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-rw-r--r--html/edit.mu.html1510
1 files changed, 982 insertions, 528 deletions
diff --git a/html/edit.mu.html b/html/edit.mu.html
index 8481c441..3eb34a4b 100644
--- a/html/edit.mu.html
+++ b/html/edit.mu.html
@@ -33,43 +33,71 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 </head>
 <body>
 <pre id='vimCodeElement'>
-<span class="Comment"># Editor widget: takes a string and screen coordinates, modifying them in place.</span>
+<span class="Comment"># Environment for learning programming using mu.</span>
 
 <span class="muRecipe">recipe</span> main [
   <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
   open-console
-  width:number<span class="Special"> &lt;- </span>display-width
-  height:number<span class="Special"> &lt;- </span>display-height
-  <span class="Comment"># draw a line</span>
+  initial-recipe:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[recipe new-add [</span>
+<span class="Constant">  x:number &lt;- next-ingredient</span>
+<span class="Constant">  y:number &lt;- next-ingredient</span>
+<span class="Constant">  z:number &lt;- add x:number, y:number</span>
+<span class="Constant">  reply z:number</span>
+<span class="Constant">]</span>]
+  initial-sandbox:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[new-add 2:literal, 3:literal]</span>
+  env:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment <span class="Constant">0:literal/screen</span>, initial-recipe:address:array:character, initial-sandbox:address:array:character
+  render-all <span class="Constant">0:literal/address</span>, env:address:programming-environment-data
+  event-loop <span class="Constant">0:literal/screen</span>, <span class="Constant">0:literal/console</span>, env:address:programming-environment-data
+]
+
+container programming-environment-data [
+  recipes:address:editor-data
+  recipe-warnings:address:array:character
+  current-sandbox:address:editor-data
+  sandbox:address:sandbox-data
+  sandbox-in-focus?:boolean  <span class="Comment"># false =&gt; focus in recipes; true =&gt; focus in current-sandbox</span>
+]
+
+<span class="muRecipe">recipe</span> new-programming-environment [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  initial-recipe-contents:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  initial-sandbox-contents:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  width:number<span class="Special"> &lt;- </span>screen-width screen:address
+  height:number<span class="Special"> &lt;- </span>screen-height screen:address
+  <span class="Comment"># top menu</span>
+  result:address:programming-environment-data<span class="Special"> &lt;- </span>new programming-environment-data:type
+  draw-horizontal screen:address, <span class="Constant">0:literal</span>, <span class="Constant">0:literal/left</span>, width:number, <span class="Constant">32:literal/space</span>, <span class="Constant">0:literal/black</span>, <span class="Constant">238:literal/grey</span>
+  button-start:number<span class="Special"> &lt;- </span>subtract width:number, <span class="Constant">20:literal</span>
+  button-on-screen?:boolean<span class="Special"> &lt;- </span>greater-or-equal button-start:number, <span class="Constant">0:literal</span>
+  assert button-on-screen?:boolean, <span class="Constant">[screen too narrow for menu]</span>
+  move-cursor screen:address, <span class="Constant">0:literal/row</span>, button-start:number/column
+  run-button:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ run (F10)  ]</span>
+  print-string screen:address, run-button:address:array:character, <span class="Constant">255:literal/white</span>, <span class="Constant">161:literal/reddish</span>
+  <span class="Comment"># dotted line down the middle</span>
   divider:number, _<span class="Special"> &lt;- </span>divide-with-remainder width:number, <span class="Constant">2:literal</span>
-  draw-vertical <span class="Constant">0:literal/screen</span>, divider:number, <span class="Constant">0:literal/top</span>, height:number
-  <span class="Comment"># editor on the left</span>
-  left:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  left-editor:address:editor-data<span class="Special"> &lt;- </span>new-editor left:address:array:character, <span class="Constant">0:literal/screen</span>, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span> <span class="Comment">#divider:number/right</span>
-  <span class="Comment"># editor on the right</span>
-  right:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-  new-left:number<span class="Special"> &lt;- </span>add divider:number/right, <span class="Constant">1:literal</span>
-  right-editor:address:editor-data<span class="Special"> &lt;- </span>new-editor right:address:array:character, <span class="Constant">0:literal/screen</span>, <span class="Constant">0:literal/top</span>, new-left:number, width:number
-  <span class="Comment"># chain</span>
-  x:address:address:editor-data<span class="Special"> &lt;- </span>get-address left-editor:address:editor-data/deref, next-editor:offset
-  x:address:address:editor-data/deref<span class="Special"> &lt;- </span>copy right-editor:address:editor-data
-  <span class="Comment"># initialize focus</span>
-  reset-focus left-editor:address:editor-data
-  cursor-row:number<span class="Special"> &lt;- </span>get left-editor:address:editor-data/deref, cursor-row:offset
-  cursor-column:number<span class="Special"> &lt;- </span>get left-editor:address:editor-data/deref, cursor-column:offset
-  move-cursor <span class="Constant">0:literal/screen</span>, cursor-row:number, cursor-column:number
-  <span class="Comment"># and we're off!</span>
-  event-loop <span class="Constant">0:literal/screen</span>, <span class="Constant">0:literal/events</span>, left-editor:address:editor-data
-  close-console
+  draw-vertical screen:address, divider:number, <span class="Constant">1:literal/top</span>, height:number, <span class="Constant">9482:literal/vertical-dotted</span>
+  <span class="Comment"># recipe editor on the left</span>
+  recipes:address:address:editor-data<span class="Special"> &lt;- </span>get-address result:address:programming-environment-data/deref, recipes:offset
+  recipes:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor initial-recipe-contents:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, divider:number/right
+  <span class="Comment"># sandbox editor on the right</span>
+  new-left:number<span class="Special"> &lt;- </span>add divider:number, <span class="Constant">1:literal</span>
+  new-right:number<span class="Special"> &lt;- </span>add new-left:number, <span class="Constant">5:literal</span>
+  current-sandbox:address:address:editor-data<span class="Special"> &lt;- </span>get-address result:address:programming-environment-data/deref, current-sandbox:offset
+  current-sandbox:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor initial-sandbox-contents:address:array:character, screen:address, new-left:number, width:number
+  <span class="Comment"># initialize cursor</span>
+  update-cursor screen:address, recipes:address:address:editor-data/deref, current-sandbox:address:address:editor-data/deref, <span class="Constant">0:literal/focus-in-recipes</span>
+  <span class="muControl">reply</span> result:address:programming-environment-data
 ]
 
 <span class="muScenario">scenario</span> editor-initially-prints-string-to-screen [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   run [
     1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+    new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .          .</span>
   ]
@@ -79,30 +107,21 @@ body { font-family: monospace; color: #eeeeee; background-color: #080808; }
 <span class="SalientComment">## text to the screen.</span>
 
 container editor-data [
-  <span class="Comment"># doubly linked list of characters (head contains a special sentinel)</span>
+  <span class="Comment"># editable text: doubly linked list of characters (head contains a special sentinel)</span>
   data:address:duplex-list
-  <span class="Comment"># location of top-left of screen inside data (scrolling)</span>
-  top-of-screen:address:duplex-list
   <span class="Comment"># location before cursor inside data</span>
   before-cursor:address:duplex-list
 
-  screen:address:screen
   <span class="Comment"># raw bounds of display area on screen</span>
-  top:number
+  <span class="Comment"># always displays from row 1 and at most until bottom of screen</span>
   left:number
-  bottom:number
   right:number
   <span class="Comment"># raw screen coordinates of cursor</span>
   cursor-row:number
   cursor-column:number
-
-  <span class="Comment"># pointer to another editor, responsible for a different area of screen.</span>
-  <span class="Comment"># helps organize editors in a 'chain'.</span>
-  next-editor:address:editor-data
-  in-focus?:boolean  <span class="Comment"># set for the one editor in this chain currently being edited</span>
 ]
 
-<span class="Comment"># editor:address, screen:address &lt;- new-editor s:address:array:character, screen:address, top:number, left:number, bottom:number</span>
+<span class="Comment"># editor:address, screen:address &lt;- new-editor s:address:array:character, screen:address, left:number, right:number</span>
 <span class="Comment"># creates a new editor widget and renders its initial appearance to screen.</span>
 <span class="Comment">#   top/left/right constrain the screen area available to the new editor.</span>
 <span class="Comment">#   right is exclusive.</span>
@@ -111,42 +130,24 @@ container editor-data [
   s:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   <span class="Comment"># no clipping of bounds</span>
-  top:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   right:number<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>
   result:address:editor-data<span class="Special"> &lt;- </span>new editor-data:type
   <span class="Comment"># initialize screen-related fields</span>
-  sc:address:address:screen<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, screen:offset
-  sc:address:address:screen/deref<span class="Special"> &lt;- </span>copy screen:address
-  x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, top:offset
-  x:address:number/deref<span class="Special"> &lt;- </span>copy top:number
   x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, left:offset
   x:address:number/deref<span class="Special"> &lt;- </span>copy left:number
   x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, right:offset
   x:address:number/deref<span class="Special"> &lt;- </span>copy right:number
-  <span class="Comment"># bottom = top (in case of early exit)</span>
-  x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, bottom:offset
-  x:address:number/deref<span class="Special"> &lt;- </span>copy top:number
   <span class="Comment"># initialize cursor</span>
   x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, cursor-row:offset
-  x:address:number/deref<span class="Special"> &lt;- </span>copy top:number
+  x:address:number/deref<span class="Special"> &lt;- </span>copy <span class="Constant">1:literal/top</span>
   x:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, cursor-column:offset
-<span class="CommentedCode">#?   $print left:number, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
   x:address:number/deref<span class="Special"> &lt;- </span>copy left:number
-  d:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, data:offset
-  d:address:address:duplex-list/deref<span class="Special"> &lt;- </span>push-duplex <span class="Constant">167:literal/§</span>, <span class="Constant">0:literal/tail</span>
+  init:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, data:offset
+  init:address:address:duplex-list/deref<span class="Special"> &lt;- </span>push-duplex <span class="Constant">167:literal/§</span>, <span class="Constant">0:literal/tail</span>
   y:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, before-cursor:offset
-  y:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy d:address:address:duplex-list/deref
-  init:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, top-of-screen:offset
-  init:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy d:address:address:duplex-list/deref
-  <span class="Comment"># set focus</span>
-  <span class="Comment"># if using multiple editors, must call reset-focus after chaining them all</span>
-  b:address:boolean<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, in-focus?:offset
-  b:address:boolean/deref<span class="Special"> &lt;- </span>copy <span class="Constant">1:literal/true</span>
-<span class="CommentedCode">#?   $print d:address:address:duplex-list/deref, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
+  y:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy init:address:address:duplex-list/deref
   <span class="Comment"># early exit if s is empty</span>
   <span class="muControl">reply-unless</span> s:address:array:character, result:address:editor-data
   len:number<span class="Special"> &lt;- </span>length s:address:array:character/deref
@@ -155,15 +156,9 @@ container editor-data [
   <span class="Comment"># now we can start appending the rest, character by character</span>
   curr:address:duplex-list<span class="Special"> &lt;- </span>copy init:address:address:duplex-list/deref
   <span class="Delimiter">{</span>
-<span class="CommentedCode">#?     $print idx:number, [ vs ], len:number, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-<span class="CommentedCode">#?     $print [append to ], curr:address:duplex-list, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
     done?:boolean<span class="Special"> &lt;- </span>greater-or-equal idx:number, len:number
     <span class="muControl">break-if</span> done?:boolean
     c:character<span class="Special"> &lt;- </span>index s:address:array:character/deref, idx:number
-<span class="CommentedCode">#?     $print [aa: ], c:character, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
     insert-duplex c:character, curr:address:duplex-list
     <span class="Comment"># next iter</span>
     curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
@@ -173,29 +168,24 @@ container editor-data [
   <span class="Comment"># initialize cursor to top of screen</span>
   y:address:address:duplex-list<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, before-cursor:offset
   y:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy init:address:address:duplex-list/deref
-  <span class="Comment"># perform initial rendering to screen</span>
-  bottom:address:number<span class="Special"> &lt;- </span>get-address result:address:editor-data/deref, bottom:offset
-  result:address:editor-data<span class="Special"> &lt;- </span>render result:address:editor-data
+  <span class="Comment"># initial render to screen, just for some old tests</span>
+  _, screen:address<span class="Special"> &lt;- </span>render screen:address, result:address:editor-data
   <span class="muControl">reply</span> result:address:editor-data
 ]
 
 <span class="muScenario">scenario</span> editor-initializes-without-data [
   assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
   run [
-    1:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">0:literal/data</span>, screen:address, <span class="Constant">1:literal/top</span>, <span class="Constant">2:literal/left</span>, <span class="Constant">5:literal/right</span>
+    1:address:editor-data<span class="Special"> &lt;- </span>new-editor <span class="Constant">0:literal/data</span>, screen:address, <span class="Constant">2:literal/left</span>, <span class="Constant">5:literal/right</span>
     2:editor-data<span class="Special"> &lt;- </span>copy 1:address:editor-data/deref
   ]
   memory-should-contain [
-    <span class="Comment"># 2 &lt;- just the § sentinel</span>
-    <span class="Comment"># 3 (top of screen) &lt;- the § sentinel</span>
-    <span class="Comment"># 4 (before cursor) &lt;- the § sentinel</span>
-    <span class="Comment"># 5 &lt;- screen</span>
-    6<span class="Special"> &lt;- </span>1  <span class="Comment"># top</span>
-    7<span class="Special"> &lt;- </span>2  <span class="Comment"># left</span>
-    8<span class="Special"> &lt;- </span>1  <span class="Comment"># bottom</span>
-    9<span class="Special"> &lt;- </span>4  <span class="Comment"># right  (inclusive)</span>
-    10<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
-    11<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor column</span>
+    <span class="Comment"># 2 (data) &lt;- just the § sentinel</span>
+    <span class="Comment"># 3 (before cursor) &lt;- the § sentinel</span>
+    4<span class="Special"> &lt;- </span>2  <span class="Comment"># left</span>
+    5<span class="Special"> &lt;- </span>4  <span class="Comment"># right  (inclusive)</span>
+    6<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
+    7<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor column</span>
   ]
   screen-should-contain [
    <span class="Constant"> .     .</span>
@@ -204,23 +194,22 @@ container editor-data [
   ]
 ]
 
+<span class="Comment"># bottom:number, screen:address &lt;- render screen:address, editor:address:editor-data</span>
 <span class="muRecipe">recipe</span> render [
   <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-<span class="CommentedCode">#?   $print [=== render</span>
-<span class="CommentedCode">#? ] #? 2</span>
-  screen:address<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, screen:offset
-  top:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, top:offset
+  <span class="muControl">reply-unless</span> editor:address:editor-data, <span class="Constant">1:literal/top</span>, screen:address/same-as-ingredient:0
   left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
   screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
   right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
   hide-screen screen:address
   <span class="Comment"># traversing editor</span>
-  curr:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, top-of-screen:offset
+  curr:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
   prev:address:duplex-list<span class="Special"> &lt;- </span>copy curr:address:duplex-list
   curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
   <span class="Comment"># traversing screen</span>
-  row:number<span class="Special"> &lt;- </span>copy top:number
+  row:number<span class="Special"> &lt;- </span>copy <span class="Constant">1:literal/top</span>
   column:number<span class="Special"> &lt;- </span>copy left:number
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
@@ -228,8 +217,6 @@ container editor-data [
   move-cursor screen:address, row:number, column:number
   <span class="Delimiter">{</span>
 <span class="Constant">    +next-character</span>
-<span class="CommentedCode">#?     $print curr:address:duplex-list, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
     <span class="muControl">break-unless</span> curr:address:duplex-list
     off-screen?:boolean<span class="Special"> &lt;- </span>greater-or-equal row:number, screen-height:number
     <span class="muControl">break-if</span> off-screen?:boolean
@@ -242,13 +229,8 @@ container editor-data [
       at-cursor?:boolean<span class="Special"> &lt;- </span>equal column:number, cursor-column:address:number/deref
       <span class="muControl">break-unless</span> at-cursor?:boolean
       before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>prev-duplex curr:address:duplex-list
-<span class="CommentedCode">#?       new-prev:character &lt;- get before-cursor:address:address:duplex-list/deref/deref, value:offset #? 1</span>
-<span class="CommentedCode">#?       $print [render 0: cursor adjusted to after ], new-prev:character, [(], cursor-row:address:number/deref, [, ], cursor-column:address:number/deref, [)</span>
-<span class="CommentedCode">#? ] #? 1</span>
     <span class="Delimiter">}</span>
     c:character<span class="Special"> &lt;- </span>get curr:address:duplex-list/deref, value:offset
-<span class="CommentedCode">#?     $print [rendering ], c:character, [ </span>
-<span class="CommentedCode">#? ] #? 2</span>
     <span class="Delimiter">{</span>
       <span class="Comment"># newline? move to left rather than 0</span>
       newline?:boolean<span class="Special"> &lt;- </span>equal c:character, <span class="Constant">10:literal/newline</span>
@@ -261,22 +243,9 @@ container editor-data [
         <span class="muControl">break-unless</span> left-of-cursor?:boolean
         cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy column:number
         before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>prev-duplex curr:address:duplex-list
-<span class="CommentedCode">#?         new-prev:character &lt;- get before-cursor:address:address:duplex-list/deref/deref, value:offset #? 1</span>
-<span class="CommentedCode">#?         $print [render 1: cursor adjusted to after ], new-prev:character, [(], cursor-row:address:number/deref, [, ], cursor-column:address:number/deref, [)</span>
-<span class="CommentedCode">#? ] #? 1</span>
       <span class="Delimiter">}</span>
       <span class="Comment"># clear rest of line in this window</span>
-<span class="CommentedCode">#?       $print row:number, [ ], column:number, [ ], right:number, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-      <span class="Delimiter">{</span>
-        done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
-        <span class="muControl">break-if</span> done?:boolean
-        print-character screen:address, <span class="Constant">32:literal/space</span>
-        column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
-<span class="CommentedCode">#?         $print column:number, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-        <span class="muControl">loop</span>
-      <span class="Delimiter">}</span>
+      clear-line-delimited screen:address, column:number, right:number
       <span class="Comment"># skip to next line</span>
       row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
       column:number<span class="Special"> &lt;- </span>copy left:number
@@ -286,15 +255,11 @@ container editor-data [
       <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>
     <span class="Delimiter">}</span>
     <span class="Delimiter">{</span>
-      <span class="Comment"># at right? more than one letter left in the line? wrap</span>
+      <span class="Comment"># at right? wrap. even if there's only one more letter left; we need</span>
+      <span class="Comment"># room for clicking on the cursor after it.</span>
       at-right?:boolean<span class="Special"> &lt;- </span>equal column:number, right:number
       <span class="muControl">break-unless</span> at-right?:boolean
-      next-node:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
-      <span class="muControl">break-unless</span> next-node:address:duplex-list
-      next:character<span class="Special"> &lt;- </span>get next-node:address:duplex-list/deref, value:offset
-      next-character-is-newline?:boolean<span class="Special"> &lt;- </span>equal next:character, <span class="Constant">10:literal/newline</span>
-      <span class="muControl">break-if</span> next-character-is-newline?:boolean
-      <span class="Comment"># wrap</span>
+      <span class="Comment"># print wrap icon</span>
       print-character screen:address, <span class="Constant">8617:literal/loop-back-to-left</span>, <span class="Constant">245:literal/grey</span>
       column:number<span class="Special"> &lt;- </span>copy left:number
       row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
@@ -308,9 +273,6 @@ container editor-data [
     column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
-  <span class="Comment"># bottom = row</span>
-  bottom:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, bottom:offset
-  bottom:address:number/deref<span class="Special"> &lt;- </span>copy row:number
   <span class="Comment"># is cursor to the right of the last line? move to end</span>
   <span class="Delimiter">{</span>
     at-cursor-row?:boolean<span class="Special"> &lt;- </span>equal row:number, cursor-row:address:number/deref
@@ -319,12 +281,8 @@ container editor-data [
     above-cursor-row?:boolean<span class="Special"> &lt;- </span>lesser-than row:number, cursor-row:address:number/deref
     before-cursor?:boolean<span class="Special"> &lt;- </span>or before-cursor-on-same-line?:boolean, above-cursor-row?:boolean
     <span class="muControl">break-unless</span> before-cursor?:boolean
-<span class="CommentedCode">#?     $print [pointed after all text</span>
-<span class="CommentedCode">#? ] #? 1</span>
     cursor-row:address:number/deref<span class="Special"> &lt;- </span>copy row:number
     cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy column:number
-<span class="CommentedCode">#?     $print [render: cursor moved to ], cursor-row:address:number/deref, [, ], cursor-column:address:number/deref, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
     <span class="Comment"># line not wrapped but cursor outside bounds? wrap cursor</span>
     <span class="Delimiter">{</span>
       too-far-right?:boolean<span class="Special"> &lt;- </span>greater-than cursor-column:address:number/deref, right:number
@@ -334,62 +292,106 @@ container editor-data [
       above-screen-bottom?:boolean<span class="Special"> &lt;- </span>lesser-than cursor-row:address:number/deref, screen-height:number
       assert above-screen-bottom?:boolean, <span class="Constant">[unimplemented: wrapping cursor past bottom of screen]</span>
     <span class="Delimiter">}</span>
-<span class="CommentedCode">#?     $print [now ], cursor-row:address:number/deref, [, ], cursor-column:address:number/deref, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
     before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>copy prev:address:duplex-list
-<span class="CommentedCode">#?     new-prev:character &lt;- get before-cursor:address:address:duplex-list/deref/deref, value:offset #? 1</span>
-<span class="CommentedCode">#?     $print [render Ω: cursor adjusted to after ], new-prev:character, [(], cursor-row:address:number/deref, [, ], cursor-column:address:number/deref, [)</span>
-<span class="CommentedCode">#? ] #? 1</span>
   <span class="Delimiter">}</span>
-<span class="CommentedCode">#?   $print [clearing ], row:number, [ ], column:number, [ ], right:number, [ </span>
-<span class="CommentedCode">#? ] #? 2</span>
+  <span class="Comment"># clear rest of current line</span>
+  clear-line-delimited screen:address, column:number, right:number
+  <span class="muControl">reply</span> row:number, screen:address/same-as-ingredient:0
+]
+
+<span class="Comment"># row:number, screen:address &lt;- render-string screen:address, s:address:array:character, left:number, right:number, color:number, row:number</span>
+<span class="Comment"># print a string 's' to 'editor' in 'color' starting at 'row'</span>
+<span class="Comment"># leave cursor at start of next line</span>
+<span class="muRecipe">recipe</span> render-string [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  s:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  color:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  row:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+  <span class="muControl">reply-unless</span> s:address:array:character, row:number/same-as-ingredient:5, screen:address/same-as-ingredient:0
+  column:number<span class="Special"> &lt;- </span>copy left:number
+  move-cursor screen:address, row:number, column:number
+  screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
+  len:number<span class="Special"> &lt;- </span>length s:address:array:character/deref
   <span class="Delimiter">{</span>
-    <span class="Comment"># clear rest of current line</span>
+<span class="Constant">    +next-character</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i:number, len:number
+    <span class="muControl">break-if</span> done?:boolean
     done?:boolean<span class="Special"> &lt;- </span>greater-or-equal row:number, screen-height:number
     <span class="muControl">break-if</span> done?:boolean
+    c:character<span class="Special"> &lt;- </span>index s:address:array:character/deref, i:number
     <span class="Delimiter">{</span>
-      line-done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
-      <span class="muControl">break-if</span> line-done?:boolean
-      print-character screen:address, <span class="Constant">32:literal/space</span>
-      column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
-      <span class="muControl">loop</span>
+      <span class="Comment"># at right? wrap.</span>
+      at-right?:boolean<span class="Special"> &lt;- </span>equal column:number, right:number
+      <span class="muControl">break-unless</span> at-right?:boolean
+      <span class="Comment"># print wrap icon</span>
+      print-character screen:address, <span class="Constant">8617:literal/loop-back-to-left</span>, <span class="Constant">245:literal/grey</span>
+      column:number<span class="Special"> &lt;- </span>copy left:number
+      row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+      move-cursor screen:address, row:number, column:number
+      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>  <span class="Comment"># retry i</span>
     <span class="Delimiter">}</span>
-    <span class="Comment"># clear one more line just in case we just backspaced out of it</span>
-    row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
-    column:number<span class="Special"> &lt;- </span>copy left:number
-    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal row:number, screen-height:number
-    <span class="muControl">break-if</span> done?:boolean
-    move-cursor screen:address, row:number, column:number
+    i:number<span class="Special"> &lt;- </span>add i:number, <span class="Constant">1:literal</span>
     <span class="Delimiter">{</span>
-      line-done?:boolean<span class="Special"> &lt;- </span>greater-or-equal column:number, right:number
-      <span class="muControl">break-if</span> line-done?:boolean
-      print-character screen:address, <span class="Constant">32:literal/space</span>
-      column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
-      <span class="muControl">loop</span>
+      <span class="Comment"># newline? move to left rather than 0</span>
+      newline?:boolean<span class="Special"> &lt;- </span>equal c:character, <span class="Constant">10:literal/newline</span>
+      <span class="muControl">break-unless</span> newline?:boolean
+      <span class="Comment"># clear rest of line in this window</span>
+      <span class="Delimiter">{</span>
+        done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
+        <span class="muControl">break-if</span> done?:boolean
+        print-character screen:address, <span class="Constant">32:literal/space</span>
+        column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
+        <span class="muControl">loop</span>
+      <span class="Delimiter">}</span>
+      row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+      column:number<span class="Special"> &lt;- </span>copy left:number
+      move-cursor screen:address, row:number, column:number
+      <span class="muControl">loop</span> <span class="Constant">+next-character:label</span>
     <span class="Delimiter">}</span>
+    print-character screen:address, c:character, color:number
+    column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
+    <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
-  <span class="Comment"># update cursor</span>
   <span class="Delimiter">{</span>
-    in-focus?:boolean<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, in-focus?:offset
-    <span class="muControl">break-unless</span> in-focus?:boolean
-    cursor-inside-right-margin?:boolean<span class="Special"> &lt;- </span>lesser-or-equal cursor-column:address:number/deref, right:number
-    assert cursor-inside-right-margin?:boolean, <span class="Constant">[cursor outside right margin]</span>
-    cursor-inside-left-margin?:boolean<span class="Special"> &lt;- </span>greater-or-equal cursor-column:address:number/deref, left:number
-    assert cursor-inside-left-margin?:boolean, <span class="Constant">[cursor outside left margin]</span>
-    move-cursor screen:address, cursor-row:address:number/deref, cursor-column:address:number/deref
+    <span class="Comment"># clear rest of current line</span>
+    line-done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
+    <span class="muControl">break-if</span> line-done?:boolean
+    print-character screen:address, <span class="Constant">32:literal/space</span>
+    column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+  <span class="muControl">reply</span> row:number/same-as-ingredient:5, screen:address/same-as-ingredient:0
+]
+
+<span class="muRecipe">recipe</span> clear-line-delimited [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  column:number<span class="Special"> &lt;- </span>copy left:number
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-than column:number, right:number
+    <span class="muControl">break-if</span> done?:boolean
+    print-character screen:address, <span class="Constant">32:literal/space</span>
+    column:number<span class="Special"> &lt;- </span>add column:number, <span class="Constant">1:literal</span>
+    <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
-  show-screen screen:address
-  <span class="muControl">reply</span> editor:address:editor-data/same-as-ingredient:0
 ]
 
 <span class="muScenario">scenario</span> editor-initially-prints-multiple-lines [
-  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
+  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
   run [
     s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   ]
   screen-should-contain [
+   <span class="Constant"> .     .</span>
    <span class="Constant"> .abc  .</span>
    <span class="Constant"> .def  .</span>
    <span class="Constant"> .     .</span>
@@ -397,26 +399,27 @@ container editor-data [
 ]
 
 <span class="muScenario">scenario</span> editor-initially-handles-offsets [
-  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
+  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
   run [
     s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">1:literal/left</span>, <span class="Constant">5:literal/right</span>
+    new-editor s:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">5:literal/right</span>
   ]
   screen-should-contain [
-   <span class="Constant"> . abc .</span>
    <span class="Constant"> .     .</span>
+   <span class="Constant"> . abc .</span>
    <span class="Constant"> .     .</span>
   ]
 ]
 
 <span class="muScenario">scenario</span> editor-initially-prints-multiple-lines-at-offset [
-  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
+  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
   run [
     s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">1:literal/left</span>, <span class="Constant">5:literal/right</span>
+    new-editor s:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">5:literal/right</span>
   ]
   screen-should-contain [
+   <span class="Constant"> .     .</span>
    <span class="Constant"> . abc .</span>
    <span class="Constant"> . def .</span>
    <span class="Constant"> .     .</span>
@@ -424,17 +427,41 @@ container editor-data [
 ]
 
 <span class="muScenario">scenario</span> editor-initially-wraps-long-lines [
-  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
+  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
   run [
     s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc def]</span>
-    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   ]
   screen-should-contain [
+   <span class="Constant"> .     .</span>
    <span class="Constant"> .abc ↩.</span>
    <span class="Constant"> .def  .</span>
    <span class="Constant"> .     .</span>
   ]
   screen-should-contain-in-color, <span class="Constant">245:literal/grey</span> [
+   <span class="Constant"> .     .</span>
+   <span class="Constant"> .    ↩.</span>
+   <span class="Constant"> .     .</span>
+   <span class="Constant"> .     .</span>
+  ]
+]
+
+<span class="muScenario">scenario</span> editor-initially-wraps-barely-long-lines [
+  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
+  run [
+    s:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
+    new-editor s:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  ]
+  <span class="Comment"># still wrap, even though the line would fit. We need room to click on the</span>
+  <span class="Comment"># end of the line</span>
+  screen-should-contain [
+   <span class="Constant"> .     .</span>
+<span class="Constant">    .abcd↩.</span>
+   <span class="Constant"> .e    .</span>
+   <span class="Constant"> .     .</span>
+  ]
+  screen-should-contain-in-color, <span class="Constant">245:literal/grey</span> [
+   <span class="Constant"> .     .</span>
    <span class="Constant"> .    ↩.</span>
    <span class="Constant"> .     .</span>
    <span class="Constant"> .     .</span>
@@ -442,10 +469,10 @@ container editor-data [
 ]
 
 <span class="muScenario">scenario</span> editor-initializes-empty-text [
-  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
+  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
   run [
     1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-    2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+    2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
@@ -455,86 +482,112 @@ container editor-data [
    <span class="Constant"> .     .</span>
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor row</span>
+    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
     4<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor column</span>
   ]
 ]
 
 <span class="SalientComment">## handling events from the keyboard, mouse, touch screen, ...</span>
 
-<span class="Comment"># Takes a chain of editors (chained using editor-data.next-editor), sends each</span>
-<span class="Comment"># event from the console to each editor.</span>
 <span class="muRecipe">recipe</span> event-loop [
   <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
   screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   console:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  env:address:programming-environment-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  recipes:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipes:offset
+  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, current-sandbox:offset
+  sandbox-in-focus?:address:boolean<span class="Special"> &lt;- </span>get-address env:address:programming-environment-data/deref, sandbox-in-focus?:offset
   <span class="Delimiter">{</span>
-    <span class="Comment"># send each event to each editor</span>
+    <span class="Comment"># looping over each (keyboard or touch) event as it occurs</span>
+<span class="Constant">    +next-event</span>
     e:event, console:address, found?:boolean, quit?:boolean<span class="Special"> &lt;- </span>read-event console:address
     <span class="muControl">loop-unless</span> found?:boolean
     <span class="muControl">break-if</span> quit?:boolean  <span class="Comment"># only in tests</span>
     trace <span class="Constant">[app]</span>, <span class="Constant">[next-event]</span>
-<span class="CommentedCode">#?     $print [--- new event</span>
-<span class="CommentedCode">#? ] #? 1</span>
-    curr:address:editor-data<span class="Special"> &lt;- </span>copy editor:address:editor-data
+    <span class="Comment"># check for global events that will trigger regardless of which editor has focus</span>
     <span class="Delimiter">{</span>
-      <span class="muControl">break-unless</span> curr:address:editor-data
-      handle-event screen:address, console:address, curr:address:editor-data, e:event
-      curr:address:editor-data<span class="Special"> &lt;- </span>get curr:address:editor-data/deref, next-editor:offset
-      <span class="muControl">loop</span>
+      k:address:number<span class="Special"> &lt;- </span>maybe-convert e:event, keycode:variant
+      <span class="muControl">break-unless</span> k:address:number
+      <span class="Comment"># F10? load all code and run all sandboxes.</span>
+      <span class="Delimiter">{</span>
+        do-run?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65526:literal/F10</span>
+        <span class="muControl">break-unless</span> do-run?:boolean
+        run-sandboxes env:address:programming-environment-data
+        <span class="muControl">jump</span> <span class="Constant">+continue:label</span>
+      <span class="Delimiter">}</span>
     <span class="Delimiter">}</span>
-    <span class="Comment"># after each non-trivial event, render all editors</span>
-    curr:address:editor-data<span class="Special"> &lt;- </span>copy editor:address:editor-data
+    <span class="Comment"># 'touch' event - send to both editors</span>
     <span class="Delimiter">{</span>
-      <span class="muControl">break-unless</span> curr:address:editor-data
-      render curr:address:editor-data
-      curr:address:editor-data<span class="Special"> &lt;- </span>get curr:address:editor-data/deref, next-editor:offset
-      <span class="muControl">loop</span>
+      t:address:touch-event<span class="Special"> &lt;- </span>maybe-convert e:event, touch:variant
+      <span class="muControl">break-unless</span> t:address:touch-event
+      _<span class="Special"> &lt;- </span>move-cursor-in-editor screen:address, recipes:address:editor-data, t:address:touch-event/deref
+      sandbox-in-focus?:address:boolean/deref<span class="Special"> &lt;- </span>move-cursor-in-editor screen:address, current-sandbox:address:editor-data, t:address:touch-event/deref
+      <span class="muControl">jump</span> <span class="Constant">+continue:label</span>
     <span class="Delimiter">}</span>
-    <span class="Comment"># ..and position the cursor</span>
-    curr:address:editor-data<span class="Special"> &lt;- </span>copy editor:address:editor-data
+    <span class="Comment"># if it's not global, send to appropriate editor</span>
     <span class="Delimiter">{</span>
-      <span class="muControl">break-unless</span> curr:address:editor-data
       <span class="Delimiter">{</span>
-        in-focus?:boolean<span class="Special"> &lt;- </span>get curr:address:editor-data/deref, in-focus?:offset
-        <span class="muControl">break-unless</span> in-focus?:boolean
-        cursor-row:number<span class="Special"> &lt;- </span>get curr:address:editor-data/deref, cursor-row:offset
-        cursor-column:number<span class="Special"> &lt;- </span>get curr:address:editor-data/deref, cursor-column:offset
-        move-cursor screen:address, cursor-row:number, cursor-column:number
+        <span class="muControl">break-if</span> sandbox-in-focus?:address:boolean/deref
+        handle-event screen:address, console:address, recipes:address:editor-data, e:event
       <span class="Delimiter">}</span>
-      curr:address:editor-data<span class="Special"> &lt;- </span>get curr:address:editor-data/deref, next-editor:offset
-      <span class="muControl">loop</span>
+      <span class="Delimiter">{</span>
+        <span class="muControl">break-unless</span> sandbox-in-focus?:address:boolean/deref
+        handle-event screen:address, console:address, current-sandbox:address:editor-data, e:event
+      <span class="Delimiter">}</span>
+    <span class="Delimiter">}</span>
+<span class="Constant">    +continue</span>
+    <span class="Comment"># if no more events currently left to process, render</span>
+    <span class="Comment"># todo: test this</span>
+    <span class="Delimiter">{</span>
+      more-events?:boolean<span class="Special"> &lt;- </span>has-more-events? console:address
+      <span class="muControl">break-if</span> more-events?:boolean
+      render-all screen:address, env:address:programming-environment-data
     <span class="Delimiter">}</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
 ]
 
+<span class="Comment"># helper for testing a single editor</span>
+<span class="muRecipe">recipe</span> editor-event-loop [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  console:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># looping over each (keyboard or touch) event as it occurs</span>
+<span class="Constant">    +next-event</span>
+    e:event, console:address, found?:boolean, quit?:boolean<span class="Special"> &lt;- </span>read-event console:address
+    <span class="muControl">loop-unless</span> found?:boolean
+    <span class="muControl">break-if</span> quit?:boolean  <span class="Comment"># only in tests</span>
+    trace <span class="Constant">[app]</span>, <span class="Constant">[next-event]</span>
+    <span class="Comment"># 'touch' event - send to both editors</span>
+    <span class="Delimiter">{</span>
+      t:address:touch-event<span class="Special"> &lt;- </span>maybe-convert e:event, touch:variant
+      <span class="muControl">break-unless</span> t:address:touch-event
+      move-cursor-in-editor screen:address, editor:address:editor-data, t:address:touch-event/deref
+      <span class="muControl">jump</span> <span class="Constant">+continue:label</span>
+    <span class="Delimiter">}</span>
+    <span class="Comment"># other events - send to appropriate editor</span>
+    handle-event screen:address, console:address, editor:address:editor-data, e:event
+<span class="Constant">    +continue</span>
+    row:number, screen:address<span class="Special"> &lt;- </span>render screen:address, editor:address:editor-data
+    <span class="Comment"># clear next line, in case we just processed a backspace</span>
+    left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
+    right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
+    row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+    move-cursor screen:address, row:number, left:number
+    clear-line-delimited screen:address, left:number, right:number
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
 <span class="muRecipe">recipe</span> handle-event [
   <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">50:literal</span>
   screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   console:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   e:event<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-  <span class="Comment"># 'touch' event</span>
-  <span class="Delimiter">{</span>
-    t:address:touch-event<span class="Special"> &lt;- </span>maybe-convert e:event, touch:variant
-    <span class="muControl">break-unless</span> t:address:touch-event
-    move-cursor-in-editor editor:address:editor-data, t:address:touch-event/deref
-    <span class="muControl">reply</span>
-  <span class="Delimiter">}</span>
-  <span class="Comment"># other events trigger only if this editor is in focus</span>
-<span class="CommentedCode">#?   $print [checking ], editor:address:editor-data, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-<span class="CommentedCode">#?   x:address:boolean &lt;- get-address editor:address:editor-data/deref, in-focus?:offset #? 1</span>
-<span class="CommentedCode">#?   $print [address of focus: ], x:address:boolean, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-  in-focus?:address:boolean<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, in-focus?:offset
-<span class="CommentedCode">#?   $print [ at ], in-focus?:address:boolean, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-  <span class="muControl">reply-unless</span> in-focus?:address:boolean/deref
-<span class="CommentedCode">#?   $print [in focus: ], editor:address:editor-data, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
+  <span class="muControl">reply-unless</span> editor:address:editor-data
   <span class="Comment"># typing a character</span>
   <span class="Delimiter">{</span>
     c:address:character<span class="Special"> &lt;- </span>maybe-convert e:event, text:variant
@@ -546,7 +599,7 @@ container editor-data [
       delete-before-cursor editor:address:editor-data
       <span class="muControl">reply</span>
     <span class="Delimiter">}</span>
-    insert-at-cursor editor:address:editor-data, c:address:character/deref
+    insert-at-cursor editor:address:editor-data, c:address:character/deref, screen:address
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># otherwise it's a special key to control the editor</span>
@@ -557,7 +610,8 @@ container editor-data [
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
   screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
-  top:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, top:offset
+  left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
+  right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
   <span class="Comment"># arrows; update cursor-row and cursor-column, leave before-cursor to 'render'.</span>
   <span class="Comment"># right arrow</span>
   <span class="Delimiter">{</span>
@@ -574,7 +628,7 @@ container editor-data [
       was-at-newline?:boolean<span class="Special"> &lt;- </span>equal old-cursor-character:character, <span class="Constant">10:literal/newline</span>
       <span class="muControl">break-unless</span> was-at-newline?:boolean
       cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
-      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
+      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy left:number
       <span class="Comment"># todo: what happens when cursor is too far down?</span>
       screen-height:number<span class="Special"> &lt;- </span>screen-height screen:address
       above-screen-bottom?:boolean<span class="Special"> &lt;- </span>lesser-than cursor-row:address:number/deref, screen-height:number
@@ -584,21 +638,17 @@ container editor-data [
     <span class="Comment"># if the line wraps, move cursor to start of next row</span>
     <span class="Delimiter">{</span>
       <span class="Comment"># if we're at the column just before the wrap indicator</span>
-      right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
       wrap-column:number<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>
       at-wrap?:boolean<span class="Special"> &lt;- </span>equal cursor-column:address:number/deref, wrap-column:number
       <span class="muControl">break-unless</span> at-wrap?:boolean
-      <span class="Comment"># and if character after next isn't newline</span>
-<span class="CommentedCode">#?       $print [aaa] #? 1</span>
+      <span class="Comment"># and if next character isn't newline</span>
       new-cursor:address:duplex-list<span class="Special"> &lt;- </span>next-duplex old-cursor:address:duplex-list
       <span class="muControl">break-unless</span> new-cursor:address:duplex-list
-      next:address:duplex-list<span class="Special"> &lt;- </span>next-duplex new-cursor:address:duplex-list
-      <span class="muControl">break-unless</span> next:address:duplex-list
-      next-character:character<span class="Special"> &lt;- </span>get next:address:duplex-list/deref, value:offset
+      next-character:character<span class="Special"> &lt;- </span>get new-cursor:address:duplex-list/deref, value:offset
       newline?:boolean<span class="Special"> &lt;- </span>equal next-character:character, <span class="Constant">10:literal/newline</span>
       <span class="muControl">break-if</span> newline?:boolean
       cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
-      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
+      cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy left:number
       <span class="Comment"># todo: what happens when cursor is too far down?</span>
       above-screen-bottom?:boolean<span class="Special"> &lt;- </span>lesser-than cursor-row:address:number/deref, screen-height:number
       assert above-screen-bottom?:boolean, <span class="Constant">[unimplemented: moving past bottom of screen]</span>
@@ -611,6 +661,7 @@ container editor-data [
   <span class="Delimiter">{</span>
     move-to-previous-character?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65515:literal/left-arrow</span>
     <span class="muControl">break-unless</span> move-to-previous-character?:boolean
+<span class="CommentedCode">#?     trace [app], [left arrow] #? 1</span>
     <span class="Comment"># if not at start of text (before-cursor at § sentinel)</span>
     prev:address:duplex-list<span class="Special"> &lt;- </span>prev-duplex before-cursor:address:address:duplex-list/deref
     <span class="muControl">break-unless</span> prev:address:duplex-list
@@ -618,6 +669,7 @@ container editor-data [
     <span class="Delimiter">{</span>
       at-left-margin?:boolean<span class="Special"> &lt;- </span>equal cursor-column:address:number/deref, <span class="Constant">0:literal</span>
       <span class="muControl">break-if</span> at-left-margin?:boolean
+<span class="CommentedCode">#?       trace [app], [decrementing] #? 1</span>
       cursor-column:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-column:address:number/deref, <span class="Constant">1:literal</span>
       <span class="muControl">reply</span>
     <span class="Delimiter">}</span>
@@ -628,6 +680,7 @@ container editor-data [
       prevc:character<span class="Special"> &lt;- </span>get before-cursor:address:address:duplex-list/deref/deref, value:offset
       previous-character-is-newline?:boolean<span class="Special"> &lt;- </span>equal prevc:character, <span class="Constant">10:literal/newline</span>
       <span class="muControl">break-unless</span> previous-character-is-newline?:boolean
+<span class="CommentedCode">#?       trace [app], [previous line] #? 1</span>
       <span class="Comment"># compute length of previous line</span>
       end-of-line:number<span class="Special"> &lt;- </span>previous-line-length before-cursor:address:address:duplex-list/deref, d:address:duplex-list
       cursor-row:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-row:address:number/deref, <span class="Constant">1:literal</span>
@@ -637,7 +690,6 @@ container editor-data [
     <span class="Comment"># if before-cursor is not at newline, we're just at a wrapped line</span>
     assert cursor-row:address:number/deref, <span class="Constant">[unimplemented: moving cursor above top of screen]</span>
     cursor-row:address:number/deref<span class="Special"> &lt;- </span>subtract cursor-row:address:number/deref, <span class="Constant">1:literal</span>
-    right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
     cursor-column:address:number/deref<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>  <span class="Comment"># leave room for wrap icon</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># down arrow</span>
@@ -657,7 +709,7 @@ container editor-data [
     move-to-previous-line?:boolean<span class="Special"> &lt;- </span>equal k:address:number/deref, <span class="Constant">65517:literal/up-arrow</span>
     <span class="muControl">break-unless</span> move-to-previous-line?:boolean
     <span class="Comment"># todo: support scrolling</span>
-    already-at-top?:boolean<span class="Special"> &lt;- </span>lesser-or-equal cursor-row:address:number/deref, top:number
+    already-at-top?:boolean<span class="Special"> &lt;- </span>lesser-or-equal cursor-row:address:number/deref, <span class="Constant">1:literal/top</span>
     <span class="muControl">break-if</span> already-at-top?:boolean
 <span class="CommentedCode">#?     $print [moving up</span>
 <span class="CommentedCode">#? ] #? 1</span>
@@ -666,58 +718,58 @@ container editor-data [
   <span class="Delimiter">}</span>
 ]
 
+<span class="Comment"># process click, return if it was on current editor</span>
+<span class="Comment"># todo: ignores menu bar (for now just displays shortcuts)</span>
 <span class="muRecipe">recipe</span> move-cursor-in-editor [
   <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   t:touch-event<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-  <span class="Comment"># always reset focus to start</span>
-  in-focus?:address:boolean<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, in-focus?:offset
-  in-focus?:address:boolean/deref<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal/true</span>
+  <span class="muControl">reply-unless</span> editor:address:editor-data, <span class="Constant">0:literal/false</span>
   click-column:number<span class="Special"> &lt;- </span>get t:touch-event, column:offset
   left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
   too-far-left?:boolean<span class="Special"> &lt;- </span>lesser-than click-column:number, left:number
-  <span class="muControl">reply-if</span> too-far-left?:boolean
+  <span class="muControl">reply-if</span> too-far-left?:boolean, <span class="Constant">0:literal/false</span>
   right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
   too-far-right?:boolean<span class="Special"> &lt;- </span>greater-than click-column:number, right:number
-  <span class="muControl">reply-if</span> too-far-right?:boolean
-<span class="CommentedCode">#?   $print [focus now at ], editor:address:editor-data, [ </span>
-<span class="CommentedCode">#? ] #? 2</span>
-  <span class="Comment"># click on this window; gain focus</span>
-  in-focus?:address:boolean/deref<span class="Special"> &lt;- </span>copy <span class="Constant">1:literal/true</span>
+  <span class="muControl">reply-if</span> too-far-right?:boolean, <span class="Constant">0:literal/false</span>
   <span class="Comment"># update cursor</span>
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
   cursor-row:address:number/deref<span class="Special"> &lt;- </span>get t:touch-event, row:offset
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
   cursor-column:address:number/deref<span class="Special"> &lt;- </span>get t:touch-event, column:offset
-<span class="CommentedCode">#?   $print [column is at: ], cursor-column:address:number, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
+  render screen:address, editor:address:editor-data
+  <span class="Comment"># gain focus</span>
+  <span class="muControl">reply</span> <span class="Constant">1:literal/true</span>
 ]
 
 <span class="muRecipe">recipe</span> insert-at-cursor [
   <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
   editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   c:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
 <span class="CommentedCode">#?   $print [insert ], c:character, [ </span>
 <span class="CommentedCode">#? ] #? 1</span>
   before-cursor:address:address:duplex-list<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, before-cursor:offset
   d:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
   insert-duplex c:character, before-cursor:address:address:duplex-list/deref
-  screen:address<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, screen:offset
+  before-cursor:address:address:duplex-list/deref<span class="Special"> &lt;- </span>next-duplex before-cursor:address:address:duplex-list/deref
   cursor-row:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-row:offset
   cursor-column:address:number<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, cursor-column:offset
+  left:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, left:offset
+  right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
   <span class="Comment"># update cursor: if newline, move cursor to start of next line</span>
   <span class="Comment"># todo: bottom of screen</span>
   <span class="Delimiter">{</span>
     newline?:boolean<span class="Special"> &lt;- </span>equal c:character, <span class="Constant">10:literal/newline</span>
     <span class="muControl">break-unless</span> newline?:boolean
     cursor-row:address:number/deref<span class="Special"> &lt;- </span>add cursor-row:address:number/deref, <span class="Constant">1:literal</span>
-    cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
+    cursor-column:address:number/deref<span class="Special"> &lt;- </span>copy left:number
     <span class="muControl">reply</span>
   <span class="Delimiter">}</span>
   <span class="Comment"># if the line wraps at the cursor, move cursor to start of next row</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># if we're at the column just before the wrap indicator</span>
-    right:number<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, right:offset
     wrap-column:number<span class="Special"> &lt;- </span>subtract right:number, <span class="Constant">1:literal</span>
 <span class="CommentedCode">#?     $print [wrap? ], cursor-column:address:number/deref, [ vs ], wrap-column:number, [ </span>
 <span class="CommentedCode">#? ] #? 1</span>
@@ -782,24 +834,116 @@ container editor-data [
   <span class="muControl">reply</span> result:number
 ]
 
+<span class="muRecipe">recipe</span> render-all [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  env:address:programming-environment-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  recipes:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipes:offset
+  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, current-sandbox:offset
+  sandbox-in-focus?:boolean<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, sandbox-in-focus?:offset
+  <span class="Comment"># render recipes, along with any warnings</span>
+  left:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, left:offset
+  right:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, right:offset
+  row:number, screen:address<span class="Special"> &lt;- </span>render screen:address, recipes:address:editor-data
+  recipe-warnings:address:array:character<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipe-warnings:offset
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> recipe-warnings:address:array:character
+    row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, recipe-warnings:address:array:character, left:number, right:number, <span class="Constant">1:literal/red</span>, row:number
+  <span class="Delimiter">}</span>
+  <span class="Delimiter">{</span>
+    <span class="Comment"># no warnings? move to next lin</span>
+    <span class="muControl">break-if</span> recipe-warnings:address:array:character
+    row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># draw dotted line after recipes</span>
+  draw-horizontal screen:address, row:number, left:number, right:number, <span class="Constant">9480:literal/horizontal-dotted</span>
+  <span class="Comment"># clear next line, in case we just processed a backspace</span>
+  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+  move-cursor screen:address, row:number, left:number
+  clear-line-delimited screen:address, left:number, right:number
+  <span class="Comment"># render sandboxes along with warnings for each</span>
+  left:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, left:offset
+  right:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, right:offset
+  row:number, screen:address<span class="Special"> &lt;- </span>render screen:address, current-sandbox:address:editor-data
+  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+  draw-horizontal screen:address, row:number, left:number, right:number, <span class="Constant">9473:literal/horizontal-double</span>
+  sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, sandbox:offset
+  row:number, screen:address<span class="Special"> &lt;- </span>render-sandboxes screen:address, sandbox:address:sandbox-data, left:number, right:number, row:number
+  <span class="Comment"># clear next line, in case we just processed a backspace</span>
+  row:number<span class="Special"> &lt;- </span>add row:number, <span class="Constant">1:literal</span>
+  move-cursor screen:address, row:number, left:number
+  clear-line-delimited screen:address, left:number, right:number
+  update-cursor screen:address, recipes:address:editor-data, current-sandbox:address:editor-data, sandbox-in-focus?:boolean
+  show-screen screen:address
+  <span class="muControl">reply</span> screen:address/same-as-ingredient:0
+]
+
+<span class="muRecipe">recipe</span> render-sandboxes [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  sandbox:address:sandbox-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  left:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  row:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="muControl">reply-unless</span> sandbox:address:sandbox-data, row:number/same-as-ingredient:4, screen:address/same-as-ingredient:0
+  screen-height:number<span class="Special"> &lt;- </span>screen-width screen:address
+  at-bottom?:boolean<span class="Special"> &lt;- </span>greater-or-equal row:number screen-height:number
+  <span class="muControl">reply-if</span> at-bottom?:boolean, row:number/same-as-ingredient:4, screen:address/same-as-ingredient:0
+  <span class="Comment"># render sandbox contents</span>
+  sandbox-data:address:array:character<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, data:offset
+  row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, sandbox-data:address:array:character, left:number, right:number, <span class="Constant">7:literal/white</span>, row:number
+  <span class="Comment"># render sandbox warnings or response, in that order</span>
+  sandbox-response:address:array:character<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, response:offset
+  sandbox-warnings:address:array:character<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, warnings:offset
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> sandbox-warnings:address:array:character
+    row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, sandbox-warnings:address:array:character, left:number, right:number, <span class="Constant">1:literal/red</span>, row:number
+  <span class="Delimiter">}</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-if</span> sandbox-warnings:address:array:character
+    row:number, screen:address<span class="Special"> &lt;- </span>render-string screen:address, sandbox-response:address:array:character, left:number, right:number, <span class="Constant">245:literal/grey</span>, row:number
+  <span class="Delimiter">}</span>
+  <span class="Comment"># draw solid line after sandbox</span>
+  draw-horizontal screen:address, row:number, left:number, right:number, <span class="Constant">9473:literal/horizontal-double</span>
+  <span class="Comment"># draw next sandbox</span>
+  next-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>get sandbox:address:sandbox-data/deref, next-sandbox:offset
+  row:number, screen:address<span class="Special"> &lt;- </span>render-sandboxes screen:address, next-sandbox:address:sandbox-data, left:number, right:number, row:number
+  <span class="muControl">reply</span> row:number/same-as-ingredient:4, screen:address/same-as-ingredient:0
+]
+
+<span class="muRecipe">recipe</span> update-cursor [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">40:literal</span>
+  screen:address<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  recipes:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  current-sandbox:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  sandbox-in-focus?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-if</span> sandbox-in-focus?:boolean
+<span class="CommentedCode">#?     $print [recipes in focus</span>
+<span class="CommentedCode">#? ] #? 1</span>
+    cursor-row:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, cursor-row:offset
+    cursor-column:number<span class="Special"> &lt;- </span>get recipes:address:editor-data/deref, cursor-column:offset
+  <span class="Delimiter">}</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> sandbox-in-focus?:boolean
+<span class="CommentedCode">#?     $print [sandboxes in focus</span>
+<span class="CommentedCode">#? ] #? 1</span>
+    cursor-row:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, cursor-row:offset
+    cursor-column:number<span class="Special"> &lt;- </span>get current-sandbox:address:editor-data/deref, cursor-column:offset
+  <span class="Delimiter">}</span>
+  move-cursor screen:address, cursor-row:number, cursor-column:number
+]
+
 <span class="muScenario">scenario</span> editor-handles-empty-event-queue [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-<span class="CommentedCode">#?   3:number &lt;- get screen:address/deref, num-rows:offset #? 1</span>
-<span class="CommentedCode">#?   $print [0: ], screen:address, [: ], 3:number, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-<span class="CommentedCode">#?   $print [1: ], screen:address, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console <span class="Constant">[]</span>
-<span class="CommentedCode">#?   $print [8: ], screen:address, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
-<span class="CommentedCode">#?   $print [9: ], screen:address, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .          .</span>
   ]
@@ -808,21 +952,22 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 1  <span class="Comment"># on the 'b'</span>
+    left-click 1, 1  <span class="Comment"># on the 'b'</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .          .</span>
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor is at row 0..</span>
+    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor is at row 0..</span>
     4<span class="Special"> &lt;- </span>1  <span class="Comment"># ..and column 1</span>
   ]
 ]
@@ -830,17 +975,17 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-handles-mouse-clicks-outside-text [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 7  <span class="Comment"># last line, to the right of text</span>
+    left-click 1, 7  <span class="Comment"># last line, to the right of text</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor row</span>
+    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
     4<span class="Special"> &lt;- </span>3  <span class="Comment"># cursor column</span>
   ]
 ]
@@ -849,17 +994,17 @@ container editor-data [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 7  <span class="Comment"># interior line, to the right of text</span>
+    left-click 1, 7  <span class="Comment"># interior line, to the right of text</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor row</span>
+    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
     4<span class="Special"> &lt;- </span>3  <span class="Comment"># cursor column</span>
   ]
 ]
@@ -868,17 +1013,17 @@ container editor-data [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 2, 7  <span class="Comment"># below text</span>
+    left-click 3, 7  <span class="Comment"># below text</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
+    3<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor row</span>
     4<span class="Special"> &lt;- </span>3  <span class="Comment"># cursor column</span>
   ]
 ]
@@ -887,22 +1032,23 @@ container editor-data [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
   <span class="Comment"># editor occupies only left half of screen</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   assume-console [
     <span class="Comment"># click on right half of screen</span>
     left-click 3, 8
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .          .</span>
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0  <span class="Comment"># no change to cursor row</span>
+    3<span class="Special"> &lt;- </span>1  <span class="Comment"># no change to cursor row</span>
     4<span class="Special"> &lt;- </span>0  <span class="Comment"># ..or column</span>
   ]
 ]
@@ -910,14 +1056,15 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-inserts-characters-into-empty-editor [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   assume-console [
     type <span class="Constant">[abc]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .          .</span>
   ]
@@ -926,16 +1073,17 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
     type <span class="Constant">[0]</span>
-    left-click 0, 2
+    left-click 1, 2
     type <span class="Constant">[d]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .0adbc     .</span>
    <span class="Constant"> .          .</span>
   ]
@@ -944,15 +1092,16 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-2 [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 5  <span class="Comment"># right of last line</span>
+    left-click 1, 5  <span class="Comment"># right of last line</span>
     type <span class="Constant">[d]</span>  <span class="Comment"># should append</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd      .</span>
    <span class="Constant"> .          .</span>
   ]
@@ -961,15 +1110,16 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-3 [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
     left-click 3, 5  <span class="Comment"># below all text</span>
     type <span class="Constant">[d]</span>  <span class="Comment"># should append</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd      .</span>
    <span class="Constant"> .          .</span>
   ]
@@ -979,15 +1129,16 @@ container editor-data [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
     left-click 3, 5  <span class="Comment"># below all text</span>
     type <span class="Constant">[e]</span>  <span class="Comment"># should append</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .de        .</span>
    <span class="Constant"> .          .</span>
@@ -998,61 +1149,38 @@ container editor-data [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
     left-click 3, 5  <span class="Comment"># below all text</span>
     type <span class="Constant">[ef]</span>  <span class="Comment"># should append multiple characters in order</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .def       .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
 
-<span class="muScenario">scenario</span> editor-inserts-characters-at-cursor-6 [
-  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  <span class="Comment"># text fills line</span>
-  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
-  <span class="Comment"># position cursor at end</span>
-  assume-console [
-    left-click 3, 0
-  ]
-  run [
-    event-loop screen:address, console:address, 2:address:editor-data
-    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
-    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
-  ]
-  <span class="Comment"># text shouldn't wrap</span>
-  screen-should-contain [
-   <span class="Constant"> .abcde     .</span>
-   <span class="Constant"> .          .</span>
-  ]
-  <span class="Comment"># cursor should wrap</span>
-  memory-should-contain [
-    3<span class="Special"> &lt;- </span>1
-    4<span class="Special"> &lt;- </span>0
-  ]
-]
-
 <span class="muScenario">scenario</span> editor-wraps-line-on-insert [
-  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">3:literal/height</span>
-  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcd]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  assume-screen <span class="Constant">5:literal/width</span>, <span class="Constant">5:literal/height</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   <span class="Comment"># type a letter</span>
   assume-console [
     type <span class="Constant">[e]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   <span class="Comment"># no wrap yet</span>
   screen-should-contain [
-<span class="Constant">    .eabcd.</span>
+   <span class="Constant"> .     .</span>
+   <span class="Constant"> .eabc .</span>
+   <span class="Constant"> .     .</span>
    <span class="Constant"> .     .</span>
   ]
   <span class="Comment"># type a second letter</span>
@@ -1060,28 +1188,30 @@ container editor-data [
     type <span class="Constant">[f]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   <span class="Comment"># now wrap</span>
   screen-should-contain [
+   <span class="Constant"> .     .</span>
 <span class="Constant">    .efab↩.</span>
-   <span class="Constant"> .cd   .</span>
+   <span class="Constant"> .c    .</span>
    <span class="Constant"> .     .</span>
   ]
 ]
 
 <span class="muScenario">scenario</span> editor-moves-cursor-after-inserting-characters [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   assume-console [
     type <span class="Constant">[01]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
-   <span class="Constant"> .01abc     .</span>
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> .01ab      .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
@@ -1089,23 +1219,24 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-wraps-cursor-after-inserting-characters [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   assume-console [
-    left-click 0, 4  <span class="Comment"># line is full; no wrap icon yet</span>
+    left-click 1, 4  <span class="Comment"># line is full; no wrap icon yet</span>
     type <span class="Constant">[f]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd↩     .</span>
    <span class="Constant"> .fe        .</span>
    <span class="Constant"> .          .</span>
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
+    3<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor row</span>
     4<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor column</span>
   ]
 ]
@@ -1113,23 +1244,24 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-wraps-cursor-after-inserting-characters-2 [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   assume-console [
-    left-click 0, 3  <span class="Comment"># right before the wrap icon</span>
+    left-click 1, 3  <span class="Comment"># right before the wrap icon</span>
     type <span class="Constant">[f]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abcf↩     .</span>
    <span class="Constant"> .de        .</span>
    <span class="Constant"> .          .</span>
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>1  <span class="Comment"># cursor row</span>
+    3<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor row</span>
     4<span class="Special"> &lt;- </span>0  <span class="Comment"># cursor column</span>
   ]
 ]
@@ -1137,66 +1269,92 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
     type <span class="Constant">[0</span>
 <span class="Constant">1]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .0         .</span>
    <span class="Constant"> .1abc      .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
 
+<span class="muScenario">scenario</span> editor-moves-cursor-down-after-inserting-newline-2 [
+  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">10:literal/right</span>
+  assume-console [
+    type <span class="Constant">[0</span>
+<span class="Constant">1]</span>
+  ]
+  run [
+    editor-event-loop screen:address, console:address, 2:address:editor-data
+  ]
+  screen-should-contain [
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> . 0        .</span>
+   <span class="Constant"> . 1abc     .</span>
+   <span class="Constant"> .          .</span>
+  ]
+]
+
 <span class="muScenario">scenario</span> editor-clears-previous-line-completely-after-inserting-newline [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   <span class="Comment"># press just a 'newline'</span>
   assume-console [
     type [
 ]
   ]
+  screen-should-contain [
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> .abcd↩     .</span>
+   <span class="Constant"> .e         .</span>
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> .          .</span>
+  ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   <span class="Comment"># line should be fully cleared</span>
   screen-should-contain [
    <span class="Constant"> .          .</span>
-   <span class="Constant"> .abcde     .</span>
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> .abcd↩     .</span>
+   <span class="Constant"> .e         .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
 
 <span class="muScenario">scenario</span> editor-handles-backspace-key [
-<span class="CommentedCode">#?   $print [=== new test</span>
-<span class="CommentedCode">#? ] #? 1</span>
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
-<span class="CommentedCode">#?   $print [editor: ], 2:address:editor-data, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 1
+    left-click 1, 1
     type <span class="Constant">[«]</span>
   ]
   3:event/backspace<span class="Special"> &lt;- </span>merge <span class="Constant">0:literal/text</span>, <span class="Constant">8:literal/backspace</span>, <span class="Constant">0:literal/dummy</span>, <span class="Constant">0:literal/dummy</span>
   replace-in-console <span class="Constant">171:literal/«</span>, 3:event/backspace
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     5:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .bc        .</span>
    <span class="Constant"> .          .</span>
   ]
   memory-should-contain [
-    4<span class="Special"> &lt;- </span>0
+    4<span class="Special"> &lt;- </span>1
     5<span class="Special"> &lt;- </span>0
   ]
 ]
@@ -1204,87 +1362,71 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-clears-last-line-on-backspace [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   <span class="Comment"># just one character in final line</span>
-  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
-<span class="Constant">d]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
+<span class="Constant">cd]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   assume-console [
-    left-click 1, 0  <span class="Comment"># cursor at only character in final line</span>
+    left-click 2, 0  <span class="Comment"># cursor at only character in final line</span>
     type <span class="Constant">[«]</span>
   ]
   3:event/backspace<span class="Special"> &lt;- </span>merge <span class="Constant">0:literal/text</span>, <span class="Constant">8:literal/backspace</span>, <span class="Constant">0:literal/dummy</span>, <span class="Constant">0:literal/dummy</span>
   replace-in-console <span class="Constant">171:literal/«</span>, 3:event/backspace
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd      .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
 
-<span class="muScenario">scenario</span> editor-handles-backspace-key-at-right-margin [
+<span class="muScenario">scenario</span> editor-moves-cursor-right-with-key [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  <span class="Comment"># fill a line with text</span>
-  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
-  <span class="Comment"># position cursor at end</span>
-  assume-console [
-    left-click 1, 3  <span class="Comment"># at end of text</span>
-  ]
-  run [
-    event-loop screen:address, console:address, 2:address:editor-data
-    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
-    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
-  ]
-  <span class="Comment"># check that cursor wraps to next line</span>
-  memory-should-contain [
-    3<span class="Special"> &lt;- </span>1
-    4<span class="Special"> &lt;- </span>0
-  ]
-  <span class="Comment"># now hit a backspace key</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    type <span class="Constant">[«]</span>
+    press 65514  <span class="Comment"># right arrow</span>
+    type <span class="Constant">[0]</span>
   ]
-  5:event/backspace<span class="Special"> &lt;- </span>merge <span class="Constant">0:literal/text</span>, <span class="Constant">8:literal/backspace</span>, <span class="Constant">0:literal/dummy</span>, <span class="Constant">0:literal/dummy</span>
-  replace-in-console <span class="Constant">171:literal/«</span>, 5:event/backspace
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
-    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
-    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
-  ]
-  <span class="Comment"># cursor unwraps</span>
-  memory-should-contain [
-    3<span class="Special"> &lt;- </span>0
-    4<span class="Special"> &lt;- </span>4
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
-   <span class="Constant"> .abcd      .</span>
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> .a0bc      .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
 
-<span class="muScenario">scenario</span> editor-moves-cursor-right-with-key [
+<span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
+<span class="Constant">d]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
     press 65514  <span class="Comment"># right arrow</span>
+    press 65514  <span class="Comment"># right arrow</span>
+    press 65514  <span class="Comment"># right arrow</span>
+    press 65514  <span class="Comment"># right arrow - next line</span>
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
-   <span class="Constant"> .a0bc      .</span>
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> .abc       .</span>
+   <span class="Constant"> .0d        .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
 
-<span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow [
+<span class="muScenario">scenario</span> editor-moves-cursor-to-next-line-with-right-arrow-2 [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
     press 65514  <span class="Comment"># right arrow</span>
     press 65514  <span class="Comment"># right arrow</span>
@@ -1293,11 +1435,12 @@ container editor-data [
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
-   <span class="Constant"> .abc       .</span>
-   <span class="Constant"> .0d        .</span>
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> . abc      .</span>
+   <span class="Constant"> . 0d       .</span>
    <span class="Constant"> .          .</span>
   ]
 ]
@@ -1305,63 +1448,84 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   assume-console [
-    left-click 0, 3
+    left-click 1, 3
     press 65514  <span class="Comment"># right arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd↩     .</span>
    <span class="Constant"> .ef        .</span>
    <span class="Constant"> .          .</span>
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>1
+    3<span class="Special"> &lt;- </span>2
     4<span class="Special"> &lt;- </span>0
   ]
 ]
 
-<span class="muScenario">scenario</span> editor-does-not-wrap-cursor-when-line-does-not-wrap [
+<span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow-2 [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
+  <span class="Comment"># line just barely wrapping</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  <span class="Comment"># position cursor at last character before wrap and hit right-arrow</span>
   assume-console [
-    left-click 0, 3  <span class="Comment"># one before right, in the last line</span>
+    left-click 1, 3
     press 65514  <span class="Comment"># right arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
+    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
+    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
+  ]
+  memory-should-contain [
+    3<span class="Special"> &lt;- </span>2
+    4<span class="Special"> &lt;- </span>0
+  ]
+  <span class="Comment"># now hit right arrow again</span>
+  assume-console [
+    press 65514
+  ]
+  run [
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0
-    4<span class="Special"> &lt;- </span>4
+    3<span class="Special"> &lt;- </span>2
+    4<span class="Special"> &lt;- </span>1
   ]
 ]
 
-<span class="muScenario">scenario</span> editor-does-not-wrap-cursor-when-line-does-not-wrap-2 [
+<span class="muScenario">scenario</span> editor-moves-cursor-to-next-wrapped-line-with-right-arrow-3 [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcde</span>
-<span class="Constant">f]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">1:literal/left</span>, <span class="Constant">6:literal/right</span>
   assume-console [
-    left-click 0, 3  <span class="Comment"># one before right, not the last line</span>
+    left-click 1, 4
     press 65514  <span class="Comment"># right arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
+  screen-should-contain [
+   <span class="Constant"> .          .</span>
+   <span class="Constant"> . abcd↩    .</span>
+   <span class="Constant"> . ef       .</span>
+   <span class="Constant"> .          .</span>
+  ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0
-    4<span class="Special"> &lt;- </span>4
+    3<span class="Special"> &lt;- </span>2
+    4<span class="Special"> &lt;- </span>1
   ]
 ]
 
@@ -1369,16 +1533,17 @@ container editor-data [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 3
+    left-click 1, 3
     press 65514  <span class="Comment"># right arrow - next line</span>
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .0d        .</span>
    <span class="Constant"> .          .</span>
@@ -1388,16 +1553,17 @@ container editor-data [
 <span class="muScenario">scenario</span> editor-moves-cursor-left-with-key [
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 2
+    left-click 1, 2
     press 65515  <span class="Comment"># left arrow</span>
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .a0bc      .</span>
    <span class="Constant"> .          .</span>
   ]
@@ -1408,20 +1574,20 @@ container editor-data [
   <span class="Comment"># initialize editor with two lines</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">d]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   <span class="Comment"># position cursor at start of second line (so there's no previous newline)</span>
   assume-console [
-    left-click 1, 0
+    left-click 2, 0
     press 65515  <span class="Comment"># left arrow</span>
-    type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
+    3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
+    4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
-  screen-should-contain [
-   <span class="Constant"> .abc0      .</span>
-   <span class="Constant"> .d         .</span>
-   <span class="Constant"> .          .</span>
+  memory-should-contain [
+    3<span class="Special"> &lt;- </span>1
+    4<span class="Special"> &lt;- </span>3
   ]
 ]
 
@@ -1431,18 +1597,19 @@ container editor-data [
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">g]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   <span class="Comment"># position cursor further down (so there's a newline before the character at</span>
   <span class="Comment"># the cursor)</span>
   assume-console [
-    left-click 2, 0
+    left-click 3, 0
     press 65515  <span class="Comment"># left arrow</span>
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .def0      .</span>
    <span class="Constant"> .g         .</span>
@@ -1455,17 +1622,18 @@ container editor-data [
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def</span>
 <span class="Constant">g]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   <span class="Comment"># position cursor at start of text</span>
   assume-console [
-    left-click 0, 0
+    left-click 1, 0
     press 65515  <span class="Comment"># left arrow should have no effect</span>
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .0abc      .</span>
    <span class="Constant"> .def       .</span>
    <span class="Constant"> .g         .</span>
@@ -1479,17 +1647,18 @@ container editor-data [
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 
 d]
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   <span class="Comment"># position cursor right after empty line</span>
   assume-console [
-    left-click 2, 0
+    left-click 3, 0
     press 65515  <span class="Comment"># left arrow</span>
     type <span class="Constant">[0]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
   ]
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abc       .</span>
    <span class="Constant"> .0         .</span>
    <span class="Constant"> .d         .</span>
@@ -1501,24 +1670,25 @@ d]
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   <span class="Comment"># initialize editor with text containing an empty line</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abcdef]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
   screen-should-contain [
+   <span class="Constant"> .          .</span>
    <span class="Constant"> .abcd↩     .</span>
    <span class="Constant"> .ef        .</span>
    <span class="Constant"> .          .</span>
   ]
   <span class="Comment"># position cursor right after empty line</span>
   assume-console [
-    left-click 1, 0
+    left-click 2, 0
     press 65515  <span class="Comment"># left arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0  <span class="Comment"># previous row</span>
+    3<span class="Special"> &lt;- </span>1  <span class="Comment"># previous row</span>
     4<span class="Special"> &lt;- </span>3  <span class="Comment"># end of wrapped line</span>
   ]
 ]
@@ -1527,18 +1697,18 @@ d]
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 1, 1
+    left-click 2, 1
     press 65517  <span class="Comment"># up arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0
+    3<span class="Special"> &lt;- </span>1
     4<span class="Special"> &lt;- </span>1
   ]
 ]
@@ -1547,19 +1717,19 @@ d]
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">def]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
-  <span class="Comment"># cursor starts out at (0, 0)</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  <span class="Comment"># cursor starts out at (1, 0)</span>
   assume-console [
     press 65516  <span class="Comment"># down arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
-  <span class="Comment"># ..and ends at (1, 0)</span>
+  <span class="Comment"># ..and ends at (2, 0)</span>
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>1
+    3<span class="Special"> &lt;- </span>2
     4<span class="Special"> &lt;- </span>0
   ]
 ]
@@ -1568,18 +1738,18 @@ d]
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ab</span>
 <span class="Constant">def]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 1, 3
+    left-click 2, 3
     press 65517  <span class="Comment"># up arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>0
+    3<span class="Special"> &lt;- </span>1
     4<span class="Special"> &lt;- </span>2
   ]
 ]
@@ -1588,164 +1758,402 @@ d]
   assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc</span>
 <span class="Constant">de]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
   assume-console [
-    left-click 0, 3
+    left-click 1, 3
     press 65516  <span class="Comment"># down arrow</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    editor-event-loop screen:address, console:address, 2:address:editor-data
     3:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
     4:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
-    3<span class="Special"> &lt;- </span>1
+    3<span class="Special"> &lt;- </span>2
     4<span class="Special"> &lt;- </span>2
   ]
 ]
 
 <span class="muScenario">scenario</span> point-at-multiple-editors [
-  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  <span class="Comment"># initialize an editor covering left half of screen</span>
+  assume-screen <span class="Constant">30:literal/width</span>, <span class="Constant">5:literal/height</span>
+  <span class="Comment"># initialize both halves of screen</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
-  3:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-  <span class="Comment"># chain new editor to it, covering the right half of the screen</span>
-  4:address:address:editor-data<span class="Special"> &lt;- </span>get-address 2:address:editor-data/deref, next-editor:offset
-  4:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor 3:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">5:literal/left</span>, <span class="Constant">10:literal/right</span>
-  <span class="Comment"># type one letter in each of them</span>
+  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
+  <span class="Comment"># focus on both sides</span>
   assume-console [
-    left-click 0, 1
-    left-click 0, 8
+    left-click 1, 1
+    left-click 1, 17
   ]
+  <span class="Comment"># check cursor column in each</span>
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
-    5:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
-    6:number<span class="Special"> &lt;- </span>get 4:address:address:editor-data/deref/deref, cursor-column:offset
+    event-loop screen:address, console:address, 3:address:programming-environment-data
+    4:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, recipes:offset
+    5:number<span class="Special"> &lt;- </span>get 4:address:editor-data/deref, cursor-column:offset
+    6:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, current-sandbox:offset
+    7:number<span class="Special"> &lt;- </span>get 6:address:editor-data/deref, cursor-column:offset
   ]
   memory-should-contain [
     5<span class="Special"> &lt;- </span>1
-    6<span class="Special"> &lt;- </span>8
+    7<span class="Special"> &lt;- </span>17
   ]
 ]
 
-<span class="muScenario">scenario</span> editors-chain-to-cover-multiple-columns [
-  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  <span class="Comment"># initialize an editor covering left half of screen</span>
+<span class="muScenario">scenario</span> edit-multiple-editors [
+  assume-screen <span class="Constant">30:literal/width</span>, <span class="Constant">5:literal/height</span>
+  <span class="Comment"># initialize both halves of screen</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
-  3:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-  <span class="Comment"># chain new editor to it, covering the right half of the screen</span>
-  4:address:address:editor-data<span class="Special"> &lt;- </span>get-address 2:address:editor-data/deref, next-editor:offset
-  4:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor 3:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">5:literal/left</span>, <span class="Constant">10:literal/right</span>
-  reset-focus 2:address:editor-data
+  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
   <span class="Comment"># type one letter in each of them</span>
   assume-console [
-    left-click 0, 1
+    left-click 1, 1
     type <span class="Constant">[0]</span>
-    left-click 0, 6
+    left-click 1, 17
     type <span class="Constant">[1]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
-    5:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
-    6:number<span class="Special"> &lt;- </span>get 4:address:address:editor-data/deref/deref, cursor-column:offset
+    event-loop screen:address, console:address, 3:address:programming-environment-data
+    4:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, recipes:offset
+    5:number<span class="Special"> &lt;- </span>get 4:address:editor-data/deref, cursor-column:offset
+    6:address:editor-data<span class="Special"> &lt;- </span>get 3:address:programming-environment-data/deref, current-sandbox:offset
+    7:number<span class="Special"> &lt;- </span>get 6:address:editor-data/deref, cursor-column:offset
   ]
   screen-should-contain [
-   <span class="Constant"> .a0bc d1ef .</span>
-   <span class="Constant"> .          .</span>
+   <span class="Constant"> .           run (F10)          .  # this line has a different background, but we don't test that yet</span>
+   <span class="Constant"> .a0bc           ┊d1ef          .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
   ]
   memory-should-contain [
-    5<span class="Special"> &lt;- </span>2
-    6<span class="Special"> &lt;- </span>7
+    5<span class="Special"> &lt;- </span>2  <span class="Comment"># cursor column of recipe editor</span>
+    7<span class="Special"> &lt;- </span>18  <span class="Comment"># cursor column of sandbox editor</span>
   ]
   <span class="Comment"># show the cursor at the right window</span>
   run [
     screen:address<span class="Special"> &lt;- </span>print-character screen:address, <span class="Constant">9251:literal/␣</span>
   ]
   screen-should-contain [
-   <span class="Constant"> .a0bc d1␣f .</span>
-   <span class="Constant"> .          .</span>
+   <span class="Constant"> .           run (F10)          .</span>
+   <span class="Constant"> .a0bc           ┊d1␣f          .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
   ]
 ]
 
 <span class="muScenario">scenario</span> multiple-editors-cover-only-their-own-areas [
-  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
+  assume-screen <span class="Constant">60:literal/width</span>, <span class="Constant">10:literal/height</span>
   run [
-    <span class="Comment"># draw a divider</span>
-    draw-vertical screen:address, <span class="Constant">5:literal/divider</span>, <span class="Constant">0:literal/top</span>, <span class="Constant">5:literal/height</span>
-    <span class="Comment"># initialize editors on both sides of it and chain the two</span>
     1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-    2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
-    3:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-    4:address:address:editor-data<span class="Special"> &lt;- </span>get-address 2:address:editor-data/deref, next-editor:offset
-    4:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor 3:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">6:literal/left</span>, <span class="Constant">10:literal/right</span>
+    2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+    3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
   ]
   <span class="Comment"># divider isn't messed up</span>
   screen-should-contain [
-   <span class="Constant"> .abc  │def .</span>
-   <span class="Constant"> .     │    .</span>
-   <span class="Constant"> .     │    .</span>
-   <span class="Constant"> .     │    .</span>
-   <span class="Constant"> .     │    .</span>
+   <span class="Constant"> .                                         run (F10)          .</span>
+   <span class="Constant"> .abc                           ┊def                          .</span>
+   <span class="Constant"> .                              ┊                             .</span>
+   <span class="Constant"> .                              ┊                             .</span>
+   <span class="Constant"> .                              ┊                             .</span>
   ]
 ]
 
 <span class="muScenario">scenario</span> editor-in-focus-keeps-cursor [
-  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
-  <span class="Comment"># initialize an editor covering left half of screen</span>
+  assume-screen <span class="Constant">30:literal/width</span>, <span class="Constant">5:literal/height</span>
   1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
-  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">0:literal/left</span>, <span class="Constant">5:literal/right</span>
-  3:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
-  <span class="Comment"># chain new editor to it, covering the right half of the screen</span>
-  4:address:address:editor-data<span class="Special"> &lt;- </span>get-address 2:address:editor-data/deref, next-editor:offset
-  4:address:address:editor-data/deref<span class="Special"> &lt;- </span>new-editor 3:address:array:character, screen:address, <span class="Constant">0:literal/top</span>, <span class="Constant">5:literal/left</span>, <span class="Constant">10:literal/right</span>
-  <span class="Comment"># initialize cursor</span>
+  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[def]</span>
+  <span class="Comment"># initialize programming environment and highlight cursor</span>
+  assume-console <span class="Constant">[]</span>
   run [
-    reset-focus 2:address:editor-data
-    5:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-row:offset
-    6:number<span class="Special"> &lt;- </span>get 2:address:editor-data/deref, cursor-column:offset
-    move-cursor screen:address, 5:number, 6:number
+    3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
+    event-loop screen:address, console:address, 3:address:programming-environment-data
     screen:address<span class="Special"> &lt;- </span>print-character screen:address, <span class="Constant">9251:literal/␣</span>
   ]
-  <span class="Comment"># is it at the right place?</span>
+  <span class="Comment"># is cursor at the right place?</span>
   screen-should-contain [
-   <span class="Constant"> .␣bc  def  .</span>
-   <span class="Constant"> .          .</span>
+   <span class="Constant"> .           run (F10)          .</span>
+   <span class="Constant"> .␣bc            ┊def           .</span>
+<span class="Comment"># artifact of fake console: no events = no render</span>
+<span class="Comment">#   .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
   ]
   <span class="Comment"># now try typing a letter</span>
   assume-console [
     type <span class="Constant">[z]</span>
   ]
   run [
-    event-loop screen:address, console:address, 2:address:editor-data
+    3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
+    event-loop screen:address, console:address, 3:address:programming-environment-data
     screen:address<span class="Special"> &lt;- </span>print-character screen:address, <span class="Constant">9251:literal/␣</span>
   ]
   <span class="Comment"># cursor should still be right</span>
   screen-should-contain [
-   <span class="Constant"> .z␣bc def  .</span>
-   <span class="Constant"> .          .</span>
+   <span class="Constant"> .           run (F10)          .</span>
+   <span class="Constant"> .z␣bc           ┊def           .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .               ┊              .</span>
+  ]
+]
+
+<span class="SalientComment">## Running code from the editors</span>
+
+container sandbox-data [
+  data:address:array:character
+  response:address:array:character
+  warnings:address:array:character
+  next-sandbox:address:sandbox-data
+]
+
+<span class="muScenario">scenario</span> run-and-show-results [
+  $close-trace  <span class="Comment"># trace too long for github</span>
+  assume-screen <span class="Constant">100:literal/width</span>, <span class="Constant">12:literal/height</span>
+  <span class="Comment"># recipe editor is empty</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
+  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[divide-with-remainder 11:literal, 3:literal]</span>
+  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
+  <span class="Comment"># run the code in the editors</span>
+  assume-console [
+    press 65526  <span class="Comment"># F10</span>
+  ]
+  run [
+    event-loop screen:address, console:address, 3:address:programming-environment-data
+  ]
+  <span class="Comment"># check that screen prints the results</span>
+  screen-should-contain [
+   <span class="Constant"> .                                                                                 run (F10)          .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊divide-with-remainder 11:literal, 3:literal      .</span>
+   <span class="Constant"> .                                                  ┊3                                                .</span>
+   <span class="Constant"> .                                                  ┊2                                                .</span>
+   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+  ]
+  screen-should-contain-in-color <span class="Constant">7:literal/white</span>, [
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                   divide-with-remainder 11:literal, 3:literal      .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+  ]
+  screen-should-contain-in-color, <span class="Constant">245:literal/grey</span>, [
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+   <span class="Constant"> .                                                  ┊3                                                .</span>
+   <span class="Constant"> .                                                  ┊2                                                .</span>
+   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+  ]
+  <span class="Comment"># run another command</span>
+  assume-console [
+    left-click 1, 80
+    type <span class="Constant">[add 2:literal, 2:literal]</span>
+    press 65526  <span class="Comment"># F10</span>
+  ]
+  run [
+    event-loop screen:address, console:address, 3:address:programming-environment-data
+  ]
+  <span class="Comment"># check that screen prints the results</span>
+  screen-should-contain [
+   <span class="Constant"> .                                                                                 run (F10)          .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊add 2:literal, 2:literal                         .</span>
+   <span class="Constant"> .                                                  ┊4                                                .</span>
+   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊divide-with-remainder 11:literal, 3:literal      .</span>
+   <span class="Constant"> .                                                  ┊3                                                .</span>
+   <span class="Constant"> .                                                  ┊2                                                .</span>
+   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+  ]
+]
+
+<span class="muRecipe">recipe</span> run-sandboxes [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
+  env:address:programming-environment-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  recipes:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, recipes:offset
+  current-sandbox:address:editor-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, current-sandbox:offset
+  <span class="Comment"># load code from recipe editor, save any warnings</span>
+  in:address:array:character<span class="Special"> &lt;- </span>editor-contents recipes:address:editor-data
+  recipe-warnings:address:address:array:character<span class="Special"> &lt;- </span>get-address env:address:programming-environment-data/deref, recipe-warnings:offset
+  recipe-warnings:address:address:array:character/deref<span class="Special"> &lt;- </span>reload in:address:array:character
+  <span class="Comment"># check contents of right editor (sandbox)</span>
+  <span class="Delimiter">{</span>
+    sandbox-contents:address:array:character<span class="Special"> &lt;- </span>editor-contents current-sandbox:address:editor-data
+    <span class="muControl">break-unless</span> sandbox-contents:address:array:character
+    <span class="Comment"># if contents exist, run them and turn them into a new sandbox-data</span>
+    new-sandbox:address:sandbox-data<span class="Special"> &lt;- </span>new sandbox-data:type
+    data:address:address:array:character<span class="Special"> &lt;- </span>get-address new-sandbox:address:sandbox-data/deref, data:offset
+    data:address:address:array:character/deref<span class="Special"> &lt;- </span>copy sandbox-contents:address:array:character
+    <span class="Comment"># push to head of sandbox list</span>
+    dest:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address env:address:programming-environment-data/deref, sandbox:offset
+    next:address:address:sandbox-data<span class="Special"> &lt;- </span>get-address new-sandbox:address:sandbox-data/deref, next-sandbox:offset
+    next:address:address:sandbox-data/deref<span class="Special"> &lt;- </span>copy dest:address:address:sandbox-data/deref
+    dest:address:address:sandbox-data/deref<span class="Special"> &lt;- </span>copy new-sandbox:address:sandbox-data
+    <span class="Comment"># clear sandbox editor</span>
+    init:address:address:duplex-list<span class="Special"> &lt;- </span>get-address current-sandbox:address:editor-data/deref, data:offset
+    init:address:address:duplex-list/deref<span class="Special"> &lt;- </span>push-duplex <span class="Constant">167:literal/§</span>, <span class="Constant">0:literal/tail</span>
+  <span class="Delimiter">}</span>
+  <span class="Comment"># rerun other sandboxes</span>
+  curr:address:sandbox-data<span class="Special"> &lt;- </span>get env:address:programming-environment-data/deref, sandbox:offset
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-unless</span> curr:address:sandbox-data
+    data:address:address:array:character<span class="Special"> &lt;- </span>get-address curr:address:sandbox-data/deref, data:offset
+    response:address:address:array:character<span class="Special"> &lt;- </span>get-address curr:address:sandbox-data/deref, response:offset
+    warnings:address:address:array:character<span class="Special"> &lt;- </span>get-address curr:address:sandbox-data/deref, warnings:offset
+    response:address:address:array:character/deref, warnings:address:address:array:character/deref<span class="Special"> &lt;- </span>run-interactive data:address:address:array:character/deref
+    curr:address:sandbox-data<span class="Special"> &lt;- </span>get curr:address:sandbox-data/deref, next-sandbox:offset
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+]
+
+<span class="muScenario">scenario</span> run-updates-results [
+  $close-trace  <span class="Comment"># trace too long for github</span>
+  assume-screen <span class="Constant">100:literal/width</span>, <span class="Constant">12:literal/height</span>
+  <span class="Comment"># define a recipe (no indent for the 'add' line below so column numbers are more obvious)</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[ </span>
+<span class="Constant">recipe foo [</span>
+<span class="Constant">z:number &lt;- add 2:literal, 2:literal</span>
+<span class="Constant">]</span>]
+  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
+  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[foo]</span>
+  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
+  <span class="Comment"># run the code in the editors</span>
+  assume-console [
+    press 65526  <span class="Comment"># F10</span>
+  ]
+  run [
+    event-loop screen:address, console:address, 3:address:programming-environment-data
+  ]
+  <span class="Comment"># check that screen prints the results</span>
+  screen-should-contain [
+   <span class="Constant"> .                                                                                 run (F10)          .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+   <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .z:number &lt;- add 2:literal, 2:literal              ┊foo                                              .</span>
+   <span class="Constant"> .]                                                 ┊4                                                .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+  ]
+  <span class="Comment"># make a change (incrementing one of the args to 'add'), then rerun</span>
+  assume-console [
+    left-click 3, 28  <span class="Comment"># one past the value of the second arg</span>
+    type <span class="Constant">[«3]</span>  <span class="Comment"># replace</span>
+    press 65526  <span class="Comment"># F10</span>
+  ]
+  4:event/backspace<span class="Special"> &lt;- </span>merge <span class="Constant">0:literal/text</span>, <span class="Constant">8:literal/backspace</span>, <span class="Constant">0:literal/dummy</span>, <span class="Constant">0:literal/dummy</span>
+  replace-in-console <span class="Constant">171:literal/«</span>, 4:event/backspace
+  run [
+    event-loop screen:address, console:address, 3:address:programming-environment-data
+  ]
+  <span class="Comment"># check that screen updates the result on the right</span>
+  screen-should-contain [
+   <span class="Constant"> .                                                                                 run (F10)          .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+   <span class="Constant"> .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .z:number &lt;- add 2:literal, 3:literal              ┊foo                                              .</span>
+   <span class="Constant"> .]                                                 ┊5                                                .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
   ]
 ]
 
-<span class="Comment"># set focus to first editor, reset it in later ones</span>
-<span class="muRecipe">recipe</span> reset-focus [
+<span class="muScenario">scenario</span> run-instruction-and-print-warnings [
+  $close-trace  <span class="Comment"># trace too long for github</span>
+  assume-screen <span class="Constant">100:literal/width</span>, <span class="Constant">10:literal/height</span>
+  <span class="Comment"># left editor is empty</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[]</span>
+  <span class="Comment"># right editor contains an illegal instruction</span>
+  2:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[get 1234:number, foo:offset]</span>
+  3:address:programming-environment-data<span class="Special"> &lt;- </span>new-programming-environment screen:address, 1:address:array:character, 2:address:array:character
+  <span class="Comment"># run the code in the editors</span>
+  assume-console [
+    press 65526  <span class="Comment"># F10</span>
+  ]
+  run [
+    event-loop screen:address, console:address, 3:address:programming-environment-data
+  ]
+  <span class="Comment"># check that screen prints error message in red</span>
+  screen-should-contain [
+   <span class="Constant"> .                                                                                 run (F10)          .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊get 1234:number, foo:offset                      .</span>
+   <span class="Constant"> .                                                  ┊unknown element foo in container number          .</span>
+   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+  ]
+  screen-should-contain-in-color <span class="Constant">7:literal/white</span>, [
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                   get 1234:number, foo:offset                      .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+  ]
+  screen-should-contain-in-color, <span class="Constant">1:literal/red</span>, [
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                   unknown element foo in container number          .</span>
+   <span class="Constant"> .                                                                                                    .</span>
+  ]
+  screen-should-contain-in-color, <span class="Constant">245:literal/grey</span>, [
+   <span class="Constant"> .                                                                                                    .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+<span class="Constant">    .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+   <span class="Constant"> .                                                  ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.</span>
+   <span class="Constant"> .                                                  ┊                                                 .</span>
+  ]
+]
+
+<span class="muRecipe">recipe</span> editor-contents [
   <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
   editor:address:editor-data<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
-  in-focus:address:boolean<span class="Special"> &lt;- </span>get-address editor:address:editor-data/deref, in-focus?:offset
-  in-focus:address:boolean/deref<span class="Special"> &lt;- </span>copy <span class="Constant">1:literal/true</span>
-  e:address:editor-data<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, next-editor:offset
+  buf:address:buffer<span class="Special"> &lt;- </span>new-buffer <span class="Constant">80:literal</span>
+  curr:address:duplex-list<span class="Special"> &lt;- </span>get editor:address:editor-data/deref, data:offset
+  <span class="Comment"># skip § sentinel</span>
+  assert curr:address:duplex-list, <span class="Constant">[editor without data is illegal; must have at least a sentinel]</span>
+  curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
+  <span class="muControl">reply-unless</span> curr:address:duplex-list, <span class="Constant">0:literal</span>
   <span class="Delimiter">{</span>
-    <span class="muControl">break-unless</span> e:address:editor-data
-<span class="CommentedCode">#?     $print [resetting focus in ], e:address:editor-data, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-    x:address:boolean<span class="Special"> &lt;- </span>get-address e:address:editor-data/deref, in-focus?:offset
-<span class="CommentedCode">#?     $print [ at ], x:address:boolean, [ </span>
-<span class="CommentedCode">#? ] #? 1</span>
-    x:address:boolean/deref<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal/false</span>
-    e:address:editor-data<span class="Special"> &lt;- </span>get e:address:editor-data/deref, next-editor:offset
+    <span class="muControl">break-unless</span> curr:address:duplex-list
+    c:character<span class="Special"> &lt;- </span>get curr:address:duplex-list/deref, value:offset
+    buffer-append buf:address:buffer, c:character
+    curr:address:duplex-list<span class="Special"> &lt;- </span>next-duplex curr:address:duplex-list
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
+  result:address:array:character<span class="Special"> &lt;- </span>buffer-to-array buf:address:buffer
+  <span class="muControl">reply</span> result:address:array:character
+]
+
+<span class="muScenario">scenario</span> editor-provides-edited-contents [
+  assume-screen <span class="Constant">10:literal/width</span>, <span class="Constant">5:literal/height</span>
+  1:address:array:character<span class="Special"> &lt;- </span>new <span class="Constant">[abc]</span>
+  2:address:editor-data<span class="Special"> &lt;- </span>new-editor 1:address:array:character, screen:address, <span class="Constant">0:literal/left</span>, <span class="Constant">10:literal/right</span>
+  assume-console [
+    left-click 1, 2
+    type <span class="Constant">[def]</span>
+  ]
+  run [
+    editor-event-loop screen:address, console:address, 2:address:editor-data
+    3:address:array:character<span class="Special"> &lt;- </span>editor-contents 2:address:editor-data
+    4:array:character<span class="Special"> &lt;- </span>copy 3:address:array:character/deref
+  ]
+  memory-should-contain [
+    4:string<span class="Special"> &lt;- </span><span class="Constant">[abdefc]</span>
+  ]
 ]
 
 <span class="SalientComment">## helpers for drawing editor borders</span>
@@ -1784,17 +2192,27 @@ d]
   row:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   x:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   right:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  style:character, style-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-if</span> style-found?:boolean
+    style:character<span class="Special"> &lt;- </span>copy <span class="Constant">9472:literal/horizontal</span>
+  <span class="Delimiter">}</span>
   color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># default color to white</span>
     <span class="muControl">break-if</span> color-found?:boolean
     color:number<span class="Special"> &lt;- </span>copy <span class="Constant">245:literal/grey</span>
   <span class="Delimiter">}</span>
+  bg-color:number, bg-color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-if</span> bg-color-found?:boolean
+    bg-color:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal/black</span>
+  <span class="Delimiter">}</span>
   move-cursor screen:address, row:number, x:number
   <span class="Delimiter">{</span>
-    continue?:boolean<span class="Special"> &lt;- </span>lesser-than x:number, right:number
+    continue?:boolean<span class="Special"> &lt;- </span>lesser-or-equal x:number, right:number  <span class="Comment"># right is inclusive, to match editor-data semantics</span>
     <span class="muControl">break-unless</span> continue?:boolean
-    print-character screen:address, <span class="Constant">9472:literal/horizontal</span>, color:number
+    print-character screen:address, style:character, color:number, bg-color:number
     x:number<span class="Special"> &lt;- </span>add x:number, <span class="Constant">1:literal</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
@@ -1806,6 +2224,11 @@ d]
   col:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   x:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   bottom:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  style:character, style-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  <span class="Delimiter">{</span>
+    <span class="muControl">break-if</span> style-found?:boolean
+    style:character<span class="Special"> &lt;- </span>copy <span class="Constant">9474:literal/vertical</span>
+  <span class="Delimiter">}</span>
   color:number, color-found?:boolean<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
   <span class="Delimiter">{</span>
     <span class="Comment"># default color to white</span>
@@ -1816,7 +2239,7 @@ d]
     continue?:boolean<span class="Special"> &lt;- </span>lesser-than x:number, bottom:number
     <span class="muControl">break-unless</span> continue?:boolean
     move-cursor screen:address, x:number, col:number
-    print-character screen:address, <span class="Constant">9474:literal/vertical</span>, color:number
+    print-character screen:address, style:character, color:number
     x:number<span class="Special"> &lt;- </span>add x:number, <span class="Constant">1:literal</span>
     <span class="muControl">loop</span>
   <span class="Delimiter">}</span>
@@ -1881,6 +2304,37 @@ d]
   move-cursor screen:address, bottom:number, right:number
   print-character screen:address, <span class="Constant">9496:literal/up-left</span>, color:number
 ]
+
+<span class="muRecipe">recipe</span> print-string-with-gradient-background [
+  <span class="Constant">default-space</span>:address:array:location<span class="Special"> &lt;- </span>new location:type, <span class="Constant">30:literal</span>
+  x:address:screen<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  s:address:array:character<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  color:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  bg-color1:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  bg-color2:number<span class="Special"> &lt;- </span><span class="Constant">next-ingredient</span>
+  len:number<span class="Special"> &lt;- </span>length s:address:array:character/deref
+  color-range:number<span class="Special"> &lt;- </span>subtract bg-color2:number, bg-color1:number
+  color-quantum:number<span class="Special"> &lt;- </span>divide color-range:number, len:number
+<span class="CommentedCode">#?   close-console #? 2</span>
+<span class="CommentedCode">#?   $print len:number, [, ], color-range:number, [, ], color-quantum:number, [ </span>
+<span class="CommentedCode">#? ] #? 2</span>
+<span class="CommentedCode">#? #?   $exit #? 3</span>
+  bg-color:number<span class="Special"> &lt;- </span>copy bg-color1:number
+  i:number<span class="Special"> &lt;- </span>copy <span class="Constant">0:literal</span>
+  <span class="Delimiter">{</span>
+    done?:boolean<span class="Special"> &lt;- </span>greater-or-equal i:number, len:number
+    <span class="muControl">break-if</span> done?:boolean
+    c:character<span class="Special"> &lt;- </span>index s:address:array:character/deref, i:number
+    print-character x:address:screen, c:character, color:number, bg-color:number
+    i:number<span class="Special"> &lt;- </span>add i:number, <span class="Constant">1:literal</span>
+    bg-color:number<span class="Special"> &lt;- </span>add bg-color:number, color-quantum:number
+<span class="CommentedCode">#?     $print [=&gt; ], bg-color:number, [ </span>
+<span class="CommentedCode">#? ] #? 1</span>
+    <span class="muControl">loop</span>
+  <span class="Delimiter">}</span>
+<span class="CommentedCode">#?   $exit #? 1</span>
+  <span class="muControl">reply</span> x:address:screen/same-as-ingredient:0
+]
 </pre>
 </body>
 </html>