Reverting larger currently-executing-line pointer

Not compatible with Firefox, and not clear how to make it work in both
browsers.

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

@@ -26,7 +26,7 @@
     height: 100%
     right: -10px
     border: 1px solid transparent
-    
+
   span.code-background
     border-width: 124px 76px 64px 40px
     border-image: url(/images/level/code_editor_background_border.png) 124 76 64 40 fill round
@@ -132,23 +132,31 @@
         @include animation(progress-bar-stripes 0.5s linear infinite)
 
     &:not(.user-code-problem)
-      .ace_gutter-cell.executing:not(.ace_error):not(.ace_warning):not(.ace_info):after
+      .ace_gutter-cell.executing:not(.ace_error):not(.ace_warning):not(.ace_info)
+        margin-left: 1px
+        background-image: url(data:image/png;base64,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)
+        background-position: 0px center
 
-        // Experimenting with a larger executing-line-pointer
-        content: "\e072"
-        position: relative
-        top: -31px
-        left: -39px
-        display: inline-block
-        font-family: 'Glyphicons Halflings'
-        font-style: normal
-        font-weight: normal
-        line-height: 1
-        color: white
-        text-shadow: 0 0 5px black, 0 0 5px black, 0 0 5px black
-        font-size: 39px
-        -webkit-font-smoothing: antialiased
-        -moz-osx-font-smoothing: grayscale
+      // .ace_gutter-cell.executing:not(.ace_error):not(.ace_warning):not(.ace_info):after
+      // 
+      //   // Experimenting with a larger executing-line-pointer
+      //   content: "\e072"
+      //   position: relative
+      //   left: -39px
+      //   font-family: 'Glyphicons Halflings'
+      //   font-style: normal
+      //   font-weight: normal
+      //   color: white
+      //   text-shadow: 0 0 5px black, 0 0 5px black, 0 0 5px black
+      //   -webkit-font-smoothing: antialiased
+      //   -moz-osx-font-smoothing: grayscale
+      // 
+      //   // Chrome likes these, but Firefox does not
+      //   // TODO: Figure out how to make the executing gutter arrow big, and compatible
+      //   display: inline-block
+      //   top: -31px
+      //   line-height: 1
+      //   font-size: 39px
 
     .ace_gutter-cell.executed:not(.ace_error):not(.ace_warning):not(.ace_info)
       margin-left: 1px