3789

I accidentally got rid of git snapshotting of lessons back when I switched to testable file primitives last December (commit 3705). >:-( Bringing it back now, hopefully better. The improvement is that there's now at most one commit every time we hit F4. This change adds yet another reason that running `mu` from a different directory is just not supported.
author: Kartik K. Agaram <vc@akkartik.com> 2017-03-12 00:31:55 -0800
committer: Kartik K. Agaram <vc@akkartik.com> 2017-03-12 00:34:02 -0800
commit: 2c53c3d0a921aec9825946be8dc37eff95b95485 (patch)
tree: 598e12608182300a97529082e317b36373ce6a36
parent: 465229a22a68f9c5cb94ba7853c44328f1bf85c1 (diff)
download: mu-2c53c3d0a921aec9825946be8dc37eff95b95485.tar.gz
10 files changed, 1062 insertions, 1046 deletions
diff --git a/edit/005-sandbox.mu b/edit/005-sandbox.mu
index f53ff96a..47ca5aec 100644
--- a/edit/005-sandbox.mu
+++ b/edit/005-sandbox.mu
@@ -144,7 +144,7 @@ def run-sandboxes env:&:environment, resources:&:resources, screen:&:screen -> e
   local-scope
   load-ingredients
   errors-found?:bool <- update-recipes env, resources, screen
-  return-if errors-found?
+  jump-if errors-found?, +return
   # check contents of right editor (sandbox)
   <run-sandboxes-begin>
   current-sandbox:&:editor <- get *env, current-sandbox:offset
@@ -181,6 +181,8 @@ def run-sandboxes env:&:environment, resources:&:resources, screen:&:screen -> e
     loop
   }
   <run-sandboxes-end>
+  +return
+  $system [./snapshot_lesson]
 ]
 
 # load code from disk
diff --git a/html/edit/005-sandbox.mu.html b/html/edit/005-sandbox.mu.html
index 8a7b3986..066a08a3 100644
--- a/html/edit/005-sandbox.mu.html
+++ b/html/edit/005-sandbox.mu.html
@@ -74,7 +74,7 @@ if ('onhashchange' in window) {
 <span id="L11" class="LineNr">  11 </span>  <span class="Constant">local-scope</span>
 <span id="L12" class="LineNr">  12 </span>  open-console
 <span id="L13" class="LineNr">  13 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <span class="Constant">0/filesystem</span>, <span class="Constant">0/screen</span>
-<span id="L14" class="LineNr">  14 </span>  env <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L417'>restore-sandboxes</a> env
+<span id="L14" class="LineNr">  14 </span>  env <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L419'>restore-sandboxes</a> env
 <span id="L15" class="LineNr">  15 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <span class="Constant">0/screen</span>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L16" class="LineNr">  16 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <span class="Constant">0/screen</span>, <span class="Constant">0/console</span>, env, <span class="Constant">0/filesystem</span>
 <span id="L17" class="LineNr">  17 </span>  <span class="Comment"># never gets here</span>
@@ -190,13 +190,13 @@ if ('onhashchange' in window) {
 <span id="L127" class="LineNr"> 127 </span>  <span class="Delimiter">{</span>
 <span id="L128" class="LineNr"> 128 </span>  <span class="Conceal">¦</span> do-run?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65532/F4</span>
 <span id="L129" class="LineNr"> 129 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> do-run?
-<span id="L130" class="LineNr"> 130 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[running...       ]</span>, <span class="Constant">245/grey</span>
+<span id="L130" class="LineNr"> 130 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L210'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[running...       ]</span>, <span class="Constant">245/grey</span>
 <span id="L131" class="LineNr"> 131 </span>  <span class="Conceal">¦</span> error?:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L143'>run-sandboxes</a> env, <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>
 <span id="L132" class="LineNr"> 132 </span>  <span class="Conceal">¦</span> <span class="Comment"># F4 might update warnings and results on both sides</span>
 <span id="L133" class="LineNr"> 133 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L134" class="LineNr"> 134 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
 <span id="L135" class="LineNr"> 135 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> error?
-<span id="L136" class="LineNr"> 136 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[                 ]</span>, <span class="Constant">245/grey</span>
+<span id="L136" class="LineNr"> 136 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L210'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[                 ]</span>, <span class="Constant">245/grey</span>
 <span id="L137" class="LineNr"> 137 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
 <span id="L138" class="LineNr"> 138 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L511'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
 <span id="L139" class="LineNr"> 139 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
@@ -207,12 +207,12 @@ if ('onhashchange' in window) {
 <span id="L144" class="LineNr"> 144 </span>  <span class="Constant">local-scope</span>
 <span id="L145" class="LineNr"> 145 </span>  <span class="Constant">load-ingredients</span>
 <span id="L146" class="LineNr"> 146 </span>  errors-found?:bool <span class="Special">&lt;-</span> update-recipes env, <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>
-<span id="L147" class="LineNr"> 147 </span>  <span class="muControl">return-if</span> errors-found?
+<span id="L147" class="LineNr"> 147 </span>  <span class="muControl">jump-if</span> errors-found?, <span class="Constant">+return</span>
 <span id="L148" class="LineNr"> 148 </span>  <span class="Comment"># check contents of right editor (sandbox)</span>
 <span id="L149" class="LineNr"> 149 </span><span class="Constant">  <a href='005-sandbox.mu.html#L149'>&lt;run-sandboxes-begin&gt;</a></span>
 <span id="L150" class="LineNr"> 150 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
 <span id="L151" class="LineNr"> 151 </span>  <span class="Delimiter">{</span>
-<span id="L152" class="LineNr"> 152 </span>  <span class="Conceal">¦</span> sandbox-contents:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L609'>editor-contents</a> current-sandbox
+<span id="L152" class="LineNr"> 152 </span>  <span class="Conceal">¦</span> sandbox-contents:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L611'>editor-contents</a> current-sandbox
 <span id="L153" class="LineNr"> 153 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-contents
 <span id="L154" class="LineNr"> 154 </span>  <span class="Conceal">¦</span> <span class="Comment"># if contents exist, first save them</span>
 <span id="L155" class="LineNr"> 155 </span>  <span class="Conceal">¦</span> <span class="Comment"># run them and turn them into a new sandbox</span>
@@ -232,7 +232,7 @@ if ('onhashchange' in window) {
 <span id="L169" class="LineNr"> 169 </span>  <span class="Conceal">¦</span> *current-sandbox <span class="Special">&lt;-</span> put *current-sandbox, <span class="Constant">top-of-screen:offset</span>, init
 <span id="L170" class="LineNr"> 170 </span>  <span class="Delimiter">}</span>
 <span id="L171" class="LineNr"> 171 </span>  <span class="Comment"># save all sandboxes before running, just in case we die when running</span>
-<span id="L172" class="LineNr"> 172 </span>  <a href='005-sandbox.mu.html#L215'>save-sandboxes</a> env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L172" class="LineNr"> 172 </span>  <a href='005-sandbox.mu.html#L217'>save-sandboxes</a> env, <a href='../088file.mu.html#L11'>resources</a>
 <span id="L173" class="LineNr"> 173 </span>  <span class="Comment"># run all sandboxes</span>
 <span id="L174" class="LineNr"> 174 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
 <span id="L175" class="LineNr"> 175 </span>  idx:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
@@ -244,1036 +244,1038 @@ if ('onhashchange' in window) {
 <span id="L181" class="LineNr"> 181 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
 <span id="L182" class="LineNr"> 182 </span>  <span class="Delimiter">}</span>
 <span id="L183" class="LineNr"> 183 </span><span class="Constant">  <a href='005-sandbox.mu.html#L183'>&lt;run-sandboxes-end&gt;</a></span>
-<span id="L184" class="LineNr"> 184 </span>]
-<span id="L185" class="LineNr"> 185 </span>
-<span id="L186" class="LineNr"> 186 </span><span class="Comment"># load code from disk</span>
-<span id="L187" class="LineNr"> 187 </span><span class="Comment"># replaced in a later layer (whereupon errors-found? will actually be set)</span>
-<span id="L188" class="LineNr"> 188 </span><span class="muRecipe">def</span> update-recipes env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a><span class="muRecipe"> -&gt; </span>errors-found?:bool, env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L189" class="LineNr"> 189 </span>  <span class="Constant">local-scope</span>
-<span id="L190" class="LineNr"> 190 </span>  <span class="Constant">load-ingredients</span>
-<span id="L191" class="LineNr"> 191 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L192" class="LineNr"> 192 </span>  in:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L609'>editor-contents</a> recipes
-<span id="L193" class="LineNr"> 193 </span>  <a href='../088file.mu.html#L11'>resources</a> <span class="Special">&lt;-</span> <a href='../088file.mu.html#L127'>dump</a> <a href='../088file.mu.html#L11'>resources</a>, <span class="Constant">[lesson/recipes.mu]</span>, in
-<span id="L194" class="LineNr"> 194 </span>  reload in
-<span id="L195" class="LineNr"> 195 </span>  errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
-<span id="L196" class="LineNr"> 196 </span>]
-<span id="L197" class="LineNr"> 197 </span>
-<span id="L198" class="LineNr"> 198 </span><span class="Comment"># replaced in a later layer</span>
-<span id="L199" class="LineNr"> 199 </span><span class="muRecipe">def</span> update-sandbox sandbox:&amp;:sandbox, env:&amp;:environment, idx:num<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox, env:&amp;:environment [
-<span id="L200" class="LineNr"> 200 </span>  <span class="Constant">local-scope</span>
-<span id="L201" class="LineNr"> 201 </span>  <span class="Constant">load-ingredients</span>
-<span id="L202" class="LineNr"> 202 </span>  data:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
-<span id="L203" class="LineNr"> 203 </span>  response:text, _, fake-screen:&amp;:<a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> run-sandboxed data
-<span id="L204" class="LineNr"> 204 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response:offset</span>, response
-<span id="L205" class="LineNr"> 205 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant"><a href='../081print.mu.html#L4'>screen</a>:offset</span>, fake-screen
-<span id="L206" class="LineNr"> 206 </span>]
-<span id="L207" class="LineNr"> 207 </span>
-<span id="L208" class="LineNr"> 208 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, msg:text, color:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L209" class="LineNr"> 209 </span>  <span class="Constant">local-scope</span>
-<span id="L210" class="LineNr"> 210 </span>  <span class="Constant">load-ingredients</span>
-<span id="L211" class="LineNr"> 211 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>,<span class="Constant"> 0</span>,<span class="Constant"> 2</span>
-<span id="L212" class="LineNr"> 212 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> print <a href='../081print.mu.html#L4'>screen</a>, msg, color, <span class="Constant">238/grey/background</span>
-<span id="L213" class="LineNr"> 213 </span>]
-<span id="L214" class="LineNr"> 214 </span>
-<span id="L215" class="LineNr"> 215 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L215'>save-sandboxes</a> env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a><span class="muRecipe"> -&gt; </span><a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a> [
-<span id="L216" class="LineNr"> 216 </span>  <span class="Constant">local-scope</span>
-<span id="L217" class="LineNr"> 217 </span>  <span class="Constant">load-ingredients</span>
-<span id="L218" class="LineNr"> 218 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L219" class="LineNr"> 219 </span>  <span class="Comment"># first clear previous versions, in case we deleted some sandbox</span>
-<span id="L220" class="LineNr"> 220 </span>  $system <span class="Constant">[rm lesson/[0-9]</span>* <span class="Constant">&gt;/dev/null</span> 2&gt;/dev/null]  <span class="Comment"># some shells can't handle '&gt;&amp;'</span>
-<span id="L221" class="LineNr"> 221 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L222" class="LineNr"> 222 </span>  idx:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
-<span id="L223" class="LineNr"> 223 </span>  <span class="Delimiter">{</span>
-<span id="L224" class="LineNr"> 224 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
-<span id="L225" class="LineNr"> 225 </span>  <span class="Conceal">¦</span> data:text <span class="Special">&lt;-</span> get *curr, <span class="Constant">data:offset</span>
-<span id="L226" class="LineNr"> 226 </span>  <span class="Conceal">¦</span> filename:text <span class="Special">&lt;-</span> append <span class="Constant">[lesson/]</span>, idx
-<span id="L227" class="LineNr"> 227 </span>  <span class="Conceal">¦</span> <a href='../088file.mu.html#L11'>resources</a> <span class="Special">&lt;-</span> <a href='../088file.mu.html#L127'>dump</a> <a href='../088file.mu.html#L11'>resources</a>, filename, data
-<span id="L228" class="LineNr"> 228 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L228'>&lt;end-save-sandbox&gt;</a></span>
-<span id="L229" class="LineNr"> 229 </span>  <span class="Conceal">¦</span> idx <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
-<span id="L230" class="LineNr"> 230 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
-<span id="L231" class="LineNr"> 231 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L232" class="LineNr"> 232 </span>  <span class="Delimiter">}</span>
-<span id="L233" class="LineNr"> 233 </span>]
-<span id="L234" class="LineNr"> 234 </span>
-<span id="L235" class="LineNr"> 235 </span><span class="muRecipe">def!</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
-<span id="L236" class="LineNr"> 236 </span>  <span class="Constant">local-scope</span>
-<span id="L237" class="LineNr"> 237 </span>  <span class="Constant">load-ingredients</span>
-<span id="L238" class="LineNr"> 238 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render sandbox side]</span>
-<span id="L239" class="LineNr"> 239 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
-<span id="L240" class="LineNr"> 240 </span>  row:num, column:num <span class="Special">&lt;-</span> copy<span class="Constant"> 1</span>,<span class="Constant"> 0</span>
-<span id="L241" class="LineNr"> 241 </span>  left:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
-<span id="L242" class="LineNr"> 242 </span>  right:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">right:offset</span>
-<span id="L243" class="LineNr"> 243 </span>  <span class="Comment"># render sandbox editor</span>
-<span id="L244" class="LineNr"> 244 </span>  render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
-<span id="L245" class="LineNr"> 245 </span>  <span class="Delimiter">{</span>
-<span id="L246" class="LineNr"> 246 </span>  <span class="Conceal">¦</span> render-current-sandbox?:bool <span class="Special">&lt;-</span> equal render-from,<span class="Constant"> -1</span>
-<span id="L247" class="LineNr"> 247 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> render-current-sandbox?
-<span id="L248" class="LineNr"> 248 </span>  <span class="Conceal">¦</span> row, column, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox <span class="Special">&lt;-</span> call render-editor, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox
-<span id="L249" class="LineNr"> 249 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L224'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, column, left, right
-<span id="L250" class="LineNr"> 250 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L251" class="LineNr"> 251 </span>  <span class="Delimiter">}</span>
-<span id="L252" class="LineNr"> 252 </span>  <span class="Comment"># render sandboxes</span>
-<span id="L253" class="LineNr"> 253 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
-<span id="L254" class="LineNr"> 254 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L255" class="LineNr"> 255 </span>  row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L259'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox, left, right, row, render-from
-<span id="L256" class="LineNr"> 256 </span>  <a href='001-editor.mu.html#L239'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
-<span id="L257" class="LineNr"> 257 </span>]
-<span id="L258" class="LineNr"> 258 </span>
-<span id="L259" class="LineNr"> 259 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L259'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox:&amp;:sandbox, left:num, right:num, row:num, render-from:num, idx:num<span class="muRecipe"> -&gt; </span>row:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox:&amp;:sandbox [
-<span id="L260" class="LineNr"> 260 </span>  <span class="Constant">local-scope</span>
-<span id="L261" class="LineNr"> 261 </span>  <span class="Constant">load-ingredients</span>
-<span id="L262" class="LineNr"> 262 </span>  <span class="muControl">return-unless</span> sandbox
-<span id="L263" class="LineNr"> 263 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L264" class="LineNr"> 264 </span>  at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
-<span id="L265" class="LineNr"> 265 </span>  <span class="muControl">return-if</span> at-bottom?:bool
-<span id="L266" class="LineNr"> 266 </span>  hidden?:bool <span class="Special">&lt;-</span> lesser-than idx, render-from
-<span id="L267" class="LineNr"> 267 </span>  <span class="Delimiter">{</span>
-<span id="L268" class="LineNr"> 268 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> hidden?
-<span id="L269" class="LineNr"> 269 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox menu</span>
-<span id="L270" class="LineNr"> 270 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L271" class="LineNr"> 271 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
-<span id="L272" class="LineNr"> 272 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L314'>render-sandbox-menu</a> <a href='../081print.mu.html#L4'>screen</a>, idx, left, right
-<span id="L273" class="LineNr"> 273 </span>  <span class="Conceal">¦</span> <span class="Comment"># save menu row so we can detect clicks to it later</span>
-<span id="L274" class="LineNr"> 274 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">starting-row-on-screen:offset</span>, row
-<span id="L275" class="LineNr"> 275 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox contents</span>
-<span id="L276" class="LineNr"> 276 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L277" class="LineNr"> 277 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
-<span id="L278" class="LineNr"> 278 </span>  <span class="Conceal">¦</span> sandbox-data:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
-<span id="L279" class="LineNr"> 279 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L529'>render-code</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-data, left, right, row
-<span id="L280" class="LineNr"> 280 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>, row
-<span id="L281" class="LineNr"> 281 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox warnings, screen or response, in that order</span>
-<span id="L282" class="LineNr"> 282 </span>  <span class="Conceal">¦</span> sandbox-response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">response:offset</span>
-<span id="L283" class="LineNr"> 283 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L283'>&lt;render-sandbox-results&gt;</a></span>
-<span id="L284" class="LineNr"> 284 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L285" class="LineNr"> 285 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> sandbox-screen:&amp;:<a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> get *sandbox, <span class="Constant"><a href='../081print.mu.html#L4'>screen</a>:offset</span>
-<span id="L286" class="LineNr"> 286 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> empty-screen?:bool <span class="Special">&lt;-</span> <a href='../081print.mu.html#L60'>fake-screen-is-empty?</a> sandbox-screen
-<span id="L287" class="LineNr"> 287 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> empty-screen?
-<span id="L288" class="LineNr"> 288 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L451'>render-screen</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-screen, left, right, row
-<span id="L289" class="LineNr"> 289 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L290" class="LineNr"> 290 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L291" class="LineNr"> 291 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> empty-screen?
-<span id="L292" class="LineNr"> 292 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L292'>&lt;render-sandbox-response&gt;</a></span>
-<span id="L293" class="LineNr"> 293 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">245/grey</span>, row
-<span id="L294" class="LineNr"> 294 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L295" class="LineNr"> 295 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +render-sandbox-end</span>
-<span id="L296" class="LineNr"> 296 </span>  <span class="Conceal">¦</span> at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
-<span id="L297" class="LineNr"> 297 </span>  <span class="Conceal">¦</span> <span class="muControl">return-if</span> at-bottom?
-<span id="L298" class="LineNr"> 298 </span>  <span class="Conceal">¦</span> <span class="Comment"># draw solid line after sandbox</span>
-<span id="L299" class="LineNr"> 299 </span>  <span class="Conceal">¦</span> <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
-<span id="L300" class="LineNr"> 300 </span>  <span class="Delimiter">}</span>
-<span id="L301" class="LineNr"> 301 </span>  <span class="Comment"># if hidden, reset row attributes</span>
-<span id="L302" class="LineNr"> 302 </span>  <span class="Delimiter">{</span>
-<span id="L303" class="LineNr"> 303 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> hidden?
-<span id="L304" class="LineNr"> 304 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">starting-row-on-screen:offset</span>,<span class="Constant"> 0</span>
-<span id="L305" class="LineNr"> 305 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>,<span class="Constant"> 0</span>
-<span id="L306" class="LineNr"> 306 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L306'>&lt;end-render-sandbox-reset-hidden&gt;</a></span>
-<span id="L307" class="LineNr"> 307 </span>  <span class="Delimiter">}</span>
-<span id="L308" class="LineNr"> 308 </span>  <span class="Comment"># draw next sandbox</span>
-<span id="L309" class="LineNr"> 309 </span>  next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">next-sandbox:offset</span>
-<span id="L310" class="LineNr"> 310 </span>  next-idx:num <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
-<span id="L311" class="LineNr"> 311 </span>  row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L259'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>, next-sandbox, left, right, row, render-from, next-idx
-<span id="L312" class="LineNr"> 312 </span>]
-<span id="L313" class="LineNr"> 313 </span>
-<span id="L314" class="LineNr"> 314 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L314'>render-sandbox-menu</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox-index:num, left:num, right:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L315" class="LineNr"> 315 </span>  <span class="Constant">local-scope</span>
-<span id="L316" class="LineNr"> 316 </span>  <span class="Constant">load-ingredients</span>
-<span id="L317" class="LineNr"> 317 </span>  <a href='../081print.mu.html#L574'>move-cursor-to-column</a> <a href='../081print.mu.html#L4'>screen</a>, left
-<span id="L318" class="LineNr"> 318 </span>  edit-button-left:num, edit-button-right:num, copy-button-left:num, copy-button-right:num, delete-button-left:num <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L339'>sandbox-menu-columns</a> left, right
-<span id="L319" class="LineNr"> 319 </span>  print <a href='../081print.mu.html#L4'>screen</a>, sandbox-index, <span class="Constant">232/dark-grey</span>, <span class="Constant">245/grey</span>
-<span id="L320" class="LineNr"> 320 </span>  start-buttons:num <span class="Special">&lt;-</span> subtract edit-button-left,<span class="Constant"> 1</span>
-<span id="L321" class="LineNr"> 321 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, start-buttons, <span class="Constant">245/grey</span>
-<span id="L322" class="LineNr"> 322 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[edit]</span>, <span class="Constant">232/black</span>, <span class="Constant">94/background-orange</span>
-<span id="L323" class="LineNr"> 323 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, edit-button-right, <span class="Constant">94/background-orange</span>
-<span id="L324" class="LineNr"> 324 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L428'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L325" class="LineNr"> 325 </span>  at-start-of-copy-button?:bool <span class="Special">&lt;-</span> equal col, copy-button-left
-<span id="L326" class="LineNr"> 326 </span>  assert at-start-of-copy-button?, <span class="Constant">[aaa]</span>
-<span id="L327" class="LineNr"> 327 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[copy]</span>, <span class="Constant">232/black</span>, <span class="Constant">58/background-green</span>
-<span id="L328" class="LineNr"> 328 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, copy-button-right, <span class="Constant">58/background-green</span>
-<span id="L329" class="LineNr"> 329 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L428'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L330" class="LineNr"> 330 </span>  at-start-of-delete-button?:bool <span class="Special">&lt;-</span> equal col, delete-button-left
-<span id="L331" class="LineNr"> 331 </span>  assert at-start-of-delete-button?, <span class="Constant">[bbb]</span>
-<span id="L332" class="LineNr"> 332 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[delete]</span>, <span class="Constant">232/black</span>, <span class="Constant">52/background-red</span>
-<span id="L333" class="LineNr"> 333 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right, <span class="Constant">52/background-red</span>
-<span id="L334" class="LineNr"> 334 </span>]
-<span id="L335" class="LineNr"> 335 </span>
-<span id="L336" class="LineNr"> 336 </span><span class="Comment"># divide up the menu bar for a sandbox into 3 segments, for edit/copy/delete buttons</span>
-<span id="L337" class="LineNr"> 337 </span><span class="Comment"># delete-button-right == right</span>
-<span id="L338" class="LineNr"> 338 </span><span class="Comment"># all left/right pairs are inclusive</span>
-<span id="L339" class="LineNr"> 339 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L339'>sandbox-menu-columns</a> left:num, right:num<span class="muRecipe"> -&gt; </span>edit-button-left:num, edit-button-right:num, copy-button-left:num, copy-button-right:num, delete-button-left:num [
-<span id="L340" class="LineNr"> 340 </span>  <span class="Constant">local-scope</span>
-<span id="L341" class="LineNr"> 341 </span>  <span class="Constant">load-ingredients</span>
-<span id="L342" class="LineNr"> 342 </span>  start-buttons:num <span class="Special">&lt;-</span> add left, <span class="Constant">4/space-for-sandbox-index</span>
-<span id="L343" class="LineNr"> 343 </span>  buttons-space:num <span class="Special">&lt;-</span> subtract right, start-buttons
-<span id="L344" class="LineNr"> 344 </span>  button-width:num <span class="Special">&lt;-</span> divide-with-remainder buttons-space,<span class="Constant"> 3</span>  <span class="Comment"># integer division</span>
-<span id="L345" class="LineNr"> 345 </span>  buttons-wide-enough?:bool <span class="Special">&lt;-</span> greater-or-equal button-width,<span class="Constant"> 8</span>
-<span id="L346" class="LineNr"> 346 </span>  assert buttons-wide-enough?, <span class="Constant">[sandbox must be at least 30 or so characters wide]</span>
-<span id="L347" class="LineNr"> 347 </span>  edit-button-left:num <span class="Special">&lt;-</span> copy start-buttons
-<span id="L348" class="LineNr"> 348 </span>  copy-button-left:num <span class="Special">&lt;-</span> add start-buttons, button-width
-<span id="L349" class="LineNr"> 349 </span>  edit-button-right:num <span class="Special">&lt;-</span> subtract copy-button-left,<span class="Constant"> 1</span>
-<span id="L350" class="LineNr"> 350 </span>  delete-button-left:num <span class="Special">&lt;-</span> subtract right, button-width
-<span id="L351" class="LineNr"> 351 </span>  copy-button-right:num <span class="Special">&lt;-</span> subtract delete-button-left,<span class="Constant"> 1</span>
-<span id="L352" class="LineNr"> 352 </span>]
-<span id="L353" class="LineNr"> 353 </span>
-<span id="L354" class="LineNr"> 354 </span><span class="Comment"># print a text 's' to 'editor' in 'color' starting at 'row'</span>
-<span id="L355" class="LineNr"> 355 </span><span class="Comment"># clear rest of last line, move cursor to next line</span>
-<span id="L356" class="LineNr"> 356 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, s:text, left:num, right:num, color:num, row:num<span class="muRecipe"> -&gt; </span>row:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L357" class="LineNr"> 357 </span>  <span class="Constant">local-scope</span>
-<span id="L358" class="LineNr"> 358 </span>  <span class="Constant">load-ingredients</span>
-<span id="L359" class="LineNr"> 359 </span>  <span class="muControl">return-unless</span> s
-<span id="L360" class="LineNr"> 360 </span>  column:num <span class="Special">&lt;-</span> copy left
-<span id="L361" class="LineNr"> 361 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L362" class="LineNr"> 362 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L363" class="LineNr"> 363 </span>  i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
-<span id="L364" class="LineNr"> 364 </span>  len:num <span class="Special">&lt;-</span> length *s
-<span id="L365" class="LineNr"> 365 </span>  <span class="Delimiter">{</span>
-<span id="L366" class="LineNr"> 366 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
-<span id="L367" class="LineNr"> 367 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal i, len
-<span id="L368" class="LineNr"> 368 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L369" class="LineNr"> 369 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L184" class="LineNr"> 184 </span><span class="Constant">  +return</span>
+<span id="L185" class="LineNr"> 185 </span>  $system <span class="Constant">[./snapshot_lesson]</span>
+<span id="L186" class="LineNr"> 186 </span>]
+<span id="L187" class="LineNr"> 187 </span>
+<span id="L188" class="LineNr"> 188 </span><span class="Comment"># load code from disk</span>
+<span id="L189" class="LineNr"> 189 </span><span class="Comment"># replaced in a later layer (whereupon errors-found? will actually be set)</span>
+<span id="L190" class="LineNr"> 190 </span><span class="muRecipe">def</span> update-recipes env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a><span class="muRecipe"> -&gt; </span>errors-found?:bool, env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L191" class="LineNr"> 191 </span>  <span class="Constant">local-scope</span>
+<span id="L192" class="LineNr"> 192 </span>  <span class="Constant">load-ingredients</span>
+<span id="L193" class="LineNr"> 193 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
+<span id="L194" class="LineNr"> 194 </span>  in:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L611'>editor-contents</a> recipes
+<span id="L195" class="LineNr"> 195 </span>  <a href='../088file.mu.html#L11'>resources</a> <span class="Special">&lt;-</span> <a href='../088file.mu.html#L127'>dump</a> <a href='../088file.mu.html#L11'>resources</a>, <span class="Constant">[lesson/recipes.mu]</span>, in
+<span id="L196" class="LineNr"> 196 </span>  reload in
+<span id="L197" class="LineNr"> 197 </span>  errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">0/false</span>
+<span id="L198" class="LineNr"> 198 </span>]
+<span id="L199" class="LineNr"> 199 </span>
+<span id="L200" class="LineNr"> 200 </span><span class="Comment"># replaced in a later layer</span>
+<span id="L201" class="LineNr"> 201 </span><span class="muRecipe">def</span> update-sandbox sandbox:&amp;:sandbox, env:&amp;:environment, idx:num<span class="muRecipe"> -&gt; </span>sandbox:&amp;:sandbox, env:&amp;:environment [
+<span id="L202" class="LineNr"> 202 </span>  <span class="Constant">local-scope</span>
+<span id="L203" class="LineNr"> 203 </span>  <span class="Constant">load-ingredients</span>
+<span id="L204" class="LineNr"> 204 </span>  data:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
+<span id="L205" class="LineNr"> 205 </span>  response:text, _, fake-screen:&amp;:<a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> run-sandboxed data
+<span id="L206" class="LineNr"> 206 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response:offset</span>, response
+<span id="L207" class="LineNr"> 207 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant"><a href='../081print.mu.html#L4'>screen</a>:offset</span>, fake-screen
+<span id="L208" class="LineNr"> 208 </span>]
+<span id="L209" class="LineNr"> 209 </span>
+<span id="L210" class="LineNr"> 210 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L210'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, msg:text, color:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L211" class="LineNr"> 211 </span>  <span class="Constant">local-scope</span>
+<span id="L212" class="LineNr"> 212 </span>  <span class="Constant">load-ingredients</span>
+<span id="L213" class="LineNr"> 213 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>,<span class="Constant"> 0</span>,<span class="Constant"> 2</span>
+<span id="L214" class="LineNr"> 214 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> print <a href='../081print.mu.html#L4'>screen</a>, msg, color, <span class="Constant">238/grey/background</span>
+<span id="L215" class="LineNr"> 215 </span>]
+<span id="L216" class="LineNr"> 216 </span>
+<span id="L217" class="LineNr"> 217 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L217'>save-sandboxes</a> env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a><span class="muRecipe"> -&gt; </span><a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a> [
+<span id="L218" class="LineNr"> 218 </span>  <span class="Constant">local-scope</span>
+<span id="L219" class="LineNr"> 219 </span>  <span class="Constant">load-ingredients</span>
+<span id="L220" class="LineNr"> 220 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L221" class="LineNr"> 221 </span>  <span class="Comment"># first clear previous versions, in case we deleted some sandbox</span>
+<span id="L222" class="LineNr"> 222 </span>  $system <span class="Constant">[rm lesson/[0-9]</span>* <span class="Constant">&gt;/dev/null</span> 2&gt;/dev/null]  <span class="Comment"># some shells can't handle '&gt;&amp;'</span>
+<span id="L223" class="LineNr"> 223 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L224" class="LineNr"> 224 </span>  idx:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L225" class="LineNr"> 225 </span>  <span class="Delimiter">{</span>
+<span id="L226" class="LineNr"> 226 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
+<span id="L227" class="LineNr"> 227 </span>  <span class="Conceal">¦</span> data:text <span class="Special">&lt;-</span> get *curr, <span class="Constant">data:offset</span>
+<span id="L228" class="LineNr"> 228 </span>  <span class="Conceal">¦</span> filename:text <span class="Special">&lt;-</span> append <span class="Constant">[lesson/]</span>, idx
+<span id="L229" class="LineNr"> 229 </span>  <span class="Conceal">¦</span> <a href='../088file.mu.html#L11'>resources</a> <span class="Special">&lt;-</span> <a href='../088file.mu.html#L127'>dump</a> <a href='../088file.mu.html#L11'>resources</a>, filename, data
+<span id="L230" class="LineNr"> 230 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L230'>&lt;end-save-sandbox&gt;</a></span>
+<span id="L231" class="LineNr"> 231 </span>  <span class="Conceal">¦</span> idx <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
+<span id="L232" class="LineNr"> 232 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
+<span id="L233" class="LineNr"> 233 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L234" class="LineNr"> 234 </span>  <span class="Delimiter">}</span>
+<span id="L235" class="LineNr"> 235 </span>]
+<span id="L236" class="LineNr"> 236 </span>
+<span id="L237" class="LineNr"> 237 </span><span class="muRecipe">def!</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment, <span class="Delimiter">{</span>render-editor: (recipe (address screen) (address editor)<span class="muRecipe"> -&gt; </span>number number (address screen) (address editor))<span class="Delimiter">}</span><span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, env:&amp;:environment [
+<span id="L238" class="LineNr"> 238 </span>  <span class="Constant">local-scope</span>
+<span id="L239" class="LineNr"> 239 </span>  <span class="Constant">load-ingredients</span>
+<span id="L240" class="LineNr"> 240 </span>  trace<span class="Constant"> 11</span>, <span class="Constant">[app]</span>, <span class="Constant">[render sandbox side]</span>
+<span id="L241" class="LineNr"> 241 </span>  current-sandbox:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">current-sandbox:offset</span>
+<span id="L242" class="LineNr"> 242 </span>  row:num, column:num <span class="Special">&lt;-</span> copy<span class="Constant"> 1</span>,<span class="Constant"> 0</span>
+<span id="L243" class="LineNr"> 243 </span>  left:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
+<span id="L244" class="LineNr"> 244 </span>  right:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">right:offset</span>
+<span id="L245" class="LineNr"> 245 </span>  <span class="Comment"># render sandbox editor</span>
+<span id="L246" class="LineNr"> 246 </span>  render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
+<span id="L247" class="LineNr"> 247 </span>  <span class="Delimiter">{</span>
+<span id="L248" class="LineNr"> 248 </span>  <span class="Conceal">¦</span> render-current-sandbox?:bool <span class="Special">&lt;-</span> equal render-from,<span class="Constant"> -1</span>
+<span id="L249" class="LineNr"> 249 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> render-current-sandbox?
+<span id="L250" class="LineNr"> 250 </span>  <span class="Conceal">¦</span> row, column, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox <span class="Special">&lt;-</span> call render-editor, <a href='../081print.mu.html#L4'>screen</a>, current-sandbox
+<span id="L251" class="LineNr"> 251 </span>  <span class="Conceal">¦</span> <a href='001-editor.mu.html#L224'>clear-screen-from</a> <a href='../081print.mu.html#L4'>screen</a>, row, column, left, right
+<span id="L252" class="LineNr"> 252 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L253" class="LineNr"> 253 </span>  <span class="Delimiter">}</span>
+<span id="L254" class="LineNr"> 254 </span>  <span class="Comment"># render sandboxes</span>
+<span id="L255" class="LineNr"> 255 </span>  <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
+<span id="L256" class="LineNr"> 256 </span>  sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L257" class="LineNr"> 257 </span>  row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L261'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox, left, right, row, render-from
+<span id="L258" class="LineNr"> 258 </span>  <a href='001-editor.mu.html#L239'>clear-rest-of-screen</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
+<span id="L259" class="LineNr"> 259 </span>]
+<span id="L260" class="LineNr"> 260 </span>
+<span id="L261" class="LineNr"> 261 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L261'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox:&amp;:sandbox, left:num, right:num, row:num, render-from:num, idx:num<span class="muRecipe"> -&gt; </span>row:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox:&amp;:sandbox [
+<span id="L262" class="LineNr"> 262 </span>  <span class="Constant">local-scope</span>
+<span id="L263" class="LineNr"> 263 </span>  <span class="Constant">load-ingredients</span>
+<span id="L264" class="LineNr"> 264 </span>  <span class="muControl">return-unless</span> sandbox
+<span id="L265" class="LineNr"> 265 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L266" class="LineNr"> 266 </span>  at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L267" class="LineNr"> 267 </span>  <span class="muControl">return-if</span> at-bottom?:bool
+<span id="L268" class="LineNr"> 268 </span>  hidden?:bool <span class="Special">&lt;-</span> lesser-than idx, render-from
+<span id="L269" class="LineNr"> 269 </span>  <span class="Delimiter">{</span>
+<span id="L270" class="LineNr"> 270 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> hidden?
+<span id="L271" class="LineNr"> 271 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox menu</span>
+<span id="L272" class="LineNr"> 272 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L273" class="LineNr"> 273 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L274" class="LineNr"> 274 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L316'>render-sandbox-menu</a> <a href='../081print.mu.html#L4'>screen</a>, idx, left, right
+<span id="L275" class="LineNr"> 275 </span>  <span class="Conceal">¦</span> <span class="Comment"># save menu row so we can detect clicks to it later</span>
+<span id="L276" class="LineNr"> 276 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">starting-row-on-screen:offset</span>, row
+<span id="L277" class="LineNr"> 277 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox contents</span>
+<span id="L278" class="LineNr"> 278 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L279" class="LineNr"> 279 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L280" class="LineNr"> 280 </span>  <span class="Conceal">¦</span> sandbox-data:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">data:offset</span>
+<span id="L281" class="LineNr"> 281 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L529'>render-code</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-data, left, right, row
+<span id="L282" class="LineNr"> 282 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>, row
+<span id="L283" class="LineNr"> 283 </span>  <span class="Conceal">¦</span> <span class="Comment"># render sandbox warnings, screen or response, in that order</span>
+<span id="L284" class="LineNr"> 284 </span>  <span class="Conceal">¦</span> sandbox-response:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">response:offset</span>
+<span id="L285" class="LineNr"> 285 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L285'>&lt;render-sandbox-results&gt;</a></span>
+<span id="L286" class="LineNr"> 286 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L287" class="LineNr"> 287 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> sandbox-screen:&amp;:<a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> get *sandbox, <span class="Constant"><a href='../081print.mu.html#L4'>screen</a>:offset</span>
+<span id="L288" class="LineNr"> 288 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> empty-screen?:bool <span class="Special">&lt;-</span> <a href='../081print.mu.html#L60'>fake-screen-is-empty?</a> sandbox-screen
+<span id="L289" class="LineNr"> 289 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> empty-screen?
+<span id="L290" class="LineNr"> 290 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L453'>render-screen</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-screen, left, right, row
+<span id="L291" class="LineNr"> 291 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L292" class="LineNr"> 292 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L293" class="LineNr"> 293 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> empty-screen?
+<span id="L294" class="LineNr"> 294 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L294'>&lt;render-sandbox-response&gt;</a></span>
+<span id="L295" class="LineNr"> 295 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">245/grey</span>, row
+<span id="L296" class="LineNr"> 296 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L297" class="LineNr"> 297 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +render-sandbox-end</span>
+<span id="L298" class="LineNr"> 298 </span>  <span class="Conceal">¦</span> at-bottom?:bool <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L299" class="LineNr"> 299 </span>  <span class="Conceal">¦</span> <span class="muControl">return-if</span> at-bottom?
+<span id="L300" class="LineNr"> 300 </span>  <span class="Conceal">¦</span> <span class="Comment"># draw solid line after sandbox</span>
+<span id="L301" class="LineNr"> 301 </span>  <span class="Conceal">¦</span> <a href='002-typing.mu.html#L1056'>draw-horizontal</a> <a href='../081print.mu.html#L4'>screen</a>, row, left, right
+<span id="L302" class="LineNr"> 302 </span>  <span class="Delimiter">}</span>
+<span id="L303" class="LineNr"> 303 </span>  <span class="Comment"># if hidden, reset row attributes</span>
+<span id="L304" class="LineNr"> 304 </span>  <span class="Delimiter">{</span>
+<span id="L305" class="LineNr"> 305 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> hidden?
+<span id="L306" class="LineNr"> 306 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">starting-row-on-screen:offset</span>,<span class="Constant"> 0</span>
+<span id="L307" class="LineNr"> 307 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">code-ending-row-on-screen:offset</span>,<span class="Constant"> 0</span>
+<span id="L308" class="LineNr"> 308 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L308'>&lt;end-render-sandbox-reset-hidden&gt;</a></span>
+<span id="L309" class="LineNr"> 309 </span>  <span class="Delimiter">}</span>
+<span id="L310" class="LineNr"> 310 </span>  <span class="Comment"># draw next sandbox</span>
+<span id="L311" class="LineNr"> 311 </span>  next-sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">next-sandbox:offset</span>
+<span id="L312" class="LineNr"> 312 </span>  next-idx:num <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
+<span id="L313" class="LineNr"> 313 </span>  row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L261'>render-sandboxes</a> <a href='../081print.mu.html#L4'>screen</a>, next-sandbox, left, right, row, render-from, next-idx
+<span id="L314" class="LineNr"> 314 </span>]
+<span id="L315" class="LineNr"> 315 </span>
+<span id="L316" class="LineNr"> 316 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L316'>render-sandbox-menu</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox-index:num, left:num, right:num<span class="muRecipe"> -&gt; </span><a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L317" class="LineNr"> 317 </span>  <span class="Constant">local-scope</span>
+<span id="L318" class="LineNr"> 318 </span>  <span class="Constant">load-ingredients</span>
+<span id="L319" class="LineNr"> 319 </span>  <a href='../081print.mu.html#L574'>move-cursor-to-column</a> <a href='../081print.mu.html#L4'>screen</a>, left
+<span id="L320" class="LineNr"> 320 </span>  edit-button-left:num, edit-button-right:num, copy-button-left:num, copy-button-right:num, delete-button-left:num <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L341'>sandbox-menu-columns</a> left, right
+<span id="L321" class="LineNr"> 321 </span>  print <a href='../081print.mu.html#L4'>screen</a>, sandbox-index, <span class="Constant">232/dark-grey</span>, <span class="Constant">245/grey</span>
+<span id="L322" class="LineNr"> 322 </span>  start-buttons:num <span class="Special">&lt;-</span> subtract edit-button-left,<span class="Constant"> 1</span>
+<span id="L323" class="LineNr"> 323 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, start-buttons, <span class="Constant">245/grey</span>
+<span id="L324" class="LineNr"> 324 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[edit]</span>, <span class="Constant">232/black</span>, <span class="Constant">94/background-orange</span>
+<span id="L325" class="LineNr"> 325 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, edit-button-right, <span class="Constant">94/background-orange</span>
+<span id="L326" class="LineNr"> 326 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L428'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L327" class="LineNr"> 327 </span>  at-start-of-copy-button?:bool <span class="Special">&lt;-</span> equal col, copy-button-left
+<span id="L328" class="LineNr"> 328 </span>  assert at-start-of-copy-button?, <span class="Constant">[aaa]</span>
+<span id="L329" class="LineNr"> 329 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[copy]</span>, <span class="Constant">232/black</span>, <span class="Constant">58/background-green</span>
+<span id="L330" class="LineNr"> 330 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, copy-button-right, <span class="Constant">58/background-green</span>
+<span id="L331" class="LineNr"> 331 </span>  _, col:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L428'>cursor-position</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L332" class="LineNr"> 332 </span>  at-start-of-delete-button?:bool <span class="Special">&lt;-</span> equal col, delete-button-left
+<span id="L333" class="LineNr"> 333 </span>  assert at-start-of-delete-button?, <span class="Constant">[bbb]</span>
+<span id="L334" class="LineNr"> 334 </span>  print <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[delete]</span>, <span class="Constant">232/black</span>, <span class="Constant">52/background-red</span>
+<span id="L335" class="LineNr"> 335 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right, <span class="Constant">52/background-red</span>
+<span id="L336" class="LineNr"> 336 </span>]
+<span id="L337" class="LineNr"> 337 </span>
+<span id="L338" class="LineNr"> 338 </span><span class="Comment"># divide up the menu bar for a sandbox into 3 segments, for edit/copy/delete buttons</span>
+<span id="L339" class="LineNr"> 339 </span><span class="Comment"># delete-button-right == right</span>
+<span id="L340" class="LineNr"> 340 </span><span class="Comment"># all left/right pairs are inclusive</span>
+<span id="L341" class="LineNr"> 341 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L341'>sandbox-menu-columns</a> left:num, right:num<span class="muRecipe"> -&gt; </span>edit-button-left:num, edit-button-right:num, copy-button-left:num, copy-button-right:num, delete-button-left:num [
+<span id="L342" class="LineNr"> 342 </span>  <span class="Constant">local-scope</span>
+<span id="L343" class="LineNr"> 343 </span>  <span class="Constant">load-ingredients</span>
+<span id="L344" class="LineNr"> 344 </span>  start-buttons:num <span class="Special">&lt;-</span> add left, <span class="Constant">4/space-for-sandbox-index</span>
+<span id="L345" class="LineNr"> 345 </span>  buttons-space:num <span class="Special">&lt;-</span> subtract right, start-buttons
+<span id="L346" class="LineNr"> 346 </span>  button-width:num <span class="Special">&lt;-</span> divide-with-remainder buttons-space,<span class="Constant"> 3</span>  <span class="Comment"># integer division</span>
+<span id="L347" class="LineNr"> 347 </span>  buttons-wide-enough?:bool <span class="Special">&lt;-</span> greater-or-equal button-width,<span class="Constant"> 8</span>
+<span id="L348" class="LineNr"> 348 </span>  assert buttons-wide-enough?, <span class="Constant">[sandbox must be at least 30 or so characters wide]</span>
+<span id="L349" class="LineNr"> 349 </span>  edit-button-left:num <span class="Special">&lt;-</span> copy start-buttons
+<span id="L350" class="LineNr"> 350 </span>  copy-button-left:num <span class="Special">&lt;-</span> add start-buttons, button-width
+<span id="L351" class="LineNr"> 351 </span>  edit-button-right:num <span class="Special">&lt;-</span> subtract copy-button-left,<span class="Constant"> 1</span>
+<span id="L352" class="LineNr"> 352 </span>  delete-button-left:num <span class="Special">&lt;-</span> subtract right, button-width
+<span id="L353" class="LineNr"> 353 </span>  copy-button-right:num <span class="Special">&lt;-</span> subtract delete-button-left,<span class="Constant"> 1</span>
+<span id="L354" class="LineNr"> 354 </span>]
+<span id="L355" class="LineNr"> 355 </span>
+<span id="L356" class="LineNr"> 356 </span><span class="Comment"># print a text 's' to 'editor' in 'color' starting at 'row'</span>
+<span id="L357" class="LineNr"> 357 </span><span class="Comment"># clear rest of last line, move cursor to next line</span>
+<span id="L358" class="LineNr"> 358 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, s:text, left:num, right:num, color:num, row:num<span class="muRecipe"> -&gt; </span>row:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L359" class="LineNr"> 359 </span>  <span class="Constant">local-scope</span>
+<span id="L360" class="LineNr"> 360 </span>  <span class="Constant">load-ingredients</span>
+<span id="L361" class="LineNr"> 361 </span>  <span class="muControl">return-unless</span> s
+<span id="L362" class="LineNr"> 362 </span>  column:num <span class="Special">&lt;-</span> copy left
+<span id="L363" class="LineNr"> 363 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L364" class="LineNr"> 364 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L365" class="LineNr"> 365 </span>  i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L366" class="LineNr"> 366 </span>  len:num <span class="Special">&lt;-</span> length *s
+<span id="L367" class="LineNr"> 367 </span>  <span class="Delimiter">{</span>
+<span id="L368" class="LineNr"> 368 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> +next-character</span>
+<span id="L369" class="LineNr"> 369 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal i, len
 <span id="L370" class="LineNr"> 370 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L371" class="LineNr"> 371 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> index *s, i
-<span id="L372" class="LineNr"> 372 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L373" class="LineNr"> 373 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># at right? wrap.</span>
-<span id="L374" class="LineNr"> 374 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> equal column, right
-<span id="L375" class="LineNr"> 375 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-right?
-<span id="L376" class="LineNr"> 376 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print wrap icon</span>
-<span id="L377" class="LineNr"> 377 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> wrap-icon:char <span class="Special">&lt;-</span> copy <span class="Constant">8617/loop-back-to-left</span>
-<span id="L378" class="LineNr"> 378 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
-<span id="L379" class="LineNr"> 379 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L380" class="LineNr"> 380 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L381" class="LineNr"> 381 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L382" class="LineNr"> 382 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>  <span class="Comment"># retry i</span>
-<span id="L383" class="LineNr"> 383 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L384" class="LineNr"> 384 </span>  <span class="Conceal">¦</span> i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
-<span id="L385" class="LineNr"> 385 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L386" class="LineNr"> 386 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># newline? move to left rather than 0</span>
-<span id="L387" class="LineNr"> 387 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
-<span id="L388" class="LineNr"> 388 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> newline?
-<span id="L389" class="LineNr"> 389 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of line in this window</span>
-<span id="L390" class="LineNr"> 390 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L391" class="LineNr"> 391 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-than column, right
-<span id="L392" class="LineNr"> 392 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L393" class="LineNr"> 393 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> space:char <span class="Special">&lt;-</span> copy <span class="Constant">32/space</span>
-<span id="L394" class="LineNr"> 394 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space
-<span id="L395" class="LineNr"> 395 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
-<span id="L396" class="LineNr"> 396 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L397" class="LineNr"> 397 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L398" class="LineNr"> 398 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L399" class="LineNr"> 399 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L400" class="LineNr"> 400 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L401" class="LineNr"> 401 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
-<span id="L402" class="LineNr"> 402 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L403" class="LineNr"> 403 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
-<span id="L404" class="LineNr"> 404 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
-<span id="L405" class="LineNr"> 405 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L406" class="LineNr"> 406 </span>  <span class="Delimiter">}</span>
-<span id="L407" class="LineNr"> 407 </span>  was-at-left?:bool <span class="Special">&lt;-</span> equal column, left
-<span id="L408" class="LineNr"> 408 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
-<span id="L409" class="LineNr"> 409 </span>  <span class="Delimiter">{</span>
-<span id="L410" class="LineNr"> 410 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> was-at-left?
-<span id="L411" class="LineNr"> 411 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L412" class="LineNr"> 412 </span>  <span class="Delimiter">}</span>
-<span id="L413" class="LineNr"> 413 </span>  <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
-<span id="L414" class="LineNr"> 414 </span>]
-<span id="L415" class="LineNr"> 415 </span>
-<span id="L416" class="LineNr"> 416 </span><span class="Comment"># assumes programming environment has no sandboxes; restores them from previous session</span>
-<span id="L417" class="LineNr"> 417 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L417'>restore-sandboxes</a> env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a><span class="muRecipe"> -&gt; </span>env:&amp;:environment [
-<span id="L418" class="LineNr"> 418 </span>  <span class="Constant">local-scope</span>
-<span id="L419" class="LineNr"> 419 </span>  <span class="Constant">load-ingredients</span>
-<span id="L420" class="LineNr"> 420 </span>  <span class="Comment"># read all scenarios, pushing them to end of a list of scenarios</span>
-<span id="L421" class="LineNr"> 421 </span>  idx:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
-<span id="L422" class="LineNr"> 422 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
-<span id="L423" class="LineNr"> 423 </span>  <a href='../065duplex_list.mu.html#L36'>prev</a>:&amp;:sandbox <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
-<span id="L424" class="LineNr"> 424 </span>  <span class="Delimiter">{</span>
-<span id="L425" class="LineNr"> 425 </span>  <span class="Conceal">¦</span> filename:text <span class="Special">&lt;-</span> append <span class="Constant">[lesson/]</span>, idx
-<span id="L426" class="LineNr"> 426 </span>  <span class="Conceal">¦</span> contents:text <span class="Special">&lt;-</span> <a href='../088file.mu.html#L38'>slurp</a> <a href='../088file.mu.html#L11'>resources</a>, filename
-<span id="L427" class="LineNr"> 427 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> contents  <span class="Comment"># stop at first error; assuming file didn't exist</span>
-<span id="L428" class="LineNr"> 428 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span>      <span class="Comment"># todo: handle empty sandbox</span>
-<span id="L429" class="LineNr"> 429 </span>  <span class="Conceal">¦</span> <span class="Comment"># create new sandbox for file</span>
-<span id="L430" class="LineNr"> 430 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> new <span class="Constant">sandbox:type</span>
-<span id="L431" class="LineNr"> 431 </span>  <span class="Conceal">¦</span> *curr <span class="Special">&lt;-</span> put *curr, <span class="Constant">data:offset</span>, contents
-<span id="L432" class="LineNr"> 432 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L432'>&lt;end-restore-sandbox&gt;</a></span>
-<span id="L433" class="LineNr"> 433 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L434" class="LineNr"> 434 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> idx
-<span id="L435" class="LineNr"> 435 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox:offset</span>, curr
-<span id="L436" class="LineNr"> 436 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L437" class="LineNr"> 437 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L438" class="LineNr"> 438 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> idx
-<span id="L439" class="LineNr"> 439 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *prev <span class="Special">&lt;-</span> put *prev, <span class="Constant">next-sandbox:offset</span>, curr
-<span id="L440" class="LineNr"> 440 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L441" class="LineNr"> 441 </span>  <span class="Conceal">¦</span> idx <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
-<span id="L442" class="LineNr"> 442 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> copy curr
-<span id="L443" class="LineNr"> 443 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L444" class="LineNr"> 444 </span>  <span class="Delimiter">}</span>
-<span id="L445" class="LineNr"> 445 </span>  <span class="Comment"># update sandbox count</span>
-<span id="L446" class="LineNr"> 446 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">number-of-sandboxes:offset</span>, idx
-<span id="L447" class="LineNr"> 447 </span>]
-<span id="L448" class="LineNr"> 448 </span>
-<span id="L449" class="LineNr"> 449 </span><span class="Comment"># print the fake sandbox screen to 'screen' with appropriate delimiters</span>
-<span id="L450" class="LineNr"> 450 </span><span class="Comment"># leave cursor at start of next line</span>
-<span id="L451" class="LineNr"> 451 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L451'>render-screen</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox-screen:&amp;:<a href='../081print.mu.html#L4'>screen</a>, left:num, right:num, row:num<span class="muRecipe"> -&gt; </span>row:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
-<span id="L452" class="LineNr"> 452 </span>  <span class="Constant">local-scope</span>
-<span id="L453" class="LineNr"> 453 </span>  <span class="Constant">load-ingredients</span>
-<span id="L454" class="LineNr"> 454 </span>  <span class="muControl">return-unless</span> sandbox-screen
-<span id="L455" class="LineNr"> 455 </span>  <span class="Comment"># print 'screen:'</span>
-<span id="L456" class="LineNr"> 456 </span>  row <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[screen:]</span>, left, right, <span class="Constant">245/grey</span>, row
-<span id="L457" class="LineNr"> 457 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
-<span id="L458" class="LineNr"> 458 </span>  <span class="Comment"># start printing sandbox-screen</span>
-<span id="L459" class="LineNr"> 459 </span>  column:num <span class="Special">&lt;-</span> copy left
-<span id="L460" class="LineNr"> 460 </span>  s-width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> sandbox-screen
-<span id="L461" class="LineNr"> 461 </span>  s-height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> sandbox-screen
-<span id="L462" class="LineNr"> 462 </span>  buf:&amp;:@:<a href='../081print.mu.html#L12'>screen-cell</a> <span class="Special">&lt;-</span> get *sandbox-screen, <span class="Constant">data:offset</span>
-<span id="L463" class="LineNr"> 463 </span>  stop-printing:num <span class="Special">&lt;-</span> add left, s-width,<span class="Constant"> 3</span>
-<span id="L464" class="LineNr"> 464 </span>  max-column:num <span class="Special">&lt;-</span> min stop-printing, right
-<span id="L465" class="LineNr"> 465 </span>  i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
-<span id="L466" class="LineNr"> 466 </span>  len:num <span class="Special">&lt;-</span> length *buf
-<span id="L467" class="LineNr"> 467 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L468" class="LineNr"> 468 </span>  <span class="Delimiter">{</span>
-<span id="L469" class="LineNr"> 469 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal i, len
-<span id="L470" class="LineNr"> 470 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L471" class="LineNr"> 471 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L371" class="LineNr"> 371 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L372" class="LineNr"> 372 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
+<span id="L373" class="LineNr"> 373 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> index *s, i
+<span id="L374" class="LineNr"> 374 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L375" class="LineNr"> 375 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># at right? wrap.</span>
+<span id="L376" class="LineNr"> 376 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-right?:bool <span class="Special">&lt;-</span> equal column, right
+<span id="L377" class="LineNr"> 377 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-right?
+<span id="L378" class="LineNr"> 378 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print wrap icon</span>
+<span id="L379" class="LineNr"> 379 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> wrap-icon:char <span class="Special">&lt;-</span> copy <span class="Constant">8617/loop-back-to-left</span>
+<span id="L380" class="LineNr"> 380 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, wrap-icon, <span class="Constant">245/grey</span>
+<span id="L381" class="LineNr"> 381 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
+<span id="L382" class="LineNr"> 382 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L383" class="LineNr"> 383 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L384" class="LineNr"> 384 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>  <span class="Comment"># retry i</span>
+<span id="L385" class="LineNr"> 385 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L386" class="LineNr"> 386 </span>  <span class="Conceal">¦</span> i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
+<span id="L387" class="LineNr"> 387 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L388" class="LineNr"> 388 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># newline? move to left rather than 0</span>
+<span id="L389" class="LineNr"> 389 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> newline?:bool <span class="Special">&lt;-</span> equal c, <span class="Constant">10/newline</span>
+<span id="L390" class="LineNr"> 390 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> newline?
+<span id="L391" class="LineNr"> 391 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of line in this window</span>
+<span id="L392" class="LineNr"> 392 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L393" class="LineNr"> 393 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-than column, right
+<span id="L394" class="LineNr"> 394 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
+<span id="L395" class="LineNr"> 395 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> space:char <span class="Special">&lt;-</span> copy <span class="Constant">32/space</span>
+<span id="L396" class="LineNr"> 396 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space
+<span id="L397" class="LineNr"> 397 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
+<span id="L398" class="LineNr"> 398 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L399" class="LineNr"> 399 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L400" class="LineNr"> 400 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L401" class="LineNr"> 401 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
+<span id="L402" class="LineNr"> 402 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L403" class="LineNr"> 403 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-character</span>
+<span id="L404" class="LineNr"> 404 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L405" class="LineNr"> 405 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
+<span id="L406" class="LineNr"> 406 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
+<span id="L407" class="LineNr"> 407 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L408" class="LineNr"> 408 </span>  <span class="Delimiter">}</span>
+<span id="L409" class="LineNr"> 409 </span>  was-at-left?:bool <span class="Special">&lt;-</span> equal column, left
+<span id="L410" class="LineNr"> 410 </span>  <a href='../081print.mu.html#L408'>clear-line-until</a> <a href='../081print.mu.html#L4'>screen</a>, right
+<span id="L411" class="LineNr"> 411 </span>  <span class="Delimiter">{</span>
+<span id="L412" class="LineNr"> 412 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> was-at-left?
+<span id="L413" class="LineNr"> 413 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L414" class="LineNr"> 414 </span>  <span class="Delimiter">}</span>
+<span id="L415" class="LineNr"> 415 </span>  <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L416" class="LineNr"> 416 </span>]
+<span id="L417" class="LineNr"> 417 </span>
+<span id="L418" class="LineNr"> 418 </span><span class="Comment"># assumes programming environment has no sandboxes; restores them from previous session</span>
+<span id="L419" class="LineNr"> 419 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L419'>restore-sandboxes</a> env:&amp;:environment, <a href='../088file.mu.html#L11'>resources</a>:&amp;:<a href='../088file.mu.html#L11'>resources</a><span class="muRecipe"> -&gt; </span>env:&amp;:environment [
+<span id="L420" class="LineNr"> 420 </span>  <span class="Constant">local-scope</span>
+<span id="L421" class="LineNr"> 421 </span>  <span class="Constant">load-ingredients</span>
+<span id="L422" class="LineNr"> 422 </span>  <span class="Comment"># read all scenarios, pushing them to end of a list of scenarios</span>
+<span id="L423" class="LineNr"> 423 </span>  idx:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L424" class="LineNr"> 424 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L425" class="LineNr"> 425 </span>  <a href='../065duplex_list.mu.html#L36'>prev</a>:&amp;:sandbox <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L426" class="LineNr"> 426 </span>  <span class="Delimiter">{</span>
+<span id="L427" class="LineNr"> 427 </span>  <span class="Conceal">¦</span> filename:text <span class="Special">&lt;-</span> append <span class="Constant">[lesson/]</span>, idx
+<span id="L428" class="LineNr"> 428 </span>  <span class="Conceal">¦</span> contents:text <span class="Special">&lt;-</span> <a href='../088file.mu.html#L38'>slurp</a> <a href='../088file.mu.html#L11'>resources</a>, filename
+<span id="L429" class="LineNr"> 429 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> contents  <span class="Comment"># stop at first error; assuming file didn't exist</span>
+<span id="L430" class="LineNr"> 430 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span>      <span class="Comment"># todo: handle empty sandbox</span>
+<span id="L431" class="LineNr"> 431 </span>  <span class="Conceal">¦</span> <span class="Comment"># create new sandbox for file</span>
+<span id="L432" class="LineNr"> 432 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> new <span class="Constant">sandbox:type</span>
+<span id="L433" class="LineNr"> 433 </span>  <span class="Conceal">¦</span> *curr <span class="Special">&lt;-</span> put *curr, <span class="Constant">data:offset</span>, contents
+<span id="L434" class="LineNr"> 434 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> <a href='005-sandbox.mu.html#L434'>&lt;end-restore-sandbox&gt;</a></span>
+<span id="L435" class="LineNr"> 435 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L436" class="LineNr"> 436 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> idx
+<span id="L437" class="LineNr"> 437 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">sandbox:offset</span>, curr
+<span id="L438" class="LineNr"> 438 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L439" class="LineNr"> 439 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L440" class="LineNr"> 440 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> idx
+<span id="L441" class="LineNr"> 441 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *prev <span class="Special">&lt;-</span> put *prev, <span class="Constant">next-sandbox:offset</span>, curr
+<span id="L442" class="LineNr"> 442 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L443" class="LineNr"> 443 </span>  <span class="Conceal">¦</span> idx <span class="Special">&lt;-</span> add idx,<span class="Constant"> 1</span>
+<span id="L444" class="LineNr"> 444 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L36'>prev</a> <span class="Special">&lt;-</span> copy curr
+<span id="L445" class="LineNr"> 445 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L446" class="LineNr"> 446 </span>  <span class="Delimiter">}</span>
+<span id="L447" class="LineNr"> 447 </span>  <span class="Comment"># update sandbox count</span>
+<span id="L448" class="LineNr"> 448 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">number-of-sandboxes:offset</span>, idx
+<span id="L449" class="LineNr"> 449 </span>]
+<span id="L450" class="LineNr"> 450 </span>
+<span id="L451" class="LineNr"> 451 </span><span class="Comment"># print the fake sandbox screen to 'screen' with appropriate delimiters</span>
+<span id="L452" class="LineNr"> 452 </span><span class="Comment"># leave cursor at start of next line</span>
+<span id="L453" class="LineNr"> 453 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L453'>render-screen</a> <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a>, sandbox-screen:&amp;:<a href='../081print.mu.html#L4'>screen</a>, left:num, right:num, row:num<span class="muRecipe"> -&gt; </span>row:num, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a> [
+<span id="L454" class="LineNr"> 454 </span>  <span class="Constant">local-scope</span>
+<span id="L455" class="LineNr"> 455 </span>  <span class="Constant">load-ingredients</span>
+<span id="L456" class="LineNr"> 456 </span>  <span class="muControl">return-unless</span> sandbox-screen
+<span id="L457" class="LineNr"> 457 </span>  <span class="Comment"># print 'screen:'</span>
+<span id="L458" class="LineNr"> 458 </span>  row <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[screen:]</span>, left, right, <span class="Constant">245/grey</span>, row
+<span id="L459" class="LineNr"> 459 </span>  <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, left
+<span id="L460" class="LineNr"> 460 </span>  <span class="Comment"># start printing sandbox-screen</span>
+<span id="L461" class="LineNr"> 461 </span>  column:num <span class="Special">&lt;-</span> copy left
+<span id="L462" class="LineNr"> 462 </span>  s-width:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L581'>screen-width</a> sandbox-screen
+<span id="L463" class="LineNr"> 463 </span>  s-height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> sandbox-screen
+<span id="L464" class="LineNr"> 464 </span>  buf:&amp;:@:<a href='../081print.mu.html#L12'>screen-cell</a> <span class="Special">&lt;-</span> get *sandbox-screen, <span class="Constant">data:offset</span>
+<span id="L465" class="LineNr"> 465 </span>  stop-printing:num <span class="Special">&lt;-</span> add left, s-width,<span class="Constant"> 3</span>
+<span id="L466" class="LineNr"> 466 </span>  max-column:num <span class="Special">&lt;-</span> min stop-printing, right
+<span id="L467" class="LineNr"> 467 </span>  i:num <span class="Special">&lt;-</span> copy<span class="Constant"> 0</span>
+<span id="L468" class="LineNr"> 468 </span>  len:num <span class="Special">&lt;-</span> length *buf
+<span id="L469" class="LineNr"> 469 </span>  <a href='../081print.mu.html#L594'>screen-height</a>:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L470" class="LineNr"> 470 </span>  <span class="Delimiter">{</span>
+<span id="L471" class="LineNr"> 471 </span>  <span class="Conceal">¦</span> done?:bool <span class="Special">&lt;-</span> greater-or-equal i, len
 <span id="L472" class="LineNr"> 472 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
-<span id="L473" class="LineNr"> 473 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
-<span id="L474" class="LineNr"> 474 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
-<span id="L475" class="LineNr"> 475 </span>  <span class="Conceal">¦</span> <span class="Comment"># initial leader for each row: two spaces and a '.'</span>
-<span id="L476" class="LineNr"> 476 </span>  <span class="Conceal">¦</span> space:char <span class="Special">&lt;-</span> copy <span class="Constant">32/space</span>
-<span id="L477" class="LineNr"> 477 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space, <span class="Constant">245/grey</span>
-<span id="L478" class="LineNr"> 478 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space, <span class="Constant">245/grey</span>
-<span id="L479" class="LineNr"> 479 </span>  <span class="Conceal">¦</span> full-stop:char <span class="Special">&lt;-</span> copy <span class="Constant">46/period</span>
-<span id="L480" class="LineNr"> 480 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, full-stop, <span class="Constant">245/grey</span>
-<span id="L481" class="LineNr"> 481 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add left,<span class="Constant"> 3</span>
-<span id="L482" class="LineNr"> 482 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L483" class="LineNr"> 483 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print row</span>
-<span id="L484" class="LineNr"> 484 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row-done?:bool <span class="Special">&lt;-</span> greater-or-equal column, max-column
-<span id="L485" class="LineNr"> 485 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> row-done?
-<span id="L486" class="LineNr"> 486 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr:<a href='../081print.mu.html#L12'>screen-cell</a> <span class="Special">&lt;-</span> index *buf, i
-<span id="L487" class="LineNr"> 487 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get curr, <span class="Constant">contents:offset</span>
-<span id="L488" class="LineNr"> 488 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> color:num <span class="Special">&lt;-</span> get curr, <span class="Constant">color:offset</span>
-<span id="L489" class="LineNr"> 489 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L490" class="LineNr"> 490 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># damp whites down to grey</span>
-<span id="L491" class="LineNr"> 491 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> white?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">7/white</span>
-<span id="L492" class="LineNr"> 492 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> white?
-<span id="L493" class="LineNr"> 493 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> color <span class="Special">&lt;-</span> copy <span class="Constant">245/grey</span>
-<span id="L494" class="LineNr"> 494 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L495" class="LineNr"> 495 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
-<span id="L496" class="LineNr"> 496 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
-<span id="L497" class="LineNr"> 497 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
-<span id="L498" class="LineNr"> 498 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L499" class="LineNr"> 499 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L500" class="LineNr"> 500 </span>  <span class="Conceal">¦</span> <span class="Comment"># print final '.'</span>
-<span id="L501" class="LineNr"> 501 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, full-stop, <span class="Constant">245/grey</span>
-<span id="L502" class="LineNr"> 502 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
-<span id="L503" class="LineNr"> 503 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L504" class="LineNr"> 504 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of current line</span>
-<span id="L505" class="LineNr"> 505 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> line-done?:bool <span class="Special">&lt;-</span> greater-than column, right
-<span id="L506" class="LineNr"> 506 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> line-done?
-<span id="L507" class="LineNr"> 507 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space
-<span id="L508" class="LineNr"> 508 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
-<span id="L509" class="LineNr"> 509 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L510" class="LineNr"> 510 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L511" class="LineNr"> 511 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
-<span id="L512" class="LineNr"> 512 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L513" class="LineNr"> 513 </span>  <span class="Delimiter">}</span>
-<span id="L514" class="LineNr"> 514 </span>]
-<span id="L515" class="LineNr"> 515 </span>
-<span id="L516" class="LineNr"> 516 </span><span class="muScenario">scenario</span> run-updates-results [
-<span id="L517" class="LineNr"> 517 </span>  <span class="Constant">local-scope</span>
-<span id="L518" class="LineNr"> 518 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L519" class="LineNr"> 519 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">12/height</span>
-<span id="L520" class="LineNr"> 520 </span>  <span class="Comment"># define a recipe (no indent for the 'add' line below so column numbers are more obvious)</span>
-<span id="L521" class="LineNr"> 521 </span>  assume-resources [
-<span id="L522" class="LineNr"> 522 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L523" class="LineNr"> 523 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> ||</span>
-<span id="L524" class="LineNr"> 524 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
-<span id="L525" class="LineNr"> 525 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  local-scope|</span>
-<span id="L526" class="LineNr"> 526 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  z:num &lt;- add 2, 2|</span>
-<span id="L527" class="LineNr"> 527 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  reply z|</span>
-<span id="L528" class="LineNr"> 528 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
-<span id="L529" class="LineNr"> 529 </span>  <span class="Conceal">¦</span> ]
-<span id="L530" class="LineNr"> 530 </span>  ]
-<span id="L531" class="LineNr"> 531 </span>  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
-<span id="L532" class="LineNr"> 532 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[foo]</span>  <span class="Comment"># contents of sandbox editor</span>
-<span id="L533" class="LineNr"> 533 </span>  <span class="Comment"># run the code in the editors</span>
-<span id="L534" class="LineNr"> 534 </span>  assume-console [
-<span id="L535" class="LineNr"> 535 </span>  <span class="Conceal">¦</span> press F4
-<span id="L536" class="LineNr"> 536 </span>  ]
-<span id="L537" class="LineNr"> 537 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L538" class="LineNr"> 538 </span>  screen-should-contain [
-<span id="L539" class="LineNr"> 539 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L540" class="LineNr"> 540 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L541" class="LineNr"> 541 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎─────────────────────────────────────────────────.</span>
-<span id="L542" class="LineNr"> 542 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎0   edit          copy            delete         .</span>
-<span id="L543" class="LineNr"> 543 </span>  <span class="Conceal">¦</span><span class="Constant"> .  z:num &lt;- add 2, 2                               ╎foo                                              .</span>
-<span id="L544" class="LineNr"> 544 </span>  <span class="Conceal">¦</span><span class="Constant"> .  reply z                                         ╎4                                                .</span>
-<span id="L545" class="LineNr"> 545 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎─────────────────────────────────────────────────.</span>
-<span id="L546" class="LineNr"> 546 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L547" class="LineNr"> 547 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L473" class="LineNr"> 473 </span>  <span class="Conceal">¦</span> done? <span class="Special">&lt;-</span> greater-or-equal row, <a href='../081print.mu.html#L594'>screen-height</a>
+<span id="L474" class="LineNr"> 474 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> done?
+<span id="L475" class="LineNr"> 475 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> copy left
+<span id="L476" class="LineNr"> 476 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, row, column
+<span id="L477" class="LineNr"> 477 </span>  <span class="Conceal">¦</span> <span class="Comment"># initial leader for each row: two spaces and a '.'</span>
+<span id="L478" class="LineNr"> 478 </span>  <span class="Conceal">¦</span> space:char <span class="Special">&lt;-</span> copy <span class="Constant">32/space</span>
+<span id="L479" class="LineNr"> 479 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space, <span class="Constant">245/grey</span>
+<span id="L480" class="LineNr"> 480 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space, <span class="Constant">245/grey</span>
+<span id="L481" class="LineNr"> 481 </span>  <span class="Conceal">¦</span> full-stop:char <span class="Special">&lt;-</span> copy <span class="Constant">46/period</span>
+<span id="L482" class="LineNr"> 482 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, full-stop, <span class="Constant">245/grey</span>
+<span id="L483" class="LineNr"> 483 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add left,<span class="Constant"> 3</span>
+<span id="L484" class="LineNr"> 484 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L485" class="LineNr"> 485 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># print row</span>
+<span id="L486" class="LineNr"> 486 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row-done?:bool <span class="Special">&lt;-</span> greater-or-equal column, max-column
+<span id="L487" class="LineNr"> 487 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> row-done?
+<span id="L488" class="LineNr"> 488 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> curr:<a href='../081print.mu.html#L12'>screen-cell</a> <span class="Special">&lt;-</span> index *buf, i
+<span id="L489" class="LineNr"> 489 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get curr, <span class="Constant">contents:offset</span>
+<span id="L490" class="LineNr"> 490 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> color:num <span class="Special">&lt;-</span> get curr, <span class="Constant">color:offset</span>
+<span id="L491" class="LineNr"> 491 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L492" class="LineNr"> 492 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># damp whites down to grey</span>
+<span id="L493" class="LineNr"> 493 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> white?:bool <span class="Special">&lt;-</span> equal color, <span class="Constant">7/white</span>
+<span id="L494" class="LineNr"> 494 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> white?
+<span id="L495" class="LineNr"> 495 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Conceal">¦</span> color <span class="Special">&lt;-</span> copy <span class="Constant">245/grey</span>
+<span id="L496" class="LineNr"> 496 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L497" class="LineNr"> 497 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, c, color
+<span id="L498" class="LineNr"> 498 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
+<span id="L499" class="LineNr"> 499 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> i <span class="Special">&lt;-</span> add i,<span class="Constant"> 1</span>
+<span id="L500" class="LineNr"> 500 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L501" class="LineNr"> 501 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L502" class="LineNr"> 502 </span>  <span class="Conceal">¦</span> <span class="Comment"># print final '.'</span>
+<span id="L503" class="LineNr"> 503 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, full-stop, <span class="Constant">245/grey</span>
+<span id="L504" class="LineNr"> 504 </span>  <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
+<span id="L505" class="LineNr"> 505 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L506" class="LineNr"> 506 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Comment"># clear rest of current line</span>
+<span id="L507" class="LineNr"> 507 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> line-done?:bool <span class="Special">&lt;-</span> greater-than column, right
+<span id="L508" class="LineNr"> 508 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> line-done?
+<span id="L509" class="LineNr"> 509 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, space
+<span id="L510" class="LineNr"> 510 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> column <span class="Special">&lt;-</span> add column,<span class="Constant"> 1</span>
+<span id="L511" class="LineNr"> 511 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L512" class="LineNr"> 512 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L513" class="LineNr"> 513 </span>  <span class="Conceal">¦</span> row <span class="Special">&lt;-</span> add row,<span class="Constant"> 1</span>
+<span id="L514" class="LineNr"> 514 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L515" class="LineNr"> 515 </span>  <span class="Delimiter">}</span>
+<span id="L516" class="LineNr"> 516 </span>]
+<span id="L517" class="LineNr"> 517 </span>
+<span id="L518" class="LineNr"> 518 </span><span class="muScenario">scenario</span> run-updates-results [
+<span id="L519" class="LineNr"> 519 </span>  <span class="Constant">local-scope</span>
+<span id="L520" class="LineNr"> 520 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L521" class="LineNr"> 521 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">12/height</span>
+<span id="L522" class="LineNr"> 522 </span>  <span class="Comment"># define a recipe (no indent for the 'add' line below so column numbers are more obvious)</span>
+<span id="L523" class="LineNr"> 523 </span>  assume-resources [
+<span id="L524" class="LineNr"> 524 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L525" class="LineNr"> 525 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> ||</span>
+<span id="L526" class="LineNr"> 526 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">|recipe</span> foo <span class="Constant">[|</span>
+<span id="L527" class="LineNr"> 527 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  local-scope|</span>
+<span id="L528" class="LineNr"> 528 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  z:num &lt;- add 2, 2|</span>
+<span id="L529" class="LineNr"> 529 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |  reply z|</span>
+<span id="L530" class="LineNr"> 530 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> </span><span class="Conceal">¦</span><span class="Constant"> |]</span>|
+<span id="L531" class="LineNr"> 531 </span>  <span class="Conceal">¦</span> ]
+<span id="L532" class="LineNr"> 532 </span>  ]
+<span id="L533" class="LineNr"> 533 </span>  <span class="Comment"># sandbox editor contains an instruction without storing outputs</span>
+<span id="L534" class="LineNr"> 534 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[foo]</span>  <span class="Comment"># contents of sandbox editor</span>
+<span id="L535" class="LineNr"> 535 </span>  <span class="Comment"># run the code in the editors</span>
+<span id="L536" class="LineNr"> 536 </span>  assume-console [
+<span id="L537" class="LineNr"> 537 </span>  <span class="Conceal">¦</span> press F4
+<span id="L538" class="LineNr"> 538 </span>  ]
+<span id="L539" class="LineNr"> 539 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L540" class="LineNr"> 540 </span>  screen-should-contain [
+<span id="L541" class="LineNr"> 541 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L542" class="LineNr"> 542 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L543" class="LineNr"> 543 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎─────────────────────────────────────────────────.</span>
+<span id="L544" class="LineNr"> 544 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎0   edit          copy            delete         .</span>
+<span id="L545" class="LineNr"> 545 </span>  <span class="Conceal">¦</span><span class="Constant"> .  z:num &lt;- add 2, 2                               ╎foo                                              .</span>
+<span id="L546" class="LineNr"> 546 </span>  <span class="Conceal">¦</span><span class="Constant"> .  reply z                                         ╎4                                                .</span>
+<span id="L547" class="LineNr"> 547 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎─────────────────────────────────────────────────.</span>
 <span id="L548" class="LineNr"> 548 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L549" class="LineNr"> 549 </span>  ]
-<span id="L550" class="LineNr"> 550 </span>  <span class="Comment"># make a change (incrementing one of the args to 'add'), then rerun</span>
-<span id="L551" class="LineNr"> 551 </span>  assume-console [
-<span id="L552" class="LineNr"> 552 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 4</span>,<span class="Constant"> 28</span>  <span class="Comment"># one past the value of the second arg</span>
-<span id="L553" class="LineNr"> 553 </span>  <span class="Conceal">¦</span> press backspace
-<span id="L554" class="LineNr"> 554 </span>  <span class="Conceal">¦</span> type <span class="Constant">[3]</span>
-<span id="L555" class="LineNr"> 555 </span>  <span class="Conceal">¦</span> press F4
-<span id="L556" class="LineNr"> 556 </span>  ]
-<span id="L557" class="LineNr"> 557 </span>  run [
-<span id="L558" class="LineNr"> 558 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L559" class="LineNr"> 559 </span>  ]
-<span id="L560" class="LineNr"> 560 </span>  <span class="Comment"># check that screen updates the result on the right</span>
-<span id="L561" class="LineNr"> 561 </span>  screen-should-contain [
-<span id="L562" class="LineNr"> 562 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L563" class="LineNr"> 563 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L564" class="LineNr"> 564 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎─────────────────────────────────────────────────.</span>
-<span id="L565" class="LineNr"> 565 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎0   edit          copy            delete         .</span>
-<span id="L566" class="LineNr"> 566 </span>  <span class="Conceal">¦</span><span class="Constant"> .  z:num &lt;- add 2, 3                               ╎foo                                              .</span>
-<span id="L567" class="LineNr"> 567 </span>  <span class="Conceal">¦</span><span class="Constant"> .  reply z                                         ╎5                                                .</span>
-<span id="L568" class="LineNr"> 568 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎─────────────────────────────────────────────────.</span>
-<span id="L569" class="LineNr"> 569 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L570" class="LineNr"> 570 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L549" class="LineNr"> 549 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L550" class="LineNr"> 550 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L551" class="LineNr"> 551 </span>  ]
+<span id="L552" class="LineNr"> 552 </span>  <span class="Comment"># make a change (incrementing one of the args to 'add'), then rerun</span>
+<span id="L553" class="LineNr"> 553 </span>  assume-console [
+<span id="L554" class="LineNr"> 554 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 4</span>,<span class="Constant"> 28</span>  <span class="Comment"># one past the value of the second arg</span>
+<span id="L555" class="LineNr"> 555 </span>  <span class="Conceal">¦</span> press backspace
+<span id="L556" class="LineNr"> 556 </span>  <span class="Conceal">¦</span> type <span class="Constant">[3]</span>
+<span id="L557" class="LineNr"> 557 </span>  <span class="Conceal">¦</span> press F4
+<span id="L558" class="LineNr"> 558 </span>  ]
+<span id="L559" class="LineNr"> 559 </span>  run [
+<span id="L560" class="LineNr"> 560 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L561" class="LineNr"> 561 </span>  ]
+<span id="L562" class="LineNr"> 562 </span>  <span class="Comment"># check that screen updates the result on the right</span>
+<span id="L563" class="LineNr"> 563 </span>  screen-should-contain [
+<span id="L564" class="LineNr"> 564 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L565" class="LineNr"> 565 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L566" class="LineNr"> 566 </span>  <span class="Conceal">¦</span><span class="Constant"> .recipe foo [                                      ╎─────────────────────────────────────────────────.</span>
+<span id="L567" class="LineNr"> 567 </span>  <span class="Conceal">¦</span><span class="Constant"> .  local-scope                                     ╎0   edit          copy            delete         .</span>
+<span id="L568" class="LineNr"> 568 </span>  <span class="Conceal">¦</span><span class="Constant"> .  z:num &lt;- add 2, 3                               ╎foo                                              .</span>
+<span id="L569" class="LineNr"> 569 </span>  <span class="Conceal">¦</span><span class="Constant"> .  reply z                                         ╎5                                                .</span>
+<span id="L570" class="LineNr"> 570 </span>  <span class="Conceal">¦</span><span class="Constant"> .]                                                 ╎─────────────────────────────────────────────────.</span>
 <span id="L571" class="LineNr"> 571 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L572" class="LineNr"> 572 </span>  ]
-<span id="L573" class="LineNr"> 573 </span>]
-<span id="L574" class="LineNr"> 574 </span>
-<span id="L575" class="LineNr"> 575 </span><span class="muScenario">scenario</span> run-instruction-manages-screen-per-sandbox [
-<span id="L576" class="LineNr"> 576 </span>  <span class="Constant">local-scope</span>
-<span id="L577" class="LineNr"> 577 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L578" class="LineNr"> 578 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
-<span id="L579" class="LineNr"> 579 </span>  <span class="Comment"># empty recipes</span>
-<span id="L580" class="LineNr"> 580 </span>  assume-resources [
-<span id="L581" class="LineNr"> 581 </span>  ]
-<span id="L582" class="LineNr"> 582 </span>  <span class="Comment"># sandbox editor contains an instruction</span>
-<span id="L583" class="LineNr"> 583 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[print <a href='../081print.mu.html#L4'>screen</a>, 4]</span>  <span class="Comment"># contents of sandbox editor</span>
-<span id="L584" class="LineNr"> 584 </span>  <span class="Comment"># run the code in the editor</span>
-<span id="L585" class="LineNr"> 585 </span>  assume-console [
-<span id="L586" class="LineNr"> 586 </span>  <span class="Conceal">¦</span> press F4
-<span id="L587" class="LineNr"> 587 </span>  ]
-<span id="L588" class="LineNr"> 588 </span>  run [
-<span id="L589" class="LineNr"> 589 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L590" class="LineNr"> 590 </span>  ]
-<span id="L591" class="LineNr"> 591 </span>  <span class="Comment"># check that it prints a little toy screen</span>
-<span id="L592" class="LineNr"> 592 </span>  screen-should-contain [
-<span id="L593" class="LineNr"> 593 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L594" class="LineNr"> 594 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L595" class="LineNr"> 595 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L596" class="LineNr"> 596 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L597" class="LineNr"> 597 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎print <a href='../081print.mu.html#L4'>screen</a>, 4                                  .</span>
-<span id="L598" class="LineNr"> 598 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎screen:                                          .</span>
-<span id="L599" class="LineNr"> 599 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .4                             .               .</span>
-<span id="L600" class="LineNr"> 600 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
-<span id="L601" class="LineNr"> 601 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
+<span id="L572" class="LineNr"> 572 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L573" class="LineNr"> 573 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L574" class="LineNr"> 574 </span>  ]
+<span id="L575" class="LineNr"> 575 </span>]
+<span id="L576" class="LineNr"> 576 </span>
+<span id="L577" class="LineNr"> 577 </span><span class="muScenario">scenario</span> run-instruction-manages-screen-per-sandbox [
+<span id="L578" class="LineNr"> 578 </span>  <span class="Constant">local-scope</span>
+<span id="L579" class="LineNr"> 579 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L580" class="LineNr"> 580 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">20/height</span>
+<span id="L581" class="LineNr"> 581 </span>  <span class="Comment"># empty recipes</span>
+<span id="L582" class="LineNr"> 582 </span>  assume-resources [
+<span id="L583" class="LineNr"> 583 </span>  ]
+<span id="L584" class="LineNr"> 584 </span>  <span class="Comment"># sandbox editor contains an instruction</span>
+<span id="L585" class="LineNr"> 585 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[print <a href='../081print.mu.html#L4'>screen</a>, 4]</span>  <span class="Comment"># contents of sandbox editor</span>
+<span id="L586" class="LineNr"> 586 </span>  <span class="Comment"># run the code in the editor</span>
+<span id="L587" class="LineNr"> 587 </span>  assume-console [
+<span id="L588" class="LineNr"> 588 </span>  <span class="Conceal">¦</span> press F4
+<span id="L589" class="LineNr"> 589 </span>  ]
+<span id="L590" class="LineNr"> 590 </span>  run [
+<span id="L591" class="LineNr"> 591 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L592" class="LineNr"> 592 </span>  ]
+<span id="L593" class="LineNr"> 593 </span>  <span class="Comment"># check that it prints a little toy screen</span>
+<span id="L594" class="LineNr"> 594 </span>  screen-should-contain [
+<span id="L595" class="LineNr"> 595 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L596" class="LineNr"> 596 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L597" class="LineNr"> 597 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L598" class="LineNr"> 598 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L599" class="LineNr"> 599 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎print <a href='../081print.mu.html#L4'>screen</a>, 4                                  .</span>
+<span id="L600" class="LineNr"> 600 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎screen:                                          .</span>
+<span id="L601" class="LineNr"> 601 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .4                             .               .</span>
 <span id="L602" class="LineNr"> 602 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
 <span id="L603" class="LineNr"> 603 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
-<span id="L604" class="LineNr"> 604 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L605" class="LineNr"> 605 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L606" class="LineNr"> 606 </span>  ]
-<span id="L607" class="LineNr"> 607 </span>]
-<span id="L608" class="LineNr"> 608 </span>
-<span id="L609" class="LineNr"> 609 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L609'>editor-contents</a> editor:&amp;:editor<span class="muRecipe"> -&gt; </span>result:text [
-<span id="L610" class="LineNr"> 610 </span>  <span class="Constant">local-scope</span>
-<span id="L611" class="LineNr"> 611 </span>  <span class="Constant">load-ingredients</span>
-<span id="L612" class="LineNr"> 612 </span>  buf:&amp;:<a href='../061text.mu.html#L127'>buffer</a> <span class="Special">&lt;-</span> <a href='../061text.mu.html#L132'>new-buffer</a><span class="Constant"> 80</span>
-<span id="L613" class="LineNr"> 613 </span>  curr:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
-<span id="L614" class="LineNr"> 614 </span>  <span class="Comment"># skip § sentinel</span>
-<span id="L615" class="LineNr"> 615 </span>  assert curr, <span class="Constant">[editor without data is illegal; must have at least a sentinel]</span>
-<span id="L616" class="LineNr"> 616 </span>  curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L617" class="LineNr"> 617 </span>  <span class="muControl">return-unless</span> curr,<span class="Constant"> 0</span>
-<span id="L618" class="LineNr"> 618 </span>  <span class="Delimiter">{</span>
-<span id="L619" class="LineNr"> 619 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
-<span id="L620" class="LineNr"> 620 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
-<span id="L621" class="LineNr"> 621 </span>  <span class="Conceal">¦</span> buf <span class="Special">&lt;-</span> append buf, c
-<span id="L622" class="LineNr"> 622 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
-<span id="L623" class="LineNr"> 623 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L624" class="LineNr"> 624 </span>  <span class="Delimiter">}</span>
-<span id="L625" class="LineNr"> 625 </span>  result <span class="Special">&lt;-</span> <a href='../061text.mu.html#L329'>buffer-to-array</a> buf
-<span id="L626" class="LineNr"> 626 </span>]
-<span id="L627" class="LineNr"> 627 </span>
-<span id="L628" class="LineNr"> 628 </span><span class="muScenario">scenario</span> editor-provides-edited-contents [
-<span id="L629" class="LineNr"> 629 </span>  <span class="Constant">local-scope</span>
-<span id="L630" class="LineNr"> 630 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
-<span id="L631" class="LineNr"> 631 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
-<span id="L632" class="LineNr"> 632 </span>  assume-console [
-<span id="L633" class="LineNr"> 633 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 2</span>
-<span id="L634" class="LineNr"> 634 </span>  <span class="Conceal">¦</span> type <span class="Constant">[def]</span>
-<span id="L635" class="LineNr"> 635 </span>  ]
-<span id="L636" class="LineNr"> 636 </span>  run [
-<span id="L637" class="LineNr"> 637 </span>  <span class="Conceal">¦</span> <a href='002-typing.mu.html#L14'>editor-event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, e
-<span id="L638" class="LineNr"> 638 </span>  <span class="Conceal">¦</span> s:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L609'>editor-contents</a> e
-<span id="L639" class="LineNr"> 639 </span>  <span class="Conceal">¦</span> 1:@:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> copy *s
-<span id="L640" class="LineNr"> 640 </span>  ]
-<span id="L641" class="LineNr"> 641 </span>  memory-should-contain [
-<span id="L642" class="LineNr"> 642 </span>  <span class="Conceal">¦</span> 1:array:character <span class="Special">&lt;-</span> <span class="Constant">[abdefc]</span>
-<span id="L643" class="LineNr"> 643 </span>  ]
-<span id="L644" class="LineNr"> 644 </span>]
-<span id="L645" class="LineNr"> 645 </span>
-<span id="L646" class="LineNr"> 646 </span><span class="Comment"># keep the bottom of recipes from scrolling off the screen</span>
+<span id="L604" class="LineNr"> 604 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
+<span id="L605" class="LineNr"> 605 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎  .                              .               .</span>
+<span id="L606" class="LineNr"> 606 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L607" class="LineNr"> 607 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L608" class="LineNr"> 608 </span>  ]
+<span id="L609" class="LineNr"> 609 </span>]
+<span id="L610" class="LineNr"> 610 </span>
+<span id="L611" class="LineNr"> 611 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L611'>editor-contents</a> editor:&amp;:editor<span class="muRecipe"> -&gt; </span>result:text [
+<span id="L612" class="LineNr"> 612 </span>  <span class="Constant">local-scope</span>
+<span id="L613" class="LineNr"> 613 </span>  <span class="Constant">load-ingredients</span>
+<span id="L614" class="LineNr"> 614 </span>  buf:&amp;:<a href='../061text.mu.html#L127'>buffer</a> <span class="Special">&lt;-</span> <a href='../061text.mu.html#L132'>new-buffer</a><span class="Constant"> 80</span>
+<span id="L615" class="LineNr"> 615 </span>  curr:&amp;:duplex-list:char <span class="Special">&lt;-</span> get *editor, <span class="Constant">data:offset</span>
+<span id="L616" class="LineNr"> 616 </span>  <span class="Comment"># skip § sentinel</span>
+<span id="L617" class="LineNr"> 617 </span>  assert curr, <span class="Constant">[editor without data is illegal; must have at least a sentinel]</span>
+<span id="L618" class="LineNr"> 618 </span>  curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L619" class="LineNr"> 619 </span>  <span class="muControl">return-unless</span> curr,<span class="Constant"> 0</span>
+<span id="L620" class="LineNr"> 620 </span>  <span class="Delimiter">{</span>
+<span id="L621" class="LineNr"> 621 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> curr
+<span id="L622" class="LineNr"> 622 </span>  <span class="Conceal">¦</span> c:char <span class="Special">&lt;-</span> get *curr, <span class="Constant">value:offset</span>
+<span id="L623" class="LineNr"> 623 </span>  <span class="Conceal">¦</span> buf <span class="Special">&lt;-</span> append buf, c
+<span id="L624" class="LineNr"> 624 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> <a href='../065duplex_list.mu.html#L29'>next</a> curr
+<span id="L625" class="LineNr"> 625 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L626" class="LineNr"> 626 </span>  <span class="Delimiter">}</span>
+<span id="L627" class="LineNr"> 627 </span>  result <span class="Special">&lt;-</span> <a href='../061text.mu.html#L329'>buffer-to-array</a> buf
+<span id="L628" class="LineNr"> 628 </span>]
+<span id="L629" class="LineNr"> 629 </span>
+<span id="L630" class="LineNr"> 630 </span><span class="muScenario">scenario</span> editor-provides-edited-contents [
+<span id="L631" class="LineNr"> 631 </span>  <span class="Constant">local-scope</span>
+<span id="L632" class="LineNr"> 632 </span>  assume-screen <span class="Constant">10/width</span>, <span class="Constant">5/height</span>
+<span id="L633" class="LineNr"> 633 </span>  e:&amp;:editor <span class="Special">&lt;-</span> <a href='001-editor.mu.html#L52'>new-editor</a> <span class="Constant">[abc]</span>, <span class="Constant">0/left</span>, <span class="Constant">10/right</span>
+<span id="L634" class="LineNr"> 634 </span>  assume-console [
+<span id="L635" class="LineNr"> 635 </span>  <span class="Conceal">¦</span> left-click<span class="Constant"> 1</span>,<span class="Constant"> 2</span>
+<span id="L636" class="LineNr"> 636 </span>  <span class="Conceal">¦</span> type <span class="Constant">[def]</span>
+<span id="L637" class="LineNr"> 637 </span>  ]
+<span id="L638" class="LineNr"> 638 </span>  run [
+<span id="L639" class="LineNr"> 639 </span>  <span class="Conceal">¦</span> <a href='002-typing.mu.html#L14'>editor-event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, e
+<span id="L640" class="LineNr"> 640 </span>  <span class="Conceal">¦</span> s:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L611'>editor-contents</a> e
+<span id="L641" class="LineNr"> 641 </span>  <span class="Conceal">¦</span> 1:@:char/<span class="Special">raw</span> <span class="Special">&lt;-</span> copy *s
+<span id="L642" class="LineNr"> 642 </span>  ]
+<span id="L643" class="LineNr"> 643 </span>  memory-should-contain [
+<span id="L644" class="LineNr"> 644 </span>  <span class="Conceal">¦</span> 1:array:character <span class="Special">&lt;-</span> <span class="Constant">[abdefc]</span>
+<span id="L645" class="LineNr"> 645 </span>  ]
+<span id="L646" class="LineNr"> 646 </span>]
 <span id="L647" class="LineNr"> 647 </span>
-<span id="L648" class="LineNr"> 648 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor [
-<span id="L649" class="LineNr"> 649 </span>  <span class="Constant">local-scope</span>
-<span id="L650" class="LineNr"> 650 </span>  trace-until <span class="Constant">100/app</span>
-<span id="L651" class="LineNr"> 651 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L652" class="LineNr"> 652 </span>  assume-resources [
-<span id="L653" class="LineNr"> 653 </span>  ]
-<span id="L654" class="LineNr"> 654 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L655" class="LineNr"> 655 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L656" class="LineNr"> 656 </span>  assume-console [
-<span id="L657" class="LineNr"> 657 </span>  <span class="Conceal">¦</span> press enter
-<span id="L658" class="LineNr"> 658 </span>  <span class="Conceal">¦</span> press down-arrow
-<span id="L659" class="LineNr"> 659 </span>  ]
-<span id="L660" class="LineNr"> 660 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L661" class="LineNr"> 661 </span>  <span class="Comment"># no scroll</span>
-<span id="L662" class="LineNr"> 662 </span>  screen-should-contain [
-<span id="L663" class="LineNr"> 663 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L664" class="LineNr"> 664 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L665" class="LineNr"> 665 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L666" class="LineNr"> 666 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L667" class="LineNr"> 667 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L668" class="LineNr"> 668 </span>  ]
-<span id="L669" class="LineNr"> 669 </span>]
-<span id="L670" class="LineNr"> 670 </span>
-<span id="L671" class="LineNr"> 671 </span><span class="muScenario">scenario</span> cursor-down-in-recipe-editor [
-<span id="L672" class="LineNr"> 672 </span>  <span class="Constant">local-scope</span>
-<span id="L673" class="LineNr"> 673 </span>  trace-until <span class="Constant">100/app</span>
-<span id="L674" class="LineNr"> 674 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L675" class="LineNr"> 675 </span>  assume-resources [
-<span id="L676" class="LineNr"> 676 </span>  ]
-<span id="L677" class="LineNr"> 677 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L678" class="LineNr"> 678 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L679" class="LineNr"> 679 </span>  assume-console [
-<span id="L680" class="LineNr"> 680 </span>  <span class="Conceal">¦</span> press enter
-<span id="L681" class="LineNr"> 681 </span>  <span class="Conceal">¦</span> press up-arrow
-<span id="L682" class="LineNr"> 682 </span>  <span class="Conceal">¦</span> press down-arrow  <span class="Comment"># while cursor isn't at bottom</span>
-<span id="L683" class="LineNr"> 683 </span>  ]
-<span id="L684" class="LineNr"> 684 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L685" class="LineNr"> 685 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L686" class="LineNr"> 686 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L687" class="LineNr"> 687 </span>  <span class="Comment"># cursor moves back to bottom</span>
-<span id="L688" class="LineNr"> 688 </span>  screen-should-contain [
-<span id="L689" class="LineNr"> 689 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L690" class="LineNr"> 690 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L691" class="LineNr"> 691 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣                                                 ╎─────────────────────────────────────────────────.</span>
-<span id="L692" class="LineNr"> 692 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L693" class="LineNr"> 693 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L694" class="LineNr"> 694 </span>  ]
-<span id="L695" class="LineNr"> 695 </span>]
-<span id="L696" class="LineNr"> 696 </span>
-<span id="L697" class="LineNr"> 697 </span><span class="Comment"># we'll not use the recipe-editor's 'bottom' element directly, because later</span>
-<span id="L698" class="LineNr"> 698 </span><span class="Comment"># layers will add other stuff to the left side below the editor (error messages)</span>
-<span id="L699" class="LineNr"> 699 </span>
-<span id="L700" class="LineNr"> 700 </span><span class="muData">container</span> environment [
-<span id="L701" class="LineNr"> 701 </span>  recipe-bottom:num
-<span id="L702" class="LineNr"> 702 </span>]
-<span id="L703" class="LineNr"> 703 </span>
-<span id="L704" class="LineNr"> 704 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L488'>&lt;render-recipe-components-end&gt;</a></span> [
-<span id="L705" class="LineNr"> 705 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">recipe-bottom:offset</span>, row
-<span id="L706" class="LineNr"> 706 </span>]
-<span id="L707" class="LineNr"> 707 </span>
-<span id="L708" class="LineNr"> 708 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
-<span id="L709" class="LineNr"> 709 </span>  <span class="Delimiter">{</span>
-<span id="L710" class="LineNr"> 710 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
-<span id="L711" class="LineNr"> 711 </span>  <span class="Conceal">¦</span> down-arrow?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65516/down-arrow</span>
-<span id="L712" class="LineNr"> 712 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> down-arrow?
-<span id="L713" class="LineNr"> 713 </span>  <span class="Conceal">¦</span> recipe-editor:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L714" class="LineNr"> 714 </span>  <span class="Conceal">¦</span> recipe-cursor-row:num <span class="Special">&lt;-</span> get *recipe-editor, <span class="Constant">cursor-row:offset</span>
-<span id="L715" class="LineNr"> 715 </span>  <span class="Conceal">¦</span> recipe-editor-bottom:num <span class="Special">&lt;-</span> get *recipe-editor, <span class="Constant">bottom:offset</span>
-<span id="L716" class="LineNr"> 716 </span>  <span class="Conceal">¦</span> at-bottom-of-editor?:bool <span class="Special">&lt;-</span> greater-or-equal recipe-cursor-row, recipe-editor-bottom
-<span id="L717" class="LineNr"> 717 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-bottom-of-editor?
-<span id="L718" class="LineNr"> 718 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a>:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a> env, <a href='../081print.mu.html#L4'>screen</a>
-<span id="L719" class="LineNr"> 719 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a>
-<span id="L720" class="LineNr"> 720 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L721" class="LineNr"> 721 </span>  <span class="Delimiter">}</span>
-<span id="L722" class="LineNr"> 722 </span>  <span class="Delimiter">{</span>
-<span id="L723" class="LineNr"> 723 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
-<span id="L724" class="LineNr"> 724 </span>  <span class="Conceal">¦</span> page-down?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65518/page-down</span>
-<span id="L725" class="LineNr"> 725 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-down?
-<span id="L726" class="LineNr"> 726 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a>:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a> env, <a href='../081print.mu.html#L4'>screen</a>
-<span id="L727" class="LineNr"> 727 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a>
-<span id="L728" class="LineNr"> 728 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L729" class="LineNr"> 729 </span>  <span class="Delimiter">}</span>
-<span id="L730" class="LineNr"> 730 </span>]
-<span id="L731" class="LineNr"> 731 </span>
-<span id="L732" class="LineNr"> 732 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L66'>&lt;global-type&gt;</a></span> [
-<span id="L733" class="LineNr"> 733 </span>  <span class="Delimiter">{</span>
-<span id="L734" class="LineNr"> 734 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
-<span id="L735" class="LineNr"> 735 </span>  <span class="Conceal">¦</span> page-down?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">6/ctrl-f</span>
-<span id="L736" class="LineNr"> 736 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-down?
-<span id="L737" class="LineNr"> 737 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a>:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a> env, <a href='../081print.mu.html#L4'>screen</a>
-<span id="L738" class="LineNr"> 738 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a>
-<span id="L739" class="LineNr"> 739 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
-<span id="L740" class="LineNr"> 740 </span>  <span class="Delimiter">}</span>
-<span id="L741" class="LineNr"> 741 </span>]
-<span id="L742" class="LineNr"> 742 </span>
-<span id="L743" class="LineNr"> 743 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L743'>more-to-scroll?</a> env:&amp;:environment, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a><span class="muRecipe"> -&gt; </span>result:bool [
-<span id="L744" class="LineNr"> 744 </span>  <span class="Constant">local-scope</span>
-<span id="L745" class="LineNr"> 745 </span>  <span class="Constant">load-ingredients</span>
-<span id="L746" class="LineNr"> 746 </span>  recipe-bottom:num <span class="Special">&lt;-</span> get *env, <span class="Constant">recipe-bottom:offset</span>
-<span id="L747" class="LineNr"> 747 </span>  height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L748" class="LineNr"> 748 </span>  result <span class="Special">&lt;-</span> greater-or-equal recipe-bottom, height
-<span id="L749" class="LineNr"> 749 </span>]
-<span id="L750" class="LineNr"> 750 </span>
-<span id="L751" class="LineNr"> 751 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor-2 [
-<span id="L752" class="LineNr"> 752 </span>  <span class="Constant">local-scope</span>
-<span id="L753" class="LineNr"> 753 </span>  trace-until <span class="Constant">100/app</span>
-<span id="L754" class="LineNr"> 754 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L755" class="LineNr"> 755 </span>  assume-resources [
-<span id="L756" class="LineNr"> 756 </span>  ]
-<span id="L757" class="LineNr"> 757 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L758" class="LineNr"> 758 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L759" class="LineNr"> 759 </span>  assume-console [
-<span id="L760" class="LineNr"> 760 </span>  <span class="Conceal">¦</span> <span class="Comment"># add a line</span>
-<span id="L761" class="LineNr"> 761 </span>  <span class="Conceal">¦</span> press enter
-<span id="L762" class="LineNr"> 762 </span>  <span class="Conceal">¦</span> <span class="Comment"># cursor back to top line</span>
-<span id="L763" class="LineNr"> 763 </span>  <span class="Conceal">¦</span> press up-arrow
-<span id="L764" class="LineNr"> 764 </span>  <span class="Conceal">¦</span> <span class="Comment"># try to scroll</span>
-<span id="L765" class="LineNr"> 765 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>  <span class="Comment"># or ctrl-f</span>
-<span id="L766" class="LineNr"> 766 </span>  ]
-<span id="L767" class="LineNr"> 767 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L768" class="LineNr"> 768 </span>  <span class="Comment"># no scroll, and cursor remains at top line</span>
-<span id="L769" class="LineNr"> 769 </span>  screen-should-contain [
-<span id="L770" class="LineNr"> 770 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L771" class="LineNr"> 771 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L772" class="LineNr"> 772 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L773" class="LineNr"> 773 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
-<span id="L774" class="LineNr"> 774 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L775" class="LineNr"> 775 </span>  ]
-<span id="L776" class="LineNr"> 776 </span>]
-<span id="L777" class="LineNr"> 777 </span>
-<span id="L778" class="LineNr"> 778 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor-3 [
-<span id="L779" class="LineNr"> 779 </span>  <span class="Constant">local-scope</span>
-<span id="L780" class="LineNr"> 780 </span>  trace-until <span class="Constant">100/app</span>
-<span id="L781" class="LineNr"> 781 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L782" class="LineNr"> 782 </span>  assume-resources [
-<span id="L783" class="LineNr"> 783 </span>  ]
-<span id="L784" class="LineNr"> 784 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[ab</span>
-<span id="L785" class="LineNr"> 785 </span><span class="Constant">cd]</span>
-<span id="L786" class="LineNr"> 786 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L787" class="LineNr"> 787 </span>  assume-console [
-<span id="L788" class="LineNr"> 788 </span>  <span class="Conceal">¦</span> <span class="Comment"># add a line</span>
-<span id="L789" class="LineNr"> 789 </span>  <span class="Conceal">¦</span> press enter
-<span id="L790" class="LineNr"> 790 </span>  <span class="Conceal">¦</span> <span class="Comment"># switch to sandbox</span>
-<span id="L791" class="LineNr"> 791 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L792" class="LineNr"> 792 </span>  <span class="Conceal">¦</span> <span class="Comment"># move cursor</span>
-<span id="L793" class="LineNr"> 793 </span>  <span class="Conceal">¦</span> press down-arrow
-<span id="L794" class="LineNr"> 794 </span>  ]
-<span id="L795" class="LineNr"> 795 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L796" class="LineNr"> 796 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L797" class="LineNr"> 797 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L798" class="LineNr"> 798 </span>  <span class="Comment"># no scroll on recipe side, cursor moves on sandbox side</span>
-<span id="L799" class="LineNr"> 799 </span>  screen-should-contain [
-<span id="L800" class="LineNr"> 800 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L801" class="LineNr"> 801 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎ab                                               .</span>
-<span id="L802" class="LineNr"> 802 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣d                                               .</span>
-<span id="L803" class="LineNr"> 803 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L804" class="LineNr"> 804 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L805" class="LineNr"> 805 </span>  ]
-<span id="L806" class="LineNr"> 806 </span>]
-<span id="L807" class="LineNr"> 807 </span>
-<span id="L808" class="LineNr"> 808 </span><span class="Comment"># scrolling through sandboxes</span>
+<span id="L648" class="LineNr"> 648 </span><span class="Comment"># keep the bottom of recipes from scrolling off the screen</span>
+<span id="L649" class="LineNr"> 649 </span>
+<span id="L650" class="LineNr"> 650 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor [
+<span id="L651" class="LineNr"> 651 </span>  <span class="Constant">local-scope</span>
+<span id="L652" class="LineNr"> 652 </span>  trace-until <span class="Constant">100/app</span>
+<span id="L653" class="LineNr"> 653 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L654" class="LineNr"> 654 </span>  assume-resources [
+<span id="L655" class="LineNr"> 655 </span>  ]
+<span id="L656" class="LineNr"> 656 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L657" class="LineNr"> 657 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L658" class="LineNr"> 658 </span>  assume-console [
+<span id="L659" class="LineNr"> 659 </span>  <span class="Conceal">¦</span> press enter
+<span id="L660" class="LineNr"> 660 </span>  <span class="Conceal">¦</span> press down-arrow
+<span id="L661" class="LineNr"> 661 </span>  ]
+<span id="L662" class="LineNr"> 662 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L663" class="LineNr"> 663 </span>  <span class="Comment"># no scroll</span>
+<span id="L664" class="LineNr"> 664 </span>  screen-should-contain [
+<span id="L665" class="LineNr"> 665 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L666" class="LineNr"> 666 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L667" class="LineNr"> 667 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L668" class="LineNr"> 668 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L669" class="LineNr"> 669 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L670" class="LineNr"> 670 </span>  ]
+<span id="L671" class="LineNr"> 671 </span>]
+<span id="L672" class="LineNr"> 672 </span>
+<span id="L673" class="LineNr"> 673 </span><span class="muScenario">scenario</span> cursor-down-in-recipe-editor [
+<span id="L674" class="LineNr"> 674 </span>  <span class="Constant">local-scope</span>
+<span id="L675" class="LineNr"> 675 </span>  trace-until <span class="Constant">100/app</span>
+<span id="L676" class="LineNr"> 676 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L677" class="LineNr"> 677 </span>  assume-resources [
+<span id="L678" class="LineNr"> 678 </span>  ]
+<span id="L679" class="LineNr"> 679 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L680" class="LineNr"> 680 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L681" class="LineNr"> 681 </span>  assume-console [
+<span id="L682" class="LineNr"> 682 </span>  <span class="Conceal">¦</span> press enter
+<span id="L683" class="LineNr"> 683 </span>  <span class="Conceal">¦</span> press up-arrow
+<span id="L684" class="LineNr"> 684 </span>  <span class="Conceal">¦</span> press down-arrow  <span class="Comment"># while cursor isn't at bottom</span>
+<span id="L685" class="LineNr"> 685 </span>  ]
+<span id="L686" class="LineNr"> 686 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L687" class="LineNr"> 687 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L688" class="LineNr"> 688 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L689" class="LineNr"> 689 </span>  <span class="Comment"># cursor moves back to bottom</span>
+<span id="L690" class="LineNr"> 690 </span>  screen-should-contain [
+<span id="L691" class="LineNr"> 691 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L692" class="LineNr"> 692 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L693" class="LineNr"> 693 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣                                                 ╎─────────────────────────────────────────────────.</span>
+<span id="L694" class="LineNr"> 694 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L695" class="LineNr"> 695 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L696" class="LineNr"> 696 </span>  ]
+<span id="L697" class="LineNr"> 697 </span>]
+<span id="L698" class="LineNr"> 698 </span>
+<span id="L699" class="LineNr"> 699 </span><span class="Comment"># we'll not use the recipe-editor's 'bottom' element directly, because later</span>
+<span id="L700" class="LineNr"> 700 </span><span class="Comment"># layers will add other stuff to the left side below the editor (error messages)</span>
+<span id="L701" class="LineNr"> 701 </span>
+<span id="L702" class="LineNr"> 702 </span><span class="muData">container</span> environment [
+<span id="L703" class="LineNr"> 703 </span>  recipe-bottom:num
+<span id="L704" class="LineNr"> 704 </span>]
+<span id="L705" class="LineNr"> 705 </span>
+<span id="L706" class="LineNr"> 706 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L488'>&lt;render-recipe-components-end&gt;</a></span> [
+<span id="L707" class="LineNr"> 707 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">recipe-bottom:offset</span>, row
+<span id="L708" class="LineNr"> 708 </span>]
+<span id="L709" class="LineNr"> 709 </span>
+<span id="L710" class="LineNr"> 710 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
+<span id="L711" class="LineNr"> 711 </span>  <span class="Delimiter">{</span>
+<span id="L712" class="LineNr"> 712 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
+<span id="L713" class="LineNr"> 713 </span>  <span class="Conceal">¦</span> down-arrow?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65516/down-arrow</span>
+<span id="L714" class="LineNr"> 714 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> down-arrow?
+<span id="L715" class="LineNr"> 715 </span>  <span class="Conceal">¦</span> recipe-editor:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
+<span id="L716" class="LineNr"> 716 </span>  <span class="Conceal">¦</span> recipe-cursor-row:num <span class="Special">&lt;-</span> get *recipe-editor, <span class="Constant">cursor-row:offset</span>
+<span id="L717" class="LineNr"> 717 </span>  <span class="Conceal">¦</span> recipe-editor-bottom:num <span class="Special">&lt;-</span> get *recipe-editor, <span class="Constant">bottom:offset</span>
+<span id="L718" class="LineNr"> 718 </span>  <span class="Conceal">¦</span> at-bottom-of-editor?:bool <span class="Special">&lt;-</span> greater-or-equal recipe-cursor-row, recipe-editor-bottom
+<span id="L719" class="LineNr"> 719 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> at-bottom-of-editor?
+<span id="L720" class="LineNr"> 720 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a>:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a> env, <a href='../081print.mu.html#L4'>screen</a>
+<span id="L721" class="LineNr"> 721 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a>
+<span id="L722" class="LineNr"> 722 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L723" class="LineNr"> 723 </span>  <span class="Delimiter">}</span>
+<span id="L724" class="LineNr"> 724 </span>  <span class="Delimiter">{</span>
+<span id="L725" class="LineNr"> 725 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
+<span id="L726" class="LineNr"> 726 </span>  <span class="Conceal">¦</span> page-down?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65518/page-down</span>
+<span id="L727" class="LineNr"> 727 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-down?
+<span id="L728" class="LineNr"> 728 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a>:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a> env, <a href='../081print.mu.html#L4'>screen</a>
+<span id="L729" class="LineNr"> 729 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a>
+<span id="L730" class="LineNr"> 730 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L731" class="LineNr"> 731 </span>  <span class="Delimiter">}</span>
+<span id="L732" class="LineNr"> 732 </span>]
+<span id="L733" class="LineNr"> 733 </span>
+<span id="L734" class="LineNr"> 734 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L66'>&lt;global-type&gt;</a></span> [
+<span id="L735" class="LineNr"> 735 </span>  <span class="Delimiter">{</span>
+<span id="L736" class="LineNr"> 736 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandbox-in-focus?
+<span id="L737" class="LineNr"> 737 </span>  <span class="Conceal">¦</span> page-down?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">6/ctrl-f</span>
+<span id="L738" class="LineNr"> 738 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-down?
+<span id="L739" class="LineNr"> 739 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a>:bool <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a> env, <a href='../081print.mu.html#L4'>screen</a>
+<span id="L740" class="LineNr"> 740 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a>
+<span id="L741" class="LineNr"> 741 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span> <span class="Constant">+next-event</span>
+<span id="L742" class="LineNr"> 742 </span>  <span class="Delimiter">}</span>
+<span id="L743" class="LineNr"> 743 </span>]
+<span id="L744" class="LineNr"> 744 </span>
+<span id="L745" class="LineNr"> 745 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L745'>more-to-scroll?</a> env:&amp;:environment, <a href='../081print.mu.html#L4'>screen</a>:&amp;:<a href='../081print.mu.html#L4'>screen</a><span class="muRecipe"> -&gt; </span>result:bool [
+<span id="L746" class="LineNr"> 746 </span>  <span class="Constant">local-scope</span>
+<span id="L747" class="LineNr"> 747 </span>  <span class="Constant">load-ingredients</span>
+<span id="L748" class="LineNr"> 748 </span>  recipe-bottom:num <span class="Special">&lt;-</span> get *env, <span class="Constant">recipe-bottom:offset</span>
+<span id="L749" class="LineNr"> 749 </span>  height:num <span class="Special">&lt;-</span> <a href='../081print.mu.html#L594'>screen-height</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L750" class="LineNr"> 750 </span>  result <span class="Special">&lt;-</span> greater-or-equal recipe-bottom, height
+<span id="L751" class="LineNr"> 751 </span>]
+<span id="L752" class="LineNr"> 752 </span>
+<span id="L753" class="LineNr"> 753 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor-2 [
+<span id="L754" class="LineNr"> 754 </span>  <span class="Constant">local-scope</span>
+<span id="L755" class="LineNr"> 755 </span>  trace-until <span class="Constant">100/app</span>
+<span id="L756" class="LineNr"> 756 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L757" class="LineNr"> 757 </span>  assume-resources [
+<span id="L758" class="LineNr"> 758 </span>  ]
+<span id="L759" class="LineNr"> 759 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L760" class="LineNr"> 760 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L761" class="LineNr"> 761 </span>  assume-console [
+<span id="L762" class="LineNr"> 762 </span>  <span class="Conceal">¦</span> <span class="Comment"># add a line</span>
+<span id="L763" class="LineNr"> 763 </span>  <span class="Conceal">¦</span> press enter
+<span id="L764" class="LineNr"> 764 </span>  <span class="Conceal">¦</span> <span class="Comment"># cursor back to top line</span>
+<span id="L765" class="LineNr"> 765 </span>  <span class="Conceal">¦</span> press up-arrow
+<span id="L766" class="LineNr"> 766 </span>  <span class="Conceal">¦</span> <span class="Comment"># try to scroll</span>
+<span id="L767" class="LineNr"> 767 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>  <span class="Comment"># or ctrl-f</span>
+<span id="L768" class="LineNr"> 768 </span>  ]
+<span id="L769" class="LineNr"> 769 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L770" class="LineNr"> 770 </span>  <span class="Comment"># no scroll, and cursor remains at top line</span>
+<span id="L771" class="LineNr"> 771 </span>  screen-should-contain [
+<span id="L772" class="LineNr"> 772 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L773" class="LineNr"> 773 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L774" class="LineNr"> 774 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L775" class="LineNr"> 775 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎                                                 .</span>
+<span id="L776" class="LineNr"> 776 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L777" class="LineNr"> 777 </span>  ]
+<span id="L778" class="LineNr"> 778 </span>]
+<span id="L779" class="LineNr"> 779 </span>
+<span id="L780" class="LineNr"> 780 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-recipe-editor-3 [
+<span id="L781" class="LineNr"> 781 </span>  <span class="Constant">local-scope</span>
+<span id="L782" class="LineNr"> 782 </span>  trace-until <span class="Constant">100/app</span>
+<span id="L783" class="LineNr"> 783 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L784" class="LineNr"> 784 </span>  assume-resources [
+<span id="L785" class="LineNr"> 785 </span>  ]
+<span id="L786" class="LineNr"> 786 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[ab</span>
+<span id="L787" class="LineNr"> 787 </span><span class="Constant">cd]</span>
+<span id="L788" class="LineNr"> 788 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L789" class="LineNr"> 789 </span>  assume-console [
+<span id="L790" class="LineNr"> 790 </span>  <span class="Conceal">¦</span> <span class="Comment"># add a line</span>
+<span id="L791" class="LineNr"> 791 </span>  <span class="Conceal">¦</span> press enter
+<span id="L792" class="LineNr"> 792 </span>  <span class="Conceal">¦</span> <span class="Comment"># switch to sandbox</span>
+<span id="L793" class="LineNr"> 793 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L794" class="LineNr"> 794 </span>  <span class="Conceal">¦</span> <span class="Comment"># move cursor</span>
+<span id="L795" class="LineNr"> 795 </span>  <span class="Conceal">¦</span> press down-arrow
+<span id="L796" class="LineNr"> 796 </span>  ]
+<span id="L797" class="LineNr"> 797 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L798" class="LineNr"> 798 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L799" class="LineNr"> 799 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L800" class="LineNr"> 800 </span>  <span class="Comment"># no scroll on recipe side, cursor moves on sandbox side</span>
+<span id="L801" class="LineNr"> 801 </span>  screen-should-contain [
+<span id="L802" class="LineNr"> 802 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L803" class="LineNr"> 803 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎ab                                               .</span>
+<span id="L804" class="LineNr"> 804 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣d                                               .</span>
+<span id="L805" class="LineNr"> 805 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L806" class="LineNr"> 806 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L807" class="LineNr"> 807 </span>  ]
+<span id="L808" class="LineNr"> 808 </span>]
 <span id="L809" class="LineNr"> 809 </span>
-<span id="L810" class="LineNr"> 810 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-sandbox-editor [
-<span id="L811" class="LineNr"> 811 </span>  <span class="Constant">local-scope</span>
-<span id="L812" class="LineNr"> 812 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L813" class="LineNr"> 813 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L814" class="LineNr"> 814 </span>  <span class="Comment"># initialize</span>
-<span id="L815" class="LineNr"> 815 </span>  assume-resources [
-<span id="L816" class="LineNr"> 816 </span>  ]
-<span id="L817" class="LineNr"> 817 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 2, 2]</span>
-<span id="L818" class="LineNr"> 818 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L819" class="LineNr"> 819 </span>  assume-console [
-<span id="L820" class="LineNr"> 820 </span>  <span class="Conceal">¦</span> <span class="Comment"># create a sandbox</span>
-<span id="L821" class="LineNr"> 821 </span>  <span class="Conceal">¦</span> press F4
-<span id="L822" class="LineNr"> 822 </span>  ]
-<span id="L823" class="LineNr"> 823 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L824" class="LineNr"> 824 </span>  screen-should-contain [
-<span id="L825" class="LineNr"> 825 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L826" class="LineNr"> 826 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L827" class="LineNr"> 827 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L828" class="LineNr"> 828 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L829" class="LineNr"> 829 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L830" class="LineNr"> 830 </span>  ]
-<span id="L831" class="LineNr"> 831 </span>  <span class="Comment"># switch to sandbox window and hit 'page-down'</span>
-<span id="L832" class="LineNr"> 832 </span>  assume-console [
-<span id="L833" class="LineNr"> 833 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L834" class="LineNr"> 834 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L835" class="LineNr"> 835 </span>  ]
-<span id="L836" class="LineNr"> 836 </span>  run [
-<span id="L837" class="LineNr"> 837 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L838" class="LineNr"> 838 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L839" class="LineNr"> 839 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L840" class="LineNr"> 840 </span>  ]
-<span id="L841" class="LineNr"> 841 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
-<span id="L842" class="LineNr"> 842 </span>  <span class="Comment"># cursor moves to first sandbox</span>
-<span id="L843" class="LineNr"> 843 </span>  screen-should-contain [
-<span id="L844" class="LineNr"> 844 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L845" class="LineNr"> 845 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L846" class="LineNr"> 846 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
-<span id="L847" class="LineNr"> 847 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L848" class="LineNr"> 848 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L849" class="LineNr"> 849 </span>  ]
-<span id="L850" class="LineNr"> 850 </span>  <span class="Comment"># hit 'page-up'</span>
-<span id="L851" class="LineNr"> 851 </span>  assume-console [
-<span id="L852" class="LineNr"> 852 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
-<span id="L853" class="LineNr"> 853 </span>  ]
-<span id="L854" class="LineNr"> 854 </span>  run [
-<span id="L855" class="LineNr"> 855 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L856" class="LineNr"> 856 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L857" class="LineNr"> 857 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L858" class="LineNr"> 858 </span>  ]
-<span id="L859" class="LineNr"> 859 </span>  <span class="Comment"># sandbox editor displays again, cursor is in editor</span>
-<span id="L860" class="LineNr"> 860 </span>  screen-should-contain [
-<span id="L861" class="LineNr"> 861 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L862" class="LineNr"> 862 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
-<span id="L863" class="LineNr"> 863 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L864" class="LineNr"> 864 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L865" class="LineNr"> 865 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L866" class="LineNr"> 866 </span>  ]
-<span id="L867" class="LineNr"> 867 </span>]
-<span id="L868" class="LineNr"> 868 </span>
-<span id="L869" class="LineNr"> 869 </span><span class="Comment"># page-down on sandbox side updates render-from to scroll sandboxes</span>
-<span id="L870" class="LineNr"> 870 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
-<span id="L871" class="LineNr"> 871 </span>  <span class="Delimiter">{</span>
-<span id="L872" class="LineNr"> 872 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
-<span id="L873" class="LineNr"> 873 </span>  <span class="Conceal">¦</span> page-down?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65518/page-down</span>
-<span id="L874" class="LineNr"> 874 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-down?
-<span id="L875" class="LineNr"> 875 </span>  <span class="Conceal">¦</span> sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L876" class="LineNr"> 876 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox
-<span id="L877" class="LineNr"> 877 </span>  <span class="Conceal">¦</span> <span class="Comment"># slide down if possible</span>
-<span id="L878" class="LineNr"> 878 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
-<span id="L879" class="LineNr"> 879 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
-<span id="L880" class="LineNr"> 880 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> number-of-sandboxes:num <span class="Special">&lt;-</span> get *env, <span class="Constant">number-of-sandboxes:offset</span>
-<span id="L881" class="LineNr"> 881 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> max:num <span class="Special">&lt;-</span> subtract number-of-sandboxes,<span class="Constant"> 1</span>
-<span id="L882" class="LineNr"> 882 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-end?:bool <span class="Special">&lt;-</span> greater-or-equal render-from, max
-<span id="L883" class="LineNr"> 883 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">jump-if</span> at-end?, <span class="Constant">+finish-event</span>  <span class="Comment"># render nothing</span>
-<span id="L884" class="LineNr"> 884 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> render-from <span class="Special">&lt;-</span> add render-from,<span class="Constant"> 1</span>
-<span id="L885" class="LineNr"> 885 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>, render-from
-<span id="L886" class="LineNr"> 886 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
-<span id="L887" class="LineNr"> 887 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L888" class="LineNr"> 888 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L889" class="LineNr"> 889 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L890" class="LineNr"> 890 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+finish-event</span>
-<span id="L891" class="LineNr"> 891 </span>  <span class="Delimiter">}</span>
-<span id="L892" class="LineNr"> 892 </span>]
-<span id="L893" class="LineNr"> 893 </span>
-<span id="L894" class="LineNr"> 894 </span><span class="Comment"># update-cursor takes render-from into account</span>
-<span id="L895" class="LineNr"> 895 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L514'>&lt;update-cursor-special-cases&gt;</a></span> [
-<span id="L896" class="LineNr"> 896 </span>  <span class="Delimiter">{</span>
-<span id="L897" class="LineNr"> 897 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
-<span id="L898" class="LineNr"> 898 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
-<span id="L899" class="LineNr"> 899 </span>  <span class="Conceal">¦</span> scrolling?:bool <span class="Special">&lt;-</span> greater-or-equal render-from,<span class="Constant"> 0</span>
-<span id="L900" class="LineNr"> 900 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> scrolling?
-<span id="L901" class="LineNr"> 901 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
-<span id="L902" class="LineNr"> 902 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">2/row</span>, cursor-column  <span class="Comment"># highlighted sandbox will always start at row 2</span>
-<span id="L903" class="LineNr"> 903 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
-<span id="L904" class="LineNr"> 904 </span>  <span class="Delimiter">}</span>
-<span id="L905" class="LineNr"> 905 </span>]
-<span id="L906" class="LineNr"> 906 </span>
-<span id="L907" class="LineNr"> 907 </span><span class="Comment"># 'page-up' on sandbox side is like 'page-down': updates render-from when necessary</span>
-<span id="L908" class="LineNr"> 908 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
-<span id="L909" class="LineNr"> 909 </span>  <span class="Delimiter">{</span>
-<span id="L910" class="LineNr"> 910 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
-<span id="L911" class="LineNr"> 911 </span>  <span class="Conceal">¦</span> page-up?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65519/page-up</span>
-<span id="L912" class="LineNr"> 912 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-up?
-<span id="L913" class="LineNr"> 913 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
-<span id="L914" class="LineNr"> 914 </span>  <span class="Conceal">¦</span> at-beginning?:bool <span class="Special">&lt;-</span> equal render-from,<span class="Constant"> -1</span>
-<span id="L915" class="LineNr"> 915 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> at-beginning?
-<span id="L916" class="LineNr"> 916 </span>  <span class="Conceal">¦</span> render-from <span class="Special">&lt;-</span> subtract render-from,<span class="Constant"> 1</span>
-<span id="L917" class="LineNr"> 917 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>, render-from
-<span id="L918" class="LineNr"> 918 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L919" class="LineNr"> 919 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L920" class="LineNr"> 920 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
-<span id="L921" class="LineNr"> 921 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+finish-event</span>
-<span id="L922" class="LineNr"> 922 </span>  <span class="Delimiter">}</span>
-<span id="L923" class="LineNr"> 923 </span>]
-<span id="L924" class="LineNr"> 924 </span>
-<span id="L925" class="LineNr"> 925 </span><span class="Comment"># sandbox belonging to 'env' whose next-sandbox is 'in'</span>
-<span id="L926" class="LineNr"> 926 </span><span class="Comment"># return 0 if there's no such sandbox, either because 'in' doesn't exist in 'env', or because it's the first sandbox</span>
-<span id="L927" class="LineNr"> 927 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L927'>previous-sandbox</a> env:&amp;:environment, in:&amp;:sandbox<span class="muRecipe"> -&gt; </span>out:&amp;:sandbox [
-<span id="L928" class="LineNr"> 928 </span>  <span class="Constant">local-scope</span>
-<span id="L929" class="LineNr"> 929 </span>  <span class="Constant">load-ingredients</span>
-<span id="L930" class="LineNr"> 930 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
-<span id="L931" class="LineNr"> 931 </span>  <span class="muControl">return-unless</span> curr, <span class="Constant">0/nil</span>
-<span id="L932" class="LineNr"> 932 </span>  <a href='../065duplex_list.mu.html#L29'>next</a>:&amp;:sandbox <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
-<span id="L933" class="LineNr"> 933 </span>  <span class="Delimiter">{</span>
-<span id="L934" class="LineNr"> 934 </span>  <span class="Conceal">¦</span> <span class="muControl">return-unless</span> <a href='../065duplex_list.mu.html#L29'>next</a>, <span class="Constant">0/nil</span>
-<span id="L935" class="LineNr"> 935 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal <a href='../065duplex_list.mu.html#L29'>next</a>, in
-<span id="L936" class="LineNr"> 936 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
-<span id="L937" class="LineNr"> 937 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L29'>next</a>
-<span id="L938" class="LineNr"> 938 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L29'>next</a> <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
-<span id="L939" class="LineNr"> 939 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
-<span id="L940" class="LineNr"> 940 </span>  <span class="Delimiter">}</span>
-<span id="L941" class="LineNr"> 941 </span>  <span class="muControl">return</span> curr
-<span id="L942" class="LineNr"> 942 </span>]
-<span id="L943" class="LineNr"> 943 </span>
-<span id="L944" class="LineNr"> 944 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-on-recipe-side [
-<span id="L945" class="LineNr"> 945 </span>  <span class="Constant">local-scope</span>
-<span id="L946" class="LineNr"> 946 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L947" class="LineNr"> 947 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L948" class="LineNr"> 948 </span>  <span class="Comment"># initialize sandbox side and create a sandbox</span>
-<span id="L949" class="LineNr"> 949 </span>  assume-resources [
-<span id="L950" class="LineNr"> 950 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
-<span id="L951" class="LineNr"> 951 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">||</span>  <span class="Comment"># file containing just a newline</span>
-<span id="L952" class="LineNr"> 952 </span>  <span class="Conceal">¦</span> ]
-<span id="L953" class="LineNr"> 953 </span>  ]
-<span id="L954" class="LineNr"> 954 </span>  <span class="Comment"># create a sandbox</span>
-<span id="L955" class="LineNr"> 955 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 2, 2]</span>
-<span id="L956" class="LineNr"> 956 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L957" class="LineNr"> 957 </span>  assume-console [
-<span id="L958" class="LineNr"> 958 </span>  <span class="Conceal">¦</span> press F4
-<span id="L959" class="LineNr"> 959 </span>  ]
-<span id="L960" class="LineNr"> 960 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L961" class="LineNr"> 961 </span>  <span class="Comment"># hit 'down' in recipe editor</span>
-<span id="L962" class="LineNr"> 962 </span>  assume-console [
-<span id="L963" class="LineNr"> 963 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L964" class="LineNr"> 964 </span>  ]
-<span id="L965" class="LineNr"> 965 </span>  run [
-<span id="L966" class="LineNr"> 966 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L967" class="LineNr"> 967 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L968" class="LineNr"> 968 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L969" class="LineNr"> 969 </span>  ]
-<span id="L970" class="LineNr"> 970 </span>  <span class="Comment"># cursor doesn't move when the end is already on-screen</span>
-<span id="L971" class="LineNr"> 971 </span>  screen-should-contain [
-<span id="L972" class="LineNr"> 972 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L973" class="LineNr"> 973 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣                                                 ╎                                                 .</span>
-<span id="L974" class="LineNr"> 974 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L975" class="LineNr"> 975 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L976" class="LineNr"> 976 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L977" class="LineNr"> 977 </span>  ]
-<span id="L978" class="LineNr"> 978 </span>]
-<span id="L979" class="LineNr"> 979 </span>
-<span id="L980" class="LineNr"> 980 </span><span class="muScenario">scenario</span> scrolling-through-multiple-sandboxes [
-<span id="L981" class="LineNr"> 981 </span>  <span class="Constant">local-scope</span>
-<span id="L982" class="LineNr"> 982 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L983" class="LineNr"> 983 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L984" class="LineNr"> 984 </span>  <span class="Comment"># initialize environment</span>
-<span id="L985" class="LineNr"> 985 </span>  assume-resources [
-<span id="L986" class="LineNr"> 986 </span>  ]
-<span id="L987" class="LineNr"> 987 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L988" class="LineNr"> 988 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L989" class="LineNr"> 989 </span>  <span class="Comment"># create 2 sandboxes</span>
-<span id="L990" class="LineNr"> 990 </span>  assume-console [
-<span id="L991" class="LineNr"> 991 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L992" class="LineNr"> 992 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
-<span id="L993" class="LineNr"> 993 </span>  <span class="Conceal">¦</span> press F4
-<span id="L994" class="LineNr"> 994 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L810" class="LineNr"> 810 </span><span class="Comment"># scrolling through sandboxes</span>
+<span id="L811" class="LineNr"> 811 </span>
+<span id="L812" class="LineNr"> 812 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-of-sandbox-editor [
+<span id="L813" class="LineNr"> 813 </span>  <span class="Constant">local-scope</span>
+<span id="L814" class="LineNr"> 814 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L815" class="LineNr"> 815 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L816" class="LineNr"> 816 </span>  <span class="Comment"># initialize</span>
+<span id="L817" class="LineNr"> 817 </span>  assume-resources [
+<span id="L818" class="LineNr"> 818 </span>  ]
+<span id="L819" class="LineNr"> 819 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 2, 2]</span>
+<span id="L820" class="LineNr"> 820 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L821" class="LineNr"> 821 </span>  assume-console [
+<span id="L822" class="LineNr"> 822 </span>  <span class="Conceal">¦</span> <span class="Comment"># create a sandbox</span>
+<span id="L823" class="LineNr"> 823 </span>  <span class="Conceal">¦</span> press F4
+<span id="L824" class="LineNr"> 824 </span>  ]
+<span id="L825" class="LineNr"> 825 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L826" class="LineNr"> 826 </span>  screen-should-contain [
+<span id="L827" class="LineNr"> 827 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L828" class="LineNr"> 828 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L829" class="LineNr"> 829 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L830" class="LineNr"> 830 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L831" class="LineNr"> 831 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L832" class="LineNr"> 832 </span>  ]
+<span id="L833" class="LineNr"> 833 </span>  <span class="Comment"># switch to sandbox window and hit 'page-down'</span>
+<span id="L834" class="LineNr"> 834 </span>  assume-console [
+<span id="L835" class="LineNr"> 835 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L836" class="LineNr"> 836 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L837" class="LineNr"> 837 </span>  ]
+<span id="L838" class="LineNr"> 838 </span>  run [
+<span id="L839" class="LineNr"> 839 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L840" class="LineNr"> 840 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L841" class="LineNr"> 841 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L842" class="LineNr"> 842 </span>  ]
+<span id="L843" class="LineNr"> 843 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+<span id="L844" class="LineNr"> 844 </span>  <span class="Comment"># cursor moves to first sandbox</span>
+<span id="L845" class="LineNr"> 845 </span>  screen-should-contain [
+<span id="L846" class="LineNr"> 846 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L847" class="LineNr"> 847 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L848" class="LineNr"> 848 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
+<span id="L849" class="LineNr"> 849 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L850" class="LineNr"> 850 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L851" class="LineNr"> 851 </span>  ]
+<span id="L852" class="LineNr"> 852 </span>  <span class="Comment"># hit 'page-up'</span>
+<span id="L853" class="LineNr"> 853 </span>  assume-console [
+<span id="L854" class="LineNr"> 854 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L855" class="LineNr"> 855 </span>  ]
+<span id="L856" class="LineNr"> 856 </span>  run [
+<span id="L857" class="LineNr"> 857 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L858" class="LineNr"> 858 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L859" class="LineNr"> 859 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L860" class="LineNr"> 860 </span>  ]
+<span id="L861" class="LineNr"> 861 </span>  <span class="Comment"># sandbox editor displays again, cursor is in editor</span>
+<span id="L862" class="LineNr"> 862 </span>  screen-should-contain [
+<span id="L863" class="LineNr"> 863 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L864" class="LineNr"> 864 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
+<span id="L865" class="LineNr"> 865 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L866" class="LineNr"> 866 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L867" class="LineNr"> 867 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L868" class="LineNr"> 868 </span>  ]
+<span id="L869" class="LineNr"> 869 </span>]
+<span id="L870" class="LineNr"> 870 </span>
+<span id="L871" class="LineNr"> 871 </span><span class="Comment"># page-down on sandbox side updates render-from to scroll sandboxes</span>
+<span id="L872" class="LineNr"> 872 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
+<span id="L873" class="LineNr"> 873 </span>  <span class="Delimiter">{</span>
+<span id="L874" class="LineNr"> 874 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
+<span id="L875" class="LineNr"> 875 </span>  <span class="Conceal">¦</span> page-down?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65518/page-down</span>
+<span id="L876" class="LineNr"> 876 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-down?
+<span id="L877" class="LineNr"> 877 </span>  <span class="Conceal">¦</span> sandbox:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L878" class="LineNr"> 878 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox
+<span id="L879" class="LineNr"> 879 </span>  <span class="Conceal">¦</span> <span class="Comment"># slide down if possible</span>
+<span id="L880" class="LineNr"> 880 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
+<span id="L881" class="LineNr"> 881 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
+<span id="L882" class="LineNr"> 882 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> number-of-sandboxes:num <span class="Special">&lt;-</span> get *env, <span class="Constant">number-of-sandboxes:offset</span>
+<span id="L883" class="LineNr"> 883 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> max:num <span class="Special">&lt;-</span> subtract number-of-sandboxes,<span class="Constant"> 1</span>
+<span id="L884" class="LineNr"> 884 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> at-end?:bool <span class="Special">&lt;-</span> greater-or-equal render-from, max
+<span id="L885" class="LineNr"> 885 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">jump-if</span> at-end?, <span class="Constant">+finish-event</span>  <span class="Comment"># render nothing</span>
+<span id="L886" class="LineNr"> 886 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> render-from <span class="Special">&lt;-</span> add render-from,<span class="Constant"> 1</span>
+<span id="L887" class="LineNr"> 887 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>, render-from
+<span id="L888" class="LineNr"> 888 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
+<span id="L889" class="LineNr"> 889 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L890" class="LineNr"> 890 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L891" class="LineNr"> 891 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L892" class="LineNr"> 892 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+finish-event</span>
+<span id="L893" class="LineNr"> 893 </span>  <span class="Delimiter">}</span>
+<span id="L894" class="LineNr"> 894 </span>]
+<span id="L895" class="LineNr"> 895 </span>
+<span id="L896" class="LineNr"> 896 </span><span class="Comment"># update-cursor takes render-from into account</span>
+<span id="L897" class="LineNr"> 897 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L514'>&lt;update-cursor-special-cases&gt;</a></span> [
+<span id="L898" class="LineNr"> 898 </span>  <span class="Delimiter">{</span>
+<span id="L899" class="LineNr"> 899 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
+<span id="L900" class="LineNr"> 900 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
+<span id="L901" class="LineNr"> 901 </span>  <span class="Conceal">¦</span> scrolling?:bool <span class="Special">&lt;-</span> greater-or-equal render-from,<span class="Constant"> 0</span>
+<span id="L902" class="LineNr"> 902 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> scrolling?
+<span id="L903" class="LineNr"> 903 </span>  <span class="Conceal">¦</span> cursor-column:num <span class="Special">&lt;-</span> get *current-sandbox, <span class="Constant">left:offset</span>
+<span id="L904" class="LineNr"> 904 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='../081print.mu.html#L442'>move-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">2/row</span>, cursor-column  <span class="Comment"># highlighted sandbox will always start at row 2</span>
+<span id="L905" class="LineNr"> 905 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
+<span id="L906" class="LineNr"> 906 </span>  <span class="Delimiter">}</span>
+<span id="L907" class="LineNr"> 907 </span>]
+<span id="L908" class="LineNr"> 908 </span>
+<span id="L909" class="LineNr"> 909 </span><span class="Comment"># 'page-up' on sandbox side is like 'page-down': updates render-from when necessary</span>
+<span id="L910" class="LineNr"> 910 </span><span class="muRecipe">after</span> <span class="Constant"><a href='004-programming-environment.mu.html#L61'>&lt;global-keypress&gt;</a></span> [
+<span id="L911" class="LineNr"> 911 </span>  <span class="Delimiter">{</span>
+<span id="L912" class="LineNr"> 912 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-in-focus?
+<span id="L913" class="LineNr"> 913 </span>  <span class="Conceal">¦</span> page-up?:bool <span class="Special">&lt;-</span> equal k, <span class="Constant">65519/page-up</span>
+<span id="L914" class="LineNr"> 914 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> page-up?
+<span id="L915" class="LineNr"> 915 </span>  <span class="Conceal">¦</span> render-from:num <span class="Special">&lt;-</span> get *env, <span class="Constant">render-from:offset</span>
+<span id="L916" class="LineNr"> 916 </span>  <span class="Conceal">¦</span> at-beginning?:bool <span class="Special">&lt;-</span> equal render-from,<span class="Constant"> -1</span>
+<span id="L917" class="LineNr"> 917 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> at-beginning?
+<span id="L918" class="LineNr"> 918 </span>  <span class="Conceal">¦</span> render-from <span class="Special">&lt;-</span> subtract render-from,<span class="Constant"> 1</span>
+<span id="L919" class="LineNr"> 919 </span>  <span class="Conceal">¦</span> *env <span class="Special">&lt;-</span> put *env, <span class="Constant">render-from:offset</span>, render-from
+<span id="L920" class="LineNr"> 920 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L921" class="LineNr"> 921 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L922" class="LineNr"> 922 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L631'>show-screen</a> <a href='../081print.mu.html#L4'>screen</a>
+<span id="L923" class="LineNr"> 923 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+finish-event</span>
+<span id="L924" class="LineNr"> 924 </span>  <span class="Delimiter">}</span>
+<span id="L925" class="LineNr"> 925 </span>]
+<span id="L926" class="LineNr"> 926 </span>
+<span id="L927" class="LineNr"> 927 </span><span class="Comment"># sandbox belonging to 'env' whose next-sandbox is 'in'</span>
+<span id="L928" class="LineNr"> 928 </span><span class="Comment"># return 0 if there's no such sandbox, either because 'in' doesn't exist in 'env', or because it's the first sandbox</span>
+<span id="L929" class="LineNr"> 929 </span><span class="muRecipe">def</span> <a href='005-sandbox.mu.html#L929'>previous-sandbox</a> env:&amp;:environment, in:&amp;:sandbox<span class="muRecipe"> -&gt; </span>out:&amp;:sandbox [
+<span id="L930" class="LineNr"> 930 </span>  <span class="Constant">local-scope</span>
+<span id="L931" class="LineNr"> 931 </span>  <span class="Constant">load-ingredients</span>
+<span id="L932" class="LineNr"> 932 </span>  curr:&amp;:sandbox <span class="Special">&lt;-</span> get *env, <span class="Constant">sandbox:offset</span>
+<span id="L933" class="LineNr"> 933 </span>  <span class="muControl">return-unless</span> curr, <span class="Constant">0/nil</span>
+<span id="L934" class="LineNr"> 934 </span>  <a href='../065duplex_list.mu.html#L29'>next</a>:&amp;:sandbox <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
+<span id="L935" class="LineNr"> 935 </span>  <span class="Delimiter">{</span>
+<span id="L936" class="LineNr"> 936 </span>  <span class="Conceal">¦</span> <span class="muControl">return-unless</span> <a href='../065duplex_list.mu.html#L29'>next</a>, <span class="Constant">0/nil</span>
+<span id="L937" class="LineNr"> 937 </span>  <span class="Conceal">¦</span> found?:bool <span class="Special">&lt;-</span> equal <a href='../065duplex_list.mu.html#L29'>next</a>, in
+<span id="L938" class="LineNr"> 938 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> found?
+<span id="L939" class="LineNr"> 939 </span>  <span class="Conceal">¦</span> curr <span class="Special">&lt;-</span> copy <a href='../065duplex_list.mu.html#L29'>next</a>
+<span id="L940" class="LineNr"> 940 </span>  <span class="Conceal">¦</span> <a href='../065duplex_list.mu.html#L29'>next</a> <span class="Special">&lt;-</span> get *curr, <span class="Constant">next-sandbox:offset</span>
+<span id="L941" class="LineNr"> 941 </span>  <span class="Conceal">¦</span> <span class="muControl">loop</span>
+<span id="L942" class="LineNr"> 942 </span>  <span class="Delimiter">}</span>
+<span id="L943" class="LineNr"> 943 </span>  <span class="muControl">return</span> curr
+<span id="L944" class="LineNr"> 944 </span>]
+<span id="L945" class="LineNr"> 945 </span>
+<span id="L946" class="LineNr"> 946 </span><span class="muScenario">scenario</span> scrolling-down-past-bottom-on-recipe-side [
+<span id="L947" class="LineNr"> 947 </span>  <span class="Constant">local-scope</span>
+<span id="L948" class="LineNr"> 948 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L949" class="LineNr"> 949 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L950" class="LineNr"> 950 </span>  <span class="Comment"># initialize sandbox side and create a sandbox</span>
+<span id="L951" class="LineNr"> 951 </span>  assume-resources [
+<span id="L952" class="LineNr"> 952 </span>  <span class="Conceal">¦</span> <span class="Constant">[lesson/recipes.mu]</span> <span class="Special">&lt;-</span> [
+<span id="L953" class="LineNr"> 953 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="Constant">||</span>  <span class="Comment"># file containing just a newline</span>
+<span id="L954" class="LineNr"> 954 </span>  <span class="Conceal">¦</span> ]
+<span id="L955" class="LineNr"> 955 </span>  ]
+<span id="L956" class="LineNr"> 956 </span>  <span class="Comment"># create a sandbox</span>
+<span id="L957" class="LineNr"> 957 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[add 2, 2]</span>
+<span id="L958" class="LineNr"> 958 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L959" class="LineNr"> 959 </span>  assume-console [
+<span id="L960" class="LineNr"> 960 </span>  <span class="Conceal">¦</span> press F4
+<span id="L961" class="LineNr"> 961 </span>  ]
+<span id="L962" class="LineNr"> 962 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L963" class="LineNr"> 963 </span>  <span class="Comment"># hit 'down' in recipe editor</span>
+<span id="L964" class="LineNr"> 964 </span>  assume-console [
+<span id="L965" class="LineNr"> 965 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L966" class="LineNr"> 966 </span>  ]
+<span id="L967" class="LineNr"> 967 </span>  run [
+<span id="L968" class="LineNr"> 968 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L969" class="LineNr"> 969 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L970" class="LineNr"> 970 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L971" class="LineNr"> 971 </span>  ]
+<span id="L972" class="LineNr"> 972 </span>  <span class="Comment"># cursor doesn't move when the end is already on-screen</span>
+<span id="L973" class="LineNr"> 973 </span>  screen-should-contain [
+<span id="L974" class="LineNr"> 974 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L975" class="LineNr"> 975 </span>  <span class="Conceal">¦</span><span class="Constant"> .␣                                                 ╎                                                 .</span>
+<span id="L976" class="LineNr"> 976 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L977" class="LineNr"> 977 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L978" class="LineNr"> 978 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L979" class="LineNr"> 979 </span>  ]
+<span id="L980" class="LineNr"> 980 </span>]
+<span id="L981" class="LineNr"> 981 </span>
+<span id="L982" class="LineNr"> 982 </span><span class="muScenario">scenario</span> scrolling-through-multiple-sandboxes [
+<span id="L983" class="LineNr"> 983 </span>  <span class="Constant">local-scope</span>
+<span id="L984" class="LineNr"> 984 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L985" class="LineNr"> 985 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L986" class="LineNr"> 986 </span>  <span class="Comment"># initialize environment</span>
+<span id="L987" class="LineNr"> 987 </span>  assume-resources [
+<span id="L988" class="LineNr"> 988 </span>  ]
+<span id="L989" class="LineNr"> 989 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L990" class="LineNr"> 990 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L991" class="LineNr"> 991 </span>  <span class="Comment"># create 2 sandboxes</span>
+<span id="L992" class="LineNr"> 992 </span>  assume-console [
+<span id="L993" class="LineNr"> 993 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L994" class="LineNr"> 994 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 2, 2]</span>
 <span id="L995" class="LineNr"> 995 </span>  <span class="Conceal">¦</span> press F4
-<span id="L996" class="LineNr"> 996 </span>  ]
-<span id="L997" class="LineNr"> 997 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L998" class="LineNr"> 998 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L999" class="LineNr"> 999 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1000" class="LineNr">1000 </span>  screen-should-contain [
-<span id="L1001" class="LineNr">1001 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1002" class="LineNr">1002 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
-<span id="L1003" class="LineNr">1003 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1004" class="LineNr">1004 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1005" class="LineNr">1005 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1006" class="LineNr">1006 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1007" class="LineNr">1007 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1008" class="LineNr">1008 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1009" class="LineNr">1009 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1010" class="LineNr">1010 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1011" class="LineNr">1011 </span>  ]
-<span id="L1012" class="LineNr">1012 </span>  <span class="Comment"># hit 'page-down'</span>
-<span id="L1013" class="LineNr">1013 </span>  assume-console [
-<span id="L1014" class="LineNr">1014 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L1015" class="LineNr">1015 </span>  ]
-<span id="L1016" class="LineNr">1016 </span>  run [
-<span id="L1017" class="LineNr">1017 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1018" class="LineNr">1018 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1019" class="LineNr">1019 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1020" class="LineNr">1020 </span>  ]
-<span id="L1021" class="LineNr">1021 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
-<span id="L1022" class="LineNr">1022 </span>  <span class="Comment"># cursor moves to first sandbox</span>
-<span id="L1023" class="LineNr">1023 </span>  screen-should-contain [
-<span id="L1024" class="LineNr">1024 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1025" class="LineNr">1025 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1026" class="LineNr">1026 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
-<span id="L1027" class="LineNr">1027 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1028" class="LineNr">1028 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1029" class="LineNr">1029 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1030" class="LineNr">1030 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1031" class="LineNr">1031 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1032" class="LineNr">1032 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1033" class="LineNr">1033 </span>  ]
-<span id="L1034" class="LineNr">1034 </span>  <span class="Comment"># hit 'page-down' again</span>
-<span id="L1035" class="LineNr">1035 </span>  assume-console [
-<span id="L1036" class="LineNr">1036 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L1037" class="LineNr">1037 </span>  ]
-<span id="L1038" class="LineNr">1038 </span>  run [
-<span id="L1039" class="LineNr">1039 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1040" class="LineNr">1040 </span>  ]
-<span id="L1041" class="LineNr">1041 </span>  <span class="Comment"># just second sandbox displayed</span>
-<span id="L1042" class="LineNr">1042 </span>  screen-should-contain [
-<span id="L1043" class="LineNr">1043 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1044" class="LineNr">1044 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1045" class="LineNr">1045 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
-<span id="L1046" class="LineNr">1046 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1047" class="LineNr">1047 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1048" class="LineNr">1048 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1049" class="LineNr">1049 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1050" class="LineNr">1050 </span>  ]
-<span id="L1051" class="LineNr">1051 </span>  <span class="Comment"># hit 'page-down' again</span>
-<span id="L1052" class="LineNr">1052 </span>  assume-console [
-<span id="L1053" class="LineNr">1053 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L1054" class="LineNr">1054 </span>  ]
-<span id="L1055" class="LineNr">1055 </span>  run [
-<span id="L1056" class="LineNr">1056 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1057" class="LineNr">1057 </span>  ]
-<span id="L1058" class="LineNr">1058 </span>  <span class="Comment"># no change</span>
-<span id="L1059" class="LineNr">1059 </span>  screen-should-contain [
-<span id="L1060" class="LineNr">1060 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1061" class="LineNr">1061 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1062" class="LineNr">1062 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
-<span id="L1063" class="LineNr">1063 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1064" class="LineNr">1064 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1065" class="LineNr">1065 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1066" class="LineNr">1066 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1067" class="LineNr">1067 </span>  ]
-<span id="L1068" class="LineNr">1068 </span>  <span class="Comment"># hit 'page-up'</span>
-<span id="L1069" class="LineNr">1069 </span>  assume-console [
-<span id="L1070" class="LineNr">1070 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
-<span id="L1071" class="LineNr">1071 </span>  ]
-<span id="L1072" class="LineNr">1072 </span>  run [
-<span id="L1073" class="LineNr">1073 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1074" class="LineNr">1074 </span>  ]
-<span id="L1075" class="LineNr">1075 </span>  <span class="Comment"># back to displaying both sandboxes without editor</span>
-<span id="L1076" class="LineNr">1076 </span>  screen-should-contain [
-<span id="L1077" class="LineNr">1077 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1078" class="LineNr">1078 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1079" class="LineNr">1079 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L1080" class="LineNr">1080 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1081" class="LineNr">1081 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1082" class="LineNr">1082 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1083" class="LineNr">1083 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1084" class="LineNr">1084 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1085" class="LineNr">1085 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1086" class="LineNr">1086 </span>  ]
-<span id="L1087" class="LineNr">1087 </span>  <span class="Comment"># hit 'page-up' again</span>
-<span id="L1088" class="LineNr">1088 </span>  assume-console [
-<span id="L1089" class="LineNr">1089 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
-<span id="L1090" class="LineNr">1090 </span>  ]
-<span id="L1091" class="LineNr">1091 </span>  run [
-<span id="L1092" class="LineNr">1092 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1093" class="LineNr">1093 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1094" class="LineNr">1094 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1095" class="LineNr">1095 </span>  ]
-<span id="L1096" class="LineNr">1096 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
-<span id="L1097" class="LineNr">1097 </span>  screen-should-contain [
-<span id="L1098" class="LineNr">1098 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1099" class="LineNr">1099 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
-<span id="L1100" class="LineNr">1100 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1101" class="LineNr">1101 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1102" class="LineNr">1102 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1103" class="LineNr">1103 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1104" class="LineNr">1104 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1105" class="LineNr">1105 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1106" class="LineNr">1106 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1107" class="LineNr">1107 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1108" class="LineNr">1108 </span>  ]
-<span id="L1109" class="LineNr">1109 </span>  <span class="Comment"># hit 'page-up' again</span>
-<span id="L1110" class="LineNr">1110 </span>  assume-console [
-<span id="L1111" class="LineNr">1111 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
-<span id="L1112" class="LineNr">1112 </span>  ]
-<span id="L1113" class="LineNr">1113 </span>  run [
-<span id="L1114" class="LineNr">1114 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1115" class="LineNr">1115 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
-<span id="L1116" class="LineNr">1116 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
-<span id="L1117" class="LineNr">1117 </span>  ]
-<span id="L1118" class="LineNr">1118 </span>  <span class="Comment"># no change</span>
-<span id="L1119" class="LineNr">1119 </span>  screen-should-contain [
-<span id="L1120" class="LineNr">1120 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1121" class="LineNr">1121 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
-<span id="L1122" class="LineNr">1122 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1123" class="LineNr">1123 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1124" class="LineNr">1124 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1125" class="LineNr">1125 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1126" class="LineNr">1126 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1127" class="LineNr">1127 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
-<span id="L1128" class="LineNr">1128 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
-<span id="L1129" class="LineNr">1129 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
-<span id="L1130" class="LineNr">1130 </span>  ]
-<span id="L1131" class="LineNr">1131 </span>]
-<span id="L1132" class="LineNr">1132 </span>
-<span id="L1133" class="LineNr">1133 </span><span class="muScenario">scenario</span> scrolling-manages-sandbox-index-correctly [
-<span id="L1134" class="LineNr">1134 </span>  <span class="Constant">local-scope</span>
-<span id="L1135" class="LineNr">1135 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
-<span id="L1136" class="LineNr">1136 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
-<span id="L1137" class="LineNr">1137 </span>  <span class="Comment"># initialize environment</span>
-<span id="L1138" class="LineNr">1138 </span>  assume-resources [
-<span id="L1139" class="LineNr">1139 </span>  ]
-<span id="L1140" class="LineNr">1140 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
-<span id="L1141" class="LineNr">1141 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
-<span id="L1142" class="LineNr">1142 </span>  <span class="Comment"># create a sandbox</span>
-<span id="L1143" class="LineNr">1143 </span>  assume-console [
-<span id="L1144" class="LineNr">1144 </span>  <span class="Conceal">¦</span> press ctrl-n
-<span id="L1145" class="LineNr">1145 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
-<span id="L1146" class="LineNr">1146 </span>  <span class="Conceal">¦</span> press F4
-<span id="L1147" class="LineNr">1147 </span>  ]
-<span id="L1148" class="LineNr">1148 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1149" class="LineNr">1149 </span>  screen-should-contain [
-<span id="L1150" class="LineNr">1150 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1151" class="LineNr">1151 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1152" class="LineNr">1152 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1153" class="LineNr">1153 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1154" class="LineNr">1154 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1155" class="LineNr">1155 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1156" class="LineNr">1156 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1157" class="LineNr">1157 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1158" class="LineNr">1158 </span>  ]
-<span id="L1159" class="LineNr">1159 </span>  <span class="Comment"># hit 'page-down' and 'page-up' a couple of times. sandbox index should be stable</span>
-<span id="L1160" class="LineNr">1160 </span>  assume-console [
-<span id="L1161" class="LineNr">1161 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L1162" class="LineNr">1162 </span>  ]
-<span id="L1163" class="LineNr">1163 </span>  run [
-<span id="L1164" class="LineNr">1164 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1165" class="LineNr">1165 </span>  ]
-<span id="L1166" class="LineNr">1166 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
-<span id="L1167" class="LineNr">1167 </span>  <span class="Comment"># cursor moves to first sandbox</span>
-<span id="L1168" class="LineNr">1168 </span>  screen-should-contain [
-<span id="L1169" class="LineNr">1169 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1170" class="LineNr">1170 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1171" class="LineNr">1171 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L1172" class="LineNr">1172 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1173" class="LineNr">1173 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1174" class="LineNr">1174 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1175" class="LineNr">1175 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1176" class="LineNr">1176 </span>  ]
-<span id="L1177" class="LineNr">1177 </span>  <span class="Comment"># hit 'page-up' again</span>
-<span id="L1178" class="LineNr">1178 </span>  assume-console [
-<span id="L1179" class="LineNr">1179 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
-<span id="L1180" class="LineNr">1180 </span>  ]
-<span id="L1181" class="LineNr">1181 </span>  run [
-<span id="L1182" class="LineNr">1182 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1183" class="LineNr">1183 </span>  ]
-<span id="L1184" class="LineNr">1184 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
-<span id="L1185" class="LineNr">1185 </span>  screen-should-contain [
-<span id="L1186" class="LineNr">1186 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1187" class="LineNr">1187 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1188" class="LineNr">1188 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
-<span id="L1189" class="LineNr">1189 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
-<span id="L1190" class="LineNr">1190 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1191" class="LineNr">1191 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1192" class="LineNr">1192 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1193" class="LineNr">1193 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1194" class="LineNr">1194 </span>  ]
-<span id="L1195" class="LineNr">1195 </span>  <span class="Comment"># hit 'page-down'</span>
-<span id="L1196" class="LineNr">1196 </span>  assume-console [
-<span id="L1197" class="LineNr">1197 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
-<span id="L1198" class="LineNr">1198 </span>  ]
-<span id="L1199" class="LineNr">1199 </span>  run [
-<span id="L1200" class="LineNr">1200 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
-<span id="L1201" class="LineNr">1201 </span>  ]
-<span id="L1202" class="LineNr">1202 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
-<span id="L1203" class="LineNr">1203 </span>  <span class="Comment"># cursor moves to first sandbox</span>
-<span id="L1204" class="LineNr">1204 </span>  screen-should-contain [
-<span id="L1205" class="LineNr">1205 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
-<span id="L1206" class="LineNr">1206 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1207" class="LineNr">1207 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
-<span id="L1208" class="LineNr">1208 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
-<span id="L1209" class="LineNr">1209 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
-<span id="L1210" class="LineNr">1210 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
-<span id="L1211" class="LineNr">1211 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
-<span id="L1212" class="LineNr">1212 </span>  ]
-<span id="L1213" class="LineNr">1213 </span>]
+<span id="L996" class="LineNr"> 996 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L997" class="LineNr"> 997 </span>  <span class="Conceal">¦</span> press F4
+<span id="L998" class="LineNr"> 998 </span>  ]
+<span id="L999" class="LineNr"> 999 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1000" class="LineNr">1000 </span>  cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1001" class="LineNr">1001 </span>  print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1002" class="LineNr">1002 </span>  screen-should-contain [
+<span id="L1003" class="LineNr">1003 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1004" class="LineNr">1004 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
+<span id="L1005" class="LineNr">1005 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1006" class="LineNr">1006 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1007" class="LineNr">1007 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1008" class="LineNr">1008 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1009" class="LineNr">1009 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1010" class="LineNr">1010 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1011" class="LineNr">1011 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1012" class="LineNr">1012 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1013" class="LineNr">1013 </span>  ]
+<span id="L1014" class="LineNr">1014 </span>  <span class="Comment"># hit 'page-down'</span>
+<span id="L1015" class="LineNr">1015 </span>  assume-console [
+<span id="L1016" class="LineNr">1016 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1017" class="LineNr">1017 </span>  ]
+<span id="L1018" class="LineNr">1018 </span>  run [
+<span id="L1019" class="LineNr">1019 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1020" class="LineNr">1020 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1021" class="LineNr">1021 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1022" class="LineNr">1022 </span>  ]
+<span id="L1023" class="LineNr">1023 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+<span id="L1024" class="LineNr">1024 </span>  <span class="Comment"># cursor moves to first sandbox</span>
+<span id="L1025" class="LineNr">1025 </span>  screen-should-contain [
+<span id="L1026" class="LineNr">1026 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1027" class="LineNr">1027 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1028" class="LineNr">1028 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎␣   edit          copy            delete         .</span>
+<span id="L1029" class="LineNr">1029 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1030" class="LineNr">1030 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1031" class="LineNr">1031 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1032" class="LineNr">1032 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1033" class="LineNr">1033 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1034" class="LineNr">1034 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1035" class="LineNr">1035 </span>  ]
+<span id="L1036" class="LineNr">1036 </span>  <span class="Comment"># hit 'page-down' again</span>
+<span id="L1037" class="LineNr">1037 </span>  assume-console [
+<span id="L1038" class="LineNr">1038 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1039" class="LineNr">1039 </span>  ]
+<span id="L1040" class="LineNr">1040 </span>  run [
+<span id="L1041" class="LineNr">1041 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1042" class="LineNr">1042 </span>  ]
+<span id="L1043" class="LineNr">1043 </span>  <span class="Comment"># just second sandbox displayed</span>
+<span id="L1044" class="LineNr">1044 </span>  screen-should-contain [
+<span id="L1045" class="LineNr">1045 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1046" class="LineNr">1046 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1047" class="LineNr">1047 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
+<span id="L1048" class="LineNr">1048 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1049" class="LineNr">1049 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1050" class="LineNr">1050 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1051" class="LineNr">1051 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1052" class="LineNr">1052 </span>  ]
+<span id="L1053" class="LineNr">1053 </span>  <span class="Comment"># hit 'page-down' again</span>
+<span id="L1054" class="LineNr">1054 </span>  assume-console [
+<span id="L1055" class="LineNr">1055 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1056" class="LineNr">1056 </span>  ]
+<span id="L1057" class="LineNr">1057 </span>  run [
+<span id="L1058" class="LineNr">1058 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1059" class="LineNr">1059 </span>  ]
+<span id="L1060" class="LineNr">1060 </span>  <span class="Comment"># no change</span>
+<span id="L1061" class="LineNr">1061 </span>  screen-should-contain [
+<span id="L1062" class="LineNr">1062 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1063" class="LineNr">1063 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1064" class="LineNr">1064 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎1   edit          copy            delete         .</span>
+<span id="L1065" class="LineNr">1065 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1066" class="LineNr">1066 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1067" class="LineNr">1067 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1068" class="LineNr">1068 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1069" class="LineNr">1069 </span>  ]
+<span id="L1070" class="LineNr">1070 </span>  <span class="Comment"># hit 'page-up'</span>
+<span id="L1071" class="LineNr">1071 </span>  assume-console [
+<span id="L1072" class="LineNr">1072 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1073" class="LineNr">1073 </span>  ]
+<span id="L1074" class="LineNr">1074 </span>  run [
+<span id="L1075" class="LineNr">1075 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1076" class="LineNr">1076 </span>  ]
+<span id="L1077" class="LineNr">1077 </span>  <span class="Comment"># back to displaying both sandboxes without editor</span>
+<span id="L1078" class="LineNr">1078 </span>  screen-should-contain [
+<span id="L1079" class="LineNr">1079 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1080" class="LineNr">1080 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1081" class="LineNr">1081 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L1082" class="LineNr">1082 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1083" class="LineNr">1083 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1084" class="LineNr">1084 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1085" class="LineNr">1085 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1086" class="LineNr">1086 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1087" class="LineNr">1087 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1088" class="LineNr">1088 </span>  ]
+<span id="L1089" class="LineNr">1089 </span>  <span class="Comment"># hit 'page-up' again</span>
+<span id="L1090" class="LineNr">1090 </span>  assume-console [
+<span id="L1091" class="LineNr">1091 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1092" class="LineNr">1092 </span>  ]
+<span id="L1093" class="LineNr">1093 </span>  run [
+<span id="L1094" class="LineNr">1094 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1095" class="LineNr">1095 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1096" class="LineNr">1096 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1097" class="LineNr">1097 </span>  ]
+<span id="L1098" class="LineNr">1098 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
+<span id="L1099" class="LineNr">1099 </span>  screen-should-contain [
+<span id="L1100" class="LineNr">1100 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1101" class="LineNr">1101 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
+<span id="L1102" class="LineNr">1102 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1103" class="LineNr">1103 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1104" class="LineNr">1104 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1105" class="LineNr">1105 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1106" class="LineNr">1106 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1107" class="LineNr">1107 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1108" class="LineNr">1108 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1109" class="LineNr">1109 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1110" class="LineNr">1110 </span>  ]
+<span id="L1111" class="LineNr">1111 </span>  <span class="Comment"># hit 'page-up' again</span>
+<span id="L1112" class="LineNr">1112 </span>  assume-console [
+<span id="L1113" class="LineNr">1113 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1114" class="LineNr">1114 </span>  ]
+<span id="L1115" class="LineNr">1115 </span>  run [
+<span id="L1116" class="LineNr">1116 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1117" class="LineNr">1117 </span>  <span class="Conceal">¦</span> cursor:char <span class="Special">&lt;-</span> copy <span class="Constant">9251/␣</span>
+<span id="L1118" class="LineNr">1118 </span>  <span class="Conceal">¦</span> print <a href='../081print.mu.html#L4'>screen</a>, cursor
+<span id="L1119" class="LineNr">1119 </span>  ]
+<span id="L1120" class="LineNr">1120 </span>  <span class="Comment"># no change</span>
+<span id="L1121" class="LineNr">1121 </span>  screen-should-contain [
+<span id="L1122" class="LineNr">1122 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1123" class="LineNr">1123 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎␣                                                .</span>
+<span id="L1124" class="LineNr">1124 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1125" class="LineNr">1125 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1126" class="LineNr">1126 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1127" class="LineNr">1127 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1128" class="LineNr">1128 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1129" class="LineNr">1129 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎1   edit          copy            delete         .</span>
+<span id="L1130" class="LineNr">1130 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 2, 2                                         .</span>
+<span id="L1131" class="LineNr">1131 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎4                                                .</span>
+<span id="L1132" class="LineNr">1132 </span>  ]
+<span id="L1133" class="LineNr">1133 </span>]
+<span id="L1134" class="LineNr">1134 </span>
+<span id="L1135" class="LineNr">1135 </span><span class="muScenario">scenario</span> scrolling-manages-sandbox-index-correctly [
+<span id="L1136" class="LineNr">1136 </span>  <span class="Constant">local-scope</span>
+<span id="L1137" class="LineNr">1137 </span>  trace-until <span class="Constant">100/app</span>  <span class="Comment"># trace too long</span>
+<span id="L1138" class="LineNr">1138 </span>  assume-screen <span class="Constant">100/width</span>, <span class="Constant">10/height</span>
+<span id="L1139" class="LineNr">1139 </span>  <span class="Comment"># initialize environment</span>
+<span id="L1140" class="LineNr">1140 </span>  assume-resources [
+<span id="L1141" class="LineNr">1141 </span>  ]
+<span id="L1142" class="LineNr">1142 </span>  env:&amp;:environment <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L21'>new-programming-environment</a> <a href='../088file.mu.html#L11'>resources</a>, <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[]</span>
+<span id="L1143" class="LineNr">1143 </span>  <a href='004-programming-environment.mu.html#L445'>render-all</a> <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
+<span id="L1144" class="LineNr">1144 </span>  <span class="Comment"># create a sandbox</span>
+<span id="L1145" class="LineNr">1145 </span>  assume-console [
+<span id="L1146" class="LineNr">1146 </span>  <span class="Conceal">¦</span> press ctrl-n
+<span id="L1147" class="LineNr">1147 </span>  <span class="Conceal">¦</span> type <span class="Constant">[add 1, 1]</span>
+<span id="L1148" class="LineNr">1148 </span>  <span class="Conceal">¦</span> press F4
+<span id="L1149" class="LineNr">1149 </span>  ]
+<span id="L1150" class="LineNr">1150 </span>  <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1151" class="LineNr">1151 </span>  screen-should-contain [
+<span id="L1152" class="LineNr">1152 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1153" class="LineNr">1153 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1154" class="LineNr">1154 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1155" class="LineNr">1155 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1156" class="LineNr">1156 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1157" class="LineNr">1157 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1158" class="LineNr">1158 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1159" class="LineNr">1159 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1160" class="LineNr">1160 </span>  ]
+<span id="L1161" class="LineNr">1161 </span>  <span class="Comment"># hit 'page-down' and 'page-up' a couple of times. sandbox index should be stable</span>
+<span id="L1162" class="LineNr">1162 </span>  assume-console [
+<span id="L1163" class="LineNr">1163 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1164" class="LineNr">1164 </span>  ]
+<span id="L1165" class="LineNr">1165 </span>  run [
+<span id="L1166" class="LineNr">1166 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1167" class="LineNr">1167 </span>  ]
+<span id="L1168" class="LineNr">1168 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+<span id="L1169" class="LineNr">1169 </span>  <span class="Comment"># cursor moves to first sandbox</span>
+<span id="L1170" class="LineNr">1170 </span>  screen-should-contain [
+<span id="L1171" class="LineNr">1171 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1172" class="LineNr">1172 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1173" class="LineNr">1173 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L1174" class="LineNr">1174 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1175" class="LineNr">1175 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1176" class="LineNr">1176 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1177" class="LineNr">1177 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1178" class="LineNr">1178 </span>  ]
+<span id="L1179" class="LineNr">1179 </span>  <span class="Comment"># hit 'page-up' again</span>
+<span id="L1180" class="LineNr">1180 </span>  assume-console [
+<span id="L1181" class="LineNr">1181 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2987'>page-up</a>
+<span id="L1182" class="LineNr">1182 </span>  ]
+<span id="L1183" class="LineNr">1183 </span>  run [
+<span id="L1184" class="LineNr">1184 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1185" class="LineNr">1185 </span>  ]
+<span id="L1186" class="LineNr">1186 </span>  <span class="Comment"># back to displaying both sandboxes as well as editor</span>
+<span id="L1187" class="LineNr">1187 </span>  screen-should-contain [
+<span id="L1188" class="LineNr">1188 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1189" class="LineNr">1189 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1190" class="LineNr">1190 </span><span class="Constant">  </span><span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎─────────────────────────────────────────────────.</span>
+<span id="L1191" class="LineNr">1191 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎0   edit          copy            delete         .</span>
+<span id="L1192" class="LineNr">1192 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1193" class="LineNr">1193 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1194" class="LineNr">1194 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1195" class="LineNr">1195 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1196" class="LineNr">1196 </span>  ]
+<span id="L1197" class="LineNr">1197 </span>  <span class="Comment"># hit 'page-down'</span>
+<span id="L1198" class="LineNr">1198 </span>  assume-console [
+<span id="L1199" class="LineNr">1199 </span>  <span class="Conceal">¦</span> press <a href='003-shortcuts.mu.html#L2789'>page-down</a>
+<span id="L1200" class="LineNr">1200 </span>  ]
+<span id="L1201" class="LineNr">1201 </span>  run [
+<span id="L1202" class="LineNr">1202 </span>  <span class="Conceal">¦</span> <a href='004-programming-environment.mu.html#L39'>event-loop</a> <a href='../081print.mu.html#L4'>screen</a>, <a href='../084console.mu.html#L23'>console</a>, env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L1203" class="LineNr">1203 </span>  ]
+<span id="L1204" class="LineNr">1204 </span>  <span class="Comment"># sandbox editor hidden; first sandbox displayed</span>
+<span id="L1205" class="LineNr">1205 </span>  <span class="Comment"># cursor moves to first sandbox</span>
+<span id="L1206" class="LineNr">1206 </span>  screen-should-contain [
+<span id="L1207" class="LineNr">1207 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                                                 run (F4)           .</span>
+<span id="L1208" class="LineNr">1208 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1209" class="LineNr">1209 </span>  <span class="Conceal">¦</span><span class="Constant"> .╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╎0   edit          copy            delete         .</span>
+<span id="L1210" class="LineNr">1210 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎add 1, 1                                         .</span>
+<span id="L1211" class="LineNr">1211 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎2                                                .</span>
+<span id="L1212" class="LineNr">1212 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎─────────────────────────────────────────────────.</span>
+<span id="L1213" class="LineNr">1213 </span>  <span class="Conceal">¦</span><span class="Constant"> .                                                  ╎                                                 .</span>
+<span id="L1214" class="LineNr">1214 </span>  ]
+<span id="L1215" class="LineNr">1215 </span>]
 </pre>
 </body>
 </html>
diff --git a/html/edit/006-sandbox-copy.mu.html b/html/edit/006-sandbox-copy.mu.html
index bc8aebb2..9cfcc416 100644
--- a/html/edit/006-sandbox-copy.mu.html
+++ b/html/edit/006-sandbox-copy.mu.html
@@ -210,7 +210,7 @@ if ('onhashchange' in window) {
 <span id="L148" class="LineNr">148 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
 <span id="L149" class="LineNr">149 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
 <span id="L150" class="LineNr">150 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
-<span id="L151" class="LineNr">151 </span>  _, _, copy-button-left:num, copy-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L339'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
+<span id="L151" class="LineNr">151 </span>  _, _, copy-button-left:num, copy-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L341'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
 <span id="L152" class="LineNr">152 </span>  copy-button-vertical-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L211'>within-range?</a> click-column, copy-button-left, copy-button-right
 <span id="L153" class="LineNr">153 </span>  <span class="muControl">return-unless</span> copy-button-vertical-area?, <span class="Constant">0/false</span>
 <span id="L154" class="LineNr">154 </span>  <span class="Comment"># finally, is sandbox editor empty?</span>
diff --git a/html/edit/007-sandbox-delete.mu.html b/html/edit/007-sandbox-delete.mu.html
index 27a07309..541a6c02 100644
--- a/html/edit/007-sandbox-delete.mu.html
+++ b/html/edit/007-sandbox-delete.mu.html
@@ -154,7 +154,7 @@ if ('onhashchange' in window) {
 <span id="L92" class="LineNr"> 92 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
 <span id="L93" class="LineNr"> 93 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
 <span id="L94" class="LineNr"> 94 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
-<span id="L95" class="LineNr"> 95 </span>  _, _, _, _, delete-button-left:num <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L339'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
+<span id="L95" class="LineNr"> 95 </span>  _, _, _, _, delete-button-left:num <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L341'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
 <span id="L96" class="LineNr"> 96 </span>  result <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L211'>within-range?</a> click-column, delete-button-left, sandbox-right-margin
 <span id="L97" class="LineNr"> 97 </span>]
 <span id="L98" class="LineNr"> 98 </span>
diff --git a/html/edit/008-sandbox-edit.mu.html b/html/edit/008-sandbox-edit.mu.html
index 6b13bd12..222335bb 100644
--- a/html/edit/008-sandbox-edit.mu.html
+++ b/html/edit/008-sandbox-edit.mu.html
@@ -193,7 +193,7 @@ if ('onhashchange' in window) {
 <span id="L131" class="LineNr">131 </span>  assert first-sandbox, <span class="Constant">[!!]</span>
 <span id="L132" class="LineNr">132 </span>  sandbox-left-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">left:offset</span>
 <span id="L133" class="LineNr">133 </span>  sandbox-right-margin:num <span class="Special">&lt;-</span> get *first-sandbox, <span class="Constant">right:offset</span>
-<span id="L134" class="LineNr">134 </span>  edit-button-left:num, edit-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L339'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
+<span id="L134" class="LineNr">134 </span>  edit-button-left:num, edit-button-right:num, _ <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L341'>sandbox-menu-columns</a> sandbox-left-margin, sandbox-right-margin
 <span id="L135" class="LineNr">135 </span>  edit-button-vertical-area?:bool <span class="Special">&lt;-</span> <a href='006-sandbox-copy.mu.html#L211'>within-range?</a> click-column, edit-button-left, edit-button-right
 <span id="L136" class="LineNr">136 </span>  <span class="muControl">return-unless</span> edit-button-vertical-area?, <span class="Constant">0/false</span>
 <span id="L137" class="LineNr">137 </span>  <span class="Comment"># finally, is sandbox editor empty?</span>
diff --git a/html/edit/009-sandbox-test.mu.html b/html/edit/009-sandbox-test.mu.html
index 93625606..92ec3f39 100644
--- a/html/edit/009-sandbox-test.mu.html
+++ b/html/edit/009-sandbox-test.mu.html
@@ -155,7 +155,7 @@ if ('onhashchange' in window) {
 <span id="L92" class="LineNr"> 92 </span>]
 <span id="L93" class="LineNr"> 93 </span>
 <span id="L94" class="LineNr"> 94 </span><span class="Comment"># include expected response when saving or restoring a sandbox</span>
-<span id="L95" class="LineNr"> 95 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L228'>&lt;end-save-sandbox&gt;</a></span> [
+<span id="L95" class="LineNr"> 95 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L230'>&lt;end-save-sandbox&gt;</a></span> [
 <span id="L96" class="LineNr"> 96 </span>  <span class="Delimiter">{</span>
 <span id="L97" class="LineNr"> 97 </span>  <span class="Conceal">¦</span> expected-response:text <span class="Special">&lt;-</span> get *curr, <span class="Constant">expected-response:offset</span>
 <span id="L98" class="LineNr"> 98 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> expected-response
@@ -164,7 +164,7 @@ if ('onhashchange' in window) {
 <span id="L101" class="LineNr">101 </span>  <span class="Delimiter">}</span>
 <span id="L102" class="LineNr">102 </span>]
 <span id="L103" class="LineNr">103 </span>
-<span id="L104" class="LineNr">104 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L432'>&lt;end-restore-sandbox&gt;</a></span> [
+<span id="L104" class="LineNr">104 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L434'>&lt;end-restore-sandbox&gt;</a></span> [
 <span id="L105" class="LineNr">105 </span>  <span class="Delimiter">{</span>
 <span id="L106" class="LineNr">106 </span>  <span class="Conceal">¦</span> filename <span class="Special">&lt;-</span> append filename, <span class="Constant">[.out]</span>
 <span id="L107" class="LineNr">107 </span>  <span class="Conceal">¦</span> contents <span class="Special">&lt;-</span> <a href='../088file.mu.html#L38'>slurp</a> <a href='../088file.mu.html#L11'>resources</a>, filename
@@ -192,7 +192,7 @@ if ('onhashchange' in window) {
 <span id="L129" class="LineNr">129 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox
 <span id="L130" class="LineNr">130 </span>  <span class="Conceal">¦</span> <span class="Comment"># toggle its expected-response, and save session</span>
 <span id="L131" class="LineNr">131 </span>  <span class="Conceal">¦</span> sandbox <span class="Special">&lt;-</span> <a href='009-sandbox-test.mu.html#L168'>toggle-expected-response</a> sandbox
-<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L215'>save-sandboxes</a> env, <a href='../088file.mu.html#L11'>resources</a>
+<span id="L132" class="LineNr">132 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L217'>save-sandboxes</a> env, <a href='../088file.mu.html#L11'>resources</a>
 <span id="L133" class="LineNr">133 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L623'>hide-screen</a> <a href='../081print.mu.html#L4'>screen</a>
 <span id="L134" class="LineNr">134 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> render-sandbox-side <a href='../081print.mu.html#L4'>screen</a>, env, <a href='001-editor.mu.html#L123'>render</a>
 <span id="L135" class="LineNr">135 </span>  <span class="Conceal">¦</span> <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='004-programming-environment.mu.html#L511'>update-cursor</a> <a href='../081print.mu.html#L4'>screen</a>, recipes, current-sandbox, sandbox-in-focus?, env
@@ -246,7 +246,7 @@ if ('onhashchange' in window) {
 <span id="L183" class="LineNr">183 </span>]
 <span id="L184" class="LineNr">184 </span>
 <span id="L185" class="LineNr">185 </span><span class="Comment"># when rendering a sandbox, color it in red/green if expected response exists</span>
-<span id="L186" class="LineNr">186 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L292'>&lt;render-sandbox-response&gt;</a></span> [
+<span id="L186" class="LineNr">186 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L294'>&lt;render-sandbox-response&gt;</a></span> [
 <span id="L187" class="LineNr">187 </span>  <span class="Delimiter">{</span>
 <span id="L188" class="LineNr">188 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-response
 <span id="L189" class="LineNr">189 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>, row
@@ -255,17 +255,17 @@ if ('onhashchange' in window) {
 <span id="L192" class="LineNr">192 </span>  <span class="Conceal">¦</span> response-is-expected?:bool <span class="Special">&lt;-</span> equal expected-response, sandbox-response
 <span id="L193" class="LineNr">193 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
 <span id="L194" class="LineNr">194 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-if</span> response-is-expected?:bool
-<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">1/red</span>, row
+<span id="L195" class="LineNr">195 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">1/red</span>, row
 <span id="L196" class="LineNr">196 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
 <span id="L197" class="LineNr">197 </span>  <span class="Conceal">¦</span> <span class="Delimiter">{</span>
 <span id="L198" class="LineNr">198 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> <span class="muControl">break-unless</span> response-is-expected?:bool
-<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">2/green</span>, row
+<span id="L199" class="LineNr">199 </span>  <span class="Conceal">¦</span> <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-response, left, right, <span class="Constant">2/green</span>, row
 <span id="L200" class="LineNr">200 </span>  <span class="Conceal">¦</span> <span class="Delimiter">}</span>
 <span id="L201" class="LineNr">201 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+render-sandbox-end</span>
 <span id="L202" class="LineNr">202 </span>  <span class="Delimiter">}</span>
 <span id="L203" class="LineNr">203 </span>]
 <span id="L204" class="LineNr">204 </span>
-<span id="L205" class="LineNr">205 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L306'>&lt;end-render-sandbox-reset-hidden&gt;</a></span> [
+<span id="L205" class="LineNr">205 </span><span class="muRecipe">before</span> <span class="Constant"><a href='005-sandbox.mu.html#L308'>&lt;end-render-sandbox-reset-hidden&gt;</a></span> [
 <span id="L206" class="LineNr">206 </span>  *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>,<span class="Constant"> 0</span>
 <span id="L207" class="LineNr">207 </span>]
 </pre>
diff --git a/html/edit/010-sandbox-trace.mu.html b/html/edit/010-sandbox-trace.mu.html
index 2cf2dc0f..39714aa5 100644
--- a/html/edit/010-sandbox-trace.mu.html
+++ b/html/edit/010-sandbox-trace.mu.html
@@ -304,13 +304,13 @@ if ('onhashchange' in window) {
 <span id="L241" class="LineNr">241 </span>]
 <span id="L242" class="LineNr">242 </span>
 <span id="L243" class="LineNr">243 </span><span class="Comment"># when rendering a sandbox, dump its trace before response/warning if display-trace? property is set</span>
-<span id="L244" class="LineNr">244 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L283'>&lt;render-sandbox-results&gt;</a></span> [
+<span id="L244" class="LineNr">244 </span><span class="muRecipe">after</span> <span class="Constant"><a href='005-sandbox.mu.html#L285'>&lt;render-sandbox-results&gt;</a></span> [
 <span id="L245" class="LineNr">245 </span>  <span class="Delimiter">{</span>
 <span id="L246" class="LineNr">246 </span>  <span class="Conceal">¦</span> display-trace?:bool <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">display-trace?:offset</span>
 <span id="L247" class="LineNr">247 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> display-trace?
 <span id="L248" class="LineNr">248 </span>  <span class="Conceal">¦</span> sandbox-trace:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">trace:offset</span>
 <span id="L249" class="LineNr">249 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-trace  <span class="Comment"># nothing to print; move on</span>
-<span id="L250" class="LineNr">250 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-trace, left, right, <span class="Constant">245/grey</span>, row
+<span id="L250" class="LineNr">250 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-trace, left, right, <span class="Constant">245/grey</span>, row
 <span id="L251" class="LineNr">251 </span>  <span class="Delimiter">}</span>
 <span id="L252" class="LineNr">252 </span><span class="Constant">  <a href='010-sandbox-trace.mu.html#L252'>&lt;render-sandbox-trace-done&gt;</a></span>
 <span id="L253" class="LineNr">253 </span>]
diff --git a/html/edit/011-errors.mu.html b/html/edit/011-errors.mu.html
index 8c7c0a38..b6e5e3f6 100644
--- a/html/edit/011-errors.mu.html
+++ b/html/edit/011-errors.mu.html
@@ -72,14 +72,14 @@ if ('onhashchange' in window) {
 <span id="L9" class="LineNr">  9 </span>  <span class="Constant">local-scope</span>
 <span id="L10" class="LineNr"> 10 </span>  <span class="Constant">load-ingredients</span>
 <span id="L11" class="LineNr"> 11 </span>  recipes:&amp;:editor <span class="Special">&lt;-</span> get *env, <span class="Constant">recipes:offset</span>
-<span id="L12" class="LineNr"> 12 </span>  in:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L609'>editor-contents</a> recipes
+<span id="L12" class="LineNr"> 12 </span>  in:text <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L611'>editor-contents</a> recipes
 <span id="L13" class="LineNr"> 13 </span>  <a href='../088file.mu.html#L11'>resources</a> <span class="Special">&lt;-</span> <a href='../088file.mu.html#L127'>dump</a> <a href='../088file.mu.html#L11'>resources</a>, <span class="Constant">[lesson/recipes.mu]</span>, in
 <span id="L14" class="LineNr"> 14 </span>  recipe-errors:text <span class="Special">&lt;-</span> reload in
 <span id="L15" class="LineNr"> 15 </span>  *env <span class="Special">&lt;-</span> put *env, <span class="Constant">recipe-errors:offset</span>, recipe-errors
 <span id="L16" class="LineNr"> 16 </span>  <span class="Comment"># if recipe editor has errors, stop</span>
 <span id="L17" class="LineNr"> 17 </span>  <span class="Delimiter">{</span>
 <span id="L18" class="LineNr"> 18 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> recipe-errors
-<span id="L19" class="LineNr"> 19 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
+<span id="L19" class="LineNr"> 19 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L210'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
 <span id="L20" class="LineNr"> 20 </span>  <span class="Conceal">¦</span> errors-found? <span class="Special">&lt;-</span> copy <span class="Constant">1/true</span>
 <span id="L21" class="LineNr"> 21 </span>  <span class="Conceal">¦</span> <span class="muControl">return</span>
 <span id="L22" class="LineNr"> 22 </span>  <span class="Delimiter">}</span>
@@ -91,7 +91,7 @@ if ('onhashchange' in window) {
 <span id="L28" class="LineNr"> 28 </span>  recipe-errors:text <span class="Special">&lt;-</span> get *env, <span class="Constant">recipe-errors:offset</span>
 <span id="L29" class="LineNr"> 29 </span>  <span class="Delimiter">{</span>
 <span id="L30" class="LineNr"> 30 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> recipe-errors
-<span id="L31" class="LineNr"> 31 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
+<span id="L31" class="LineNr"> 31 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L210'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, <span class="Constant">[errors found     ]</span>, <span class="Constant">1/red</span>
 <span id="L32" class="LineNr"> 32 </span>  <span class="Delimiter">}</span>
 <span id="L33" class="LineNr"> 33 </span>]
 <span id="L34" class="LineNr"> 34 </span>
@@ -99,7 +99,7 @@ if ('onhashchange' in window) {
 <span id="L36" class="LineNr"> 36 </span>  <span class="Delimiter">{</span>
 <span id="L37" class="LineNr"> 37 </span>  <span class="Conceal">¦</span> recipe-errors:text <span class="Special">&lt;-</span> get *env, <span class="Constant">recipe-errors:offset</span>
 <span id="L38" class="LineNr"> 38 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> recipe-errors
-<span id="L39" class="LineNr"> 39 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, recipe-errors, left, right, <span class="Constant">1/red</span>, row
+<span id="L39" class="LineNr"> 39 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, recipe-errors, left, right, <span class="Constant">1/red</span>, row
 <span id="L40" class="LineNr"> 40 </span>  <span class="Delimiter">}</span>
 <span id="L41" class="LineNr"> 41 </span>]
 <span id="L42" class="LineNr"> 42 </span>
@@ -132,7 +132,7 @@ if ('onhashchange' in window) {
 <span id="L69" class="LineNr"> 69 </span>  <span class="Conceal">¦</span> <span class="muControl">break-if</span> sandboxes-completed-successfully?
 <span id="L70" class="LineNr"> 70 </span>  <span class="Conceal">¦</span> error-index-text:text <span class="Special">&lt;-</span> to-text error-index
 <span id="L71" class="LineNr"> 71 </span>  <span class="Conceal">¦</span> status:text <span class="Special">&lt;-</span> <a href='../061text.mu.html#L506'>interpolate</a> <span class="Constant">[errors found (_)    ]</span>, error-index-text
-<span id="L72" class="LineNr"> 72 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L208'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, status, <span class="Constant">1/red</span>
+<span id="L72" class="LineNr"> 72 </span>  <span class="Conceal">¦</span> <a href='005-sandbox.mu.html#L210'>update-status</a> <a href='../081print.mu.html#L4'>screen</a>, status, <span class="Constant">1/red</span>
 <span id="L73" class="LineNr"> 73 </span>  <span class="Delimiter">}</span>
 <span id="L74" class="LineNr"> 74 </span>]
 <span id="L75" class="LineNr"> 75 </span>
@@ -171,7 +171,7 @@ if ('onhashchange' in window) {
 <span id="L108" class="LineNr">108 </span>  <span class="Conceal">¦</span> sandbox-errors:text <span class="Special">&lt;-</span> get *sandbox, <span class="Constant">errors:offset</span>
 <span id="L109" class="LineNr">109 </span>  <span class="Conceal">¦</span> <span class="muControl">break-unless</span> sandbox-errors
 <span id="L110" class="LineNr">110 </span>  <span class="Conceal">¦</span> *sandbox <span class="Special">&lt;-</span> put *sandbox, <span class="Constant">response-starting-row-on-screen:offset</span>,<span class="Constant"> 0</span>  <span class="Comment"># no response</span>
-<span id="L111" class="LineNr">111 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L356'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-errors, left, right, <span class="Constant">1/red</span>, row
+<span id="L111" class="LineNr">111 </span>  <span class="Conceal">¦</span> row, <a href='../081print.mu.html#L4'>screen</a> <span class="Special">&lt;-</span> <a href='005-sandbox.mu.html#L358'>render-text</a> <a href='../081print.mu.html#L4'>screen</a>, sandbox-errors, left, right, <span class="Constant">1/red</span>, row
 <span id="L112" class="LineNr">112 </span>  <span class="Conceal">¦</span> <span class="Comment"># don't try to print anything more for this sandbox</span>
 <span id="L113" class="LineNr">113 </span>  <span class="Conceal">¦</span> <span class="muControl">jump</span> <span class="Constant">+render-sandbox-end</span>
 <span id="L114" class="LineNr">114 </span>  <span class="Delimiter">}</span>
diff --git a/sandbox/005-sandbox.mu b/sandbox/005-sandbox.mu
index bf05d266..89feed60 100644
--- a/sandbox/005-sandbox.mu
+++ b/sandbox/005-sandbox.mu
@@ -173,6 +173,7 @@ def run-sandboxes env:&:environment, resources:&:resources, screen:&:screen -> e
     loop
   }
   <run-sandboxes-end>
+  $system [./snapshot_lesson]
 ]
 
 # load code from disk
diff --git a/snapshot_lesson b/snapshot_lesson
new file mode 100755
index 00000000..2a943c37
--- /dev/null
+++ b/snapshot_lesson
@@ -0,0 +1,11 @@
+#!/bin/sh
+# Hacky little helper called from edit/ and sandbox/ apps to save a snapshot
+# of lesson/ using git.
+
+test -d lesson/.git || exit 0  # give up if it's not a git repo
+
+cd lesson
+# explicitly say '--all' for git 1.9
+git add --all .
+# bug in git: git diff -q messes up --exit-code
+git diff HEAD --exit-code >/dev/null || git commit -a -m . >/dev/null
author	Kartik K. Agaram <vc@akkartik.com>	2017-03-12 00:31:55 -0800
committer	Kartik K. Agaram <vc@akkartik.com>	2017-03-12 00:34:02 -0800
commit	2c53c3d0a921aec9825946be8dc37eff95b95485 (patch)
tree	598e12608182300a97529082e317b36373ce6a36
parent	465229a22a68f9c5cb94ba7853c44328f1bf85c1 (diff)
download	mu-2c53c3d0a921aec9825946be8dc37eff95b95485.tar.gz