anchor.diff:  http://deepsymmetry.org/afterglow/doc/afterglow.effects.cues.html#var-cue[cue]
   function creates a cue. At its most basic, you pass in two parameters,
   `show-key` which is the keyword that will be used to add the
  -cue&rsquo;s effect to the show when the cue is triggered, ending any
  +cue's effect to the show when the cue is triggered, ending any
   other effect running under that same keyword, and `effect`, which is a
   function that will be called when the cue is triggered, and whose
   responsibility is to create and return the effect that the cue should
  
positive.code: |Sets the color of the cue within the grid for hinting about its
  purpose and relatedness to other cues, to help operators learn and
  understand the interface. If not specified, white is used.
  
  |===
  
  
negative.code: To trigger a cue, simply press the corresponding pad on a physical
  interface, or click within the grid cell in the web interface. The
  effect associated with the cue will be created and added to the show,
  and the grid cell will be lightened to indicate that the cue's
  effect is running. If the cue ends itself after a period, the grid
  interface will be updated to reflect that as well.
  
  To end a cue's effect before it would naturally end (or because
  it is open-ended and does not end until asked to), simply press the
  pad corresponding to the running cue (or, again, click the grid cell
  in the web interface). The effect will be asked to end. Some effects
  