anchor.diff:   explain what this default orientation is, so that people patching
    your fixture can figure out the proper angle information to tell
    Afterglow if they hung it in a different orientation, as explained in
  - <<show_space#show-space,Show Space>>.
  + <<show_space#show-space,Show Space>>. The `:pan-center` value should
  + tilt the light so it is aimed exactly along the show Z axis when also
  + tilted to `:tilt-center`.
   
   Many fixtures can pan more than once around a full circle, so you may
   have a choice of values to supply here, all of which pan the fixture
  
positive.code: room to maneuver without having to flip to the opposite end of the pan
  range regardless of how the fixture has been hung.
  
  |`:pan-half-circle`
  
  |.
  
  |`:tilt-center`
  
  |.
  
  |`:tilt-half-circle`
  
  |.
  
  |===
  
  == Channel Specifications
  
  == Head Specifications
  
  TODO: Finish this page.
  
  
negative.code:  was created. As desrcibed above, some fixtures can be configured to
   have different &ldquo;personalities&rdquo; which use a different
   number of DMX channels and provide a different set of features. Their
   fixture definition functions will use a `mode` argument to determine
   the mode in which the fixture is operating, and return an appropriate
   map. That map will include the chosen mode keyword as the value at
   this key.
  