anchor.diff:          (velocity unit)
           (rotate (make-point 0 (max-speed unit))
                   (rot unit)))
  -  
  +
     (call-next-method))
   
   
  
positive.code:  (setf (alpha beam)
         (min 1
              (+ 0.1 (alpha beam)))
    
          (pos (first (children beam)))
          (pos (source-weapon beam))
          (pos (second (children beam)))
  
negative.code:     (make-instance (first (queue factory))
                     :owner (owner factory)
                     :group (group factory)
                     :pos (pos factory))))
  