anchor.diff:  (defun on-button-down-event (button)  
     "These function are run when a mouse-button-down event is detected."
     (declare (ignore button))
  -  (when (sdl:mouse-left-p)
  -    (setf *random-color*
  -          (sdl:color :r (random 255)
  -                     :g (random 255)
  -                     :b (random 255)))))
  +  (when (sdl:mouse-left-p)))
   
   (defun on-quit-event ()
     "Run this code when the quit-event is detected prior to exiting."
  
positive.code:     (make-instance 'player :x 0
                             :y 0
                             :color sdl:*red*))
    (:method ((mob mob))
      (push (make-instance 'mob :x (random 200)
                                :y (random 200)
                                :color sdl:*red*) *mob*)))
  
  (defun text (string x y)
    "Writes text to the default sdl surface"
  
negative.code:   (:documentation "Renders a unit onto the default sdl window.")
    (:method ((player player) x y)
      (sdl:draw-surface-at-* (lookup-sprite 'player) (* x 8) (* y 8)))
    ;; (:method ((mob mob) x y)
    ;;   (sdl:draw-box-* (x-pos *mob*) (y-pos *mob*) 2 2
    ;;                   :color (color *player*)))
    (:method ((sprite sdl:surface) x y)    
      (sdl:draw-surface-at-* sprite x y)))
  
  