anchor.diff:  |=======================================================================
   
   Collectively, `x`, `y`, and `z` specify a three-dimensional point
  -within the light show’s [[frame of reference|show-space]] telling the
  +within the light show’s <<show_space#show-space,frame of reference>> telling the
   lights where to aim. When this vector is supplied to an
   <<effects#aim-effects,Aim Effect>>, it causes the attached lights to
   make the specified movement, if they are capable.
  
positive.code: 
  A more traditional way of aiming fixtures involves setting pan and
  tilt angles. Afterglow supports this approach as well, although even
  in this case you use angles expressed in the standard show [[frame of
  reference|show-space]] regardless of how the individual fixtures are
  hung. Pan Tilt parameters are an alternate way to work with
  <<effects#direction-effects,Direction Effects>>. The basic way to create one is to
  call:
  
  [source,clojure]
  ----
  
negative.code: 
  The rotations requested by `pan` and `tilt` jointly identify the
  direction the light should turn away from the audience. The result of
  the parameter is a direction vector in the light show’s
  <<show_space#show-space,frame of reference>> telling the lights which
  direction they should point. When this vector is supplied to a
  <<effects#direction-effects,Direction Effect>>, it causes the attached
  lights to make the specified movement, if they are capable.
  
  