First draft of logic to work out where the code entry points should be.

app/styles/play/level/tome/spell.sass

@@ -144,7 +144,7 @@
       background-position: 0px center
 
     .ace_gutter-cell.entry-point:after
-      content: attr(data-content)
+      content: " "
       display: inline-block
       position: relative
       left: -49px
@@ -153,14 +153,6 @@
       height: 38px
       overflow: visible
 
-      color: white
-      line-height: 39px
-      font-size: 16px
-      text-align: center
-      text-shadow: -1px 0 2px black, 1px 0 2px black, 0 -1px 2px black, 0 1px 2px black
-      -webkit-font-smoothing: antialiased
-      -moz-osx-font-smoothing: grayscale
-      
       background-image: url(data:image/png;base64,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)
 
     .ace_gutter-cell.entry-point:not(.next-entry-point):after

app/views/play/level/tome/SpellView.coffee

@@ -812,6 +812,14 @@ module.exports = class SpellView extends CocoView
     @_singleLineCommentRegex = new RegExp "[ \t]*#{commentStart}[^\"'\n]*", 'g'
     @_singleLineCommentRegex
 
+  lineWithCodeRegex: ->
+    if @_lineWithCodeRegex
+      @_lineWithCodeRegex.lastIndex = 0
+      return @_lineWithCodeRegex
+    commentStart = commentStarts[@spell.language] or '//'
+    @_lineWithCodeRegex = new RegExp "^[ \t]*(?!( |]t|#{commentStart}))+", 'g'
+    @_lineWithCodeRegex
+
   commentOutMyCode: ->
     prefix = if @spell.language is 'javascript' then 'return;  ' else 'return  '
     comment = prefix + commentStarts[@spell.language]
@@ -995,25 +1003,54 @@ module.exports = class SpellView extends CocoView
 
   highlightEntryPoints: ->
     lines = @aceDoc.$lines
+    originalLines = @spell.originalSource.split '\n'
     session = @aceSession
-    top = Math.floor @ace.renderer.getScrollTopRow()
-    seenOne = false
-    entryPointLines = []
+    commentStart = commentStarts[@spell.language] or '//'
+    seenAnEntryPoint = false
+    previousLine = null
+    previousLineHadComment = false
+    previousLineHadCode = false
+    previousLineWasBlank = false
+    pastIntroComments = false
     for line, index in lines
       session.removeGutterDecoration index, 'entry-point'
       session.removeGutterDecoration index, 'next-entry-point'
-      if line.indexOf('if') isnt -1
+
+      lineHasComment = @singleLineCommentRegex().test line
+      lineHasCode = line.trim()[0] and not _.string.startsWith line.trim(), commentStart
+      lineIsBlank = /^[ \t]*$/.test line
+      lineHasExplicitMarker = line.indexOf('∆') isnt -1
+
+      originalLine = originalLines[index]
+      lineHasChanged = line isnt originalLine
+
+      isEntryPoint = lineIsBlank and previousLineHadComment and not previousLineHadCode and pastIntroComments
+      if isEntryPoint and lineHasChanged
+        movedIndex = originalLines.indexOf previousLine
+        if movedIndex isnt -1 and line is originalLines[movedIndex + 1]
+          lineHasChanged = false
+        else
+          isEntryPoint = false
+
+      if lineHasExplicitMarker
+        if lineHasChanged
+          if originalLines.indexOf(line) isnt -1
+            lineHasChanged = false
+            isEntryPoint = true
+        else
+          isEntryPoint = true
+
+      if isEntryPoint
         session.addGutterDecoration index, "entry-point"
-        if not seenOne
+        if not seenAnEntryPoint
           session.addGutterDecoration index, 'next-entry-point'
-          seenOne = true
-        entryPointLines.push index
-    scrolledAwayLines = 0
-    #while entryPointLines.length and entryPointLines[0] < top
-    #  entryPointLines.shift()
-    #  ++scrolledAwayLines
-    $(@ace.container).find('.ace_gutter-cell.entry-point').each (index, el) ->
-      $(el).attr('data-content', scrolledAwayLines + index + 1)
+          seenAnEntryPoint = true
+
+      previousLine = line
+      previousLineHadComment = lineHasComment
+      previousLineHadCode = lineHasCode
+      previousLineWasBlank = lineIsBlank
+      pastIntroComments ||= lineHasCode or previousLineWasBlank
 
   onAnnotationClick: ->
     # @ is the gutter element