anchor.diff:  
   == Overview
   
  +This section starts out by describing the basic effect types which act
  +as building blocks for an Afterglow light show, then goes on to
  +introduce the <<scenes,scenes>> and <<chases,chases>> that you can use
  +to group and sequence these building blocks into a show that evolves
  +over time, driven by the show's metronome.
  +
   When creating an effect, you assign one or more
   <<fixture_definitions#fixture-definitions,Fixtures>> to it, and it
   will generate control values for only those fixtures. The fixture
  -channels affected by the effect depend on the kind of effect it is,
  -and are grouped into several primary categories. The simplest kinds of
  -effects apply to a single channel per fixture, or perhaps per head, if
  -the fixture has multiple independent light-emitting heads. A very
  -common single-channel effect is the <<dimmer-effects,dimmer effect>>.
  +channels that will be manipulated by the effect depend on the kind of
  +effect it is, and are grouped into several primary categories. The
  +simplest kinds of effects apply to a single channel per fixture, or
  +perhaps per head, if the fixture has multiple independent
  +light-emitting heads. A very common single-channel effect is the
  +<<dimmer-effects,dimmer effect>>.
   
   Many effects assign <<color-effects,colors>> to lights, which often
   involves multiple channels. RGB fixtures will use three channels, one
  
positive.code: &rarr; 1&hellip; while a value of `:bounce` would give you 1 &rarr; 2
  &rarr; 3 &rarr; 2 &rarr; 1 &rarr; 2 &rarr; 3 &rarr; 2&hellip;.
  
  ==== Conditional Effects
  
  The
  http://deepsymmetry.org/afterglow/doc/afterglow.effects.html#var-conditional-effect[conditional-effect]
  
negative.code: level of individual DMX channel values with
  <<channel-effects,channel effects>>.
  
  As mentioned above, there are a number of ways to combine these
  effects. If you have a group of effects that you want to start and
  stop at the same time, you can group them into a <<scenes,scene>>. To
  smoothly transition from one effect to another you can use a
  <<fades,fade>>, and either side of the fade can be a scene. Or you can
  fade to or from a <<blank-effects,blank effect>>, or sequence a whole
  list of effects or scenes using a <<chases,chase>>.
  
  <<conditional-effects,Conditional effects>> and
  <<variable-effects,variable effects>> are designed to make it easy for
  effects to influence and interact with each other by responding to and
  setting show variables. Finally, Afterglow includes some examples of
  how to build up <<complex-effects,special-purpose effects>>, which can
  be fun in themselves, and also serve as templates and inspiration for
  whole new kinds of effects you create on your own.
  
  == Basic Effect Types
  
  