        ╎foo 4, 0                                         .</span>
+<span id="L716" class="LineNr">716 </span>  <span class="Conceal">¦</span><span class="Constant"> .  stash [dividing by], b                          ╎foo: divide by zero in '_, c:num &lt;- divide-with-↩.</span>
+<span id="L717" class="LineNr">717 </span>  <span class="Conceal">¦</span><span class="Constant"> .  _, c:num &lt;- divide-with-remainder a, b          ╎remainder a, b'                                  .</span>
+<span id="L718" class="LineNr">718 </span>  <span class="Conceal">¦</span><span class="Constant"> .  reply b                                         ╎─────────────────────────────────────────────────.</span>
+<span id="L719" class="LineNr">719 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎                                                 .</span>
+<span id="L720" class="LineNr">720 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
 <span id="L721" class="LineNr">721 </span>  ]
 <span id="L722" class="LineNr">722 </span>  <span class="Comment"># click on the call in the sandbox</span>
 <span id="L723" class="LineNr">723 </span>  assume-console [
-<span id="L724" class="LineNr">724 </span>    left-click<span class="Constant"> 4</span>,<span class="Constant"> 55</span>
+<span id="L724" class="LineNr">724 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 4</span>,<span class="Constant"> 55</span>
 <span id="L725" class="LineNr">725 </span>  ]
 <span id="L726" class="LineNr">726 </span>  run [
-<span id="L727" class="LineNr">727 </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="L727" class="LineNr">727 </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="L728" class="LineNr">728 </span>  ]
 <span id="L729" class="LineNr">729 </span>  <span class="Comment"># screen should expand trace</span>
 <span id="L730" class="LineNr">730 </span>  screen-should-contain [
-<span id="L731" class="LineNr">731 </span>   <span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
-<span id="L732" class="LineNr">732 </span>   <span class="Constant"> .recipe foo [                                      ╎                                                 .</span>
-<span id="L733" class="LineNr">733 </span>   <span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
-<span id="L734" class="LineNr">734 </span>   <span class="Constant"> .  a:num &lt;- next-ingredient                        ╎0   edit          copy            delete         .</span>
-<span id="L735" class="LineNr">735 </span>   <span class="Constant"> .  b:num &lt;- next-ingredient                        ╎foo 4, 0                                         .</span>
-<span id="L736" class="LineNr">736 </span>   <span class="Constant"> .  stash [dividing by], b                          ╎dividing by 0                                    .</span>
-<span id="L737" class="LineNr">737 </span>   <span class="Constant"> .  _, c:num &lt;- divide-with-remainder a, b          ╎14 instructions run                              .</span>
-<span id="L738" class="LineNr">738 </span>   <span class="Constant"> .  reply b                                         ╎foo: divide by zero in '_, c:num &lt;- divide-with-↩.</span>
-<span id="L739" class="LineNr">739 </span>   <span class="Constant"> .]                                                 ╎remainder a, b'                                  .</span>
-<span id="L740" class="LineNr">740 </span>   <span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L731" class="LineNr">731 </span>  <span class="Conceal">¦</span><span class="Constant"> .  errors found (0)                                                               run (F4)           .</span>
+<span id="L732" class="LineNr">732 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎                                                 .</span>
+<span id="L733" class="LineNr">733 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎─────────────────────────────────────────────────.</span>
+<span id="L734" class="LineNr">734 </span>  <span class="Conceal">¦</span><span class="Constant"> .  a:num &lt;- next-ingredient                        ╎0   edit          copy            delete         .</span>
+<span id="L735" class="LineNr">735 </span>  <span class="Conceal">¦</span><span class="Constant"> .  b:num &lt;- next-ingredient                        ╎foo 4, 0                                         .</span>
+<span id="L736" class="LineNr">736 </span>  <span class="Conceal">¦</span><span class="Constant"> .  stash [dividing by], b                          ╎dividing by 0                                    .</span>
+<span id="L737" class="LineNr">737 </span>  <span class="Conceal">¦</span><span class="Constant"> .  _, c:num &lt;- divide-with-remainder a, b          ╎14 instructions run                              .</span>
+<span id="L738" class="LineNr">738 </span>  <span class="Conceal">¦</span><span class="Constant"> .  reply b                                         ╎foo: divide by zero in '_, c:num &lt;- divide-with-↩.</span>
+<span id="L739" class="LineNr">739 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎remainder a, b'                                  .</span>
+<span id="L740" class="LineNr">740 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
 <span id="L741" class="LineNr">741 </span>  ]
 <span id="L742" class="LineNr">742 </span>]
 </pre>