anchor.diff:  thing. If the effect doesn’t want to do anything this frame, it can
   simply return an empty assigner list.
   
  -5.  Once all the assigners have been collected, Each assigner’s
  +. Once all the assigners have been collected, Each assigner’s
   http://deepsymmetry.org/afterglow/doc/afterglow.effects.html#var-assign[assign]
   function is called, again passing in the show and the metronome
   snapshot, the target which is being assigned (a DMX channel in a show
  
positive.code: When it is time to determine the next set of values to send to the
  show’s patched fixtures, this is what happens:
  
  1.  The first thing Afterglow does is take a
  http://deepsymmetry.org/afterglow/doc/afterglow.rhythm.html#var-ISnapshot[snapshot]
  of the show
  https://github.com/brunchboy/afterglow/wiki/Metronomes[metronome] to
  
negative.code: objects into appropriate DMX channel values for the target that is being
  assigned.
  
  . Finally, the resulting buffers of DMX values, with zeros in any
  channels which were not affected by assigners, are sent to their
  corresponding universes, causing the lights to produce the desired
  effects.
  