anchor.diff:     :save-game
      :send
      :update-game
  +
  +   ;; actor.lisp
  +   :actor
  +   :mobile
  +   :veloc
  +   :accel
   
      ))
   
  
positive.code:    :update
     :sprite
     :image
     :mobile
     :veloc
     :accel
  
     ;; actor.lisp
     :event
     :event-type
     :event-mixin
  
negative.code:    :bound-key-up-p
     :bind-key-up
     :unbind-key-up
  
     ;; game.lisp
     :game
  