anchor.diff:  		  :color-key (sdl:color :r 255 :b 255)))
   	   (background (when *background-image-filename*
   			 (sdl-image:load-image (namestring 
  -						(merge-pathnames *background-image-filename*))))))
  +						(merge-pathnames *background-image-filename*)))))
  +	   (current-cell 0))
        (sdl:with-events ()
          (:quit-event () (prog1 t
   			 (sdl:free image)))
  
positive.code: 		  (sdl:draw-surface background)
  	      (sdl:clear-display *bg-color*))
  	      (sdl:set-cell (sdl:rectangle 
  			     :x (* *current-cell* *cell-width*) 
  			     :y (* *cell-row* *cell-height*)
  			     :w *cell-width*
  			     :h *cell-height*)
  			    :surface image)
  	      (sdl:draw-surface-at-* image (/ *screen-width* 2) (/ *screen-height* 2))
  	      (if (< (+ *pause-between-loops* *num-frames*) *current-cell*)
  		  (setf *current-cell* 0)
  		  (incf *current-cell*))
  	      (sdl:update-display)
  	      (when (not *running*)
  		(sdl:push-quit-event)))))))
  
negative.code: (defparameter *cell-width* 15)
  (defparameter *cell-height* 14)
  (defparameter *cell-row* 0)
  (defparameter *number-of-frames* 15)
  (defparameter *frame-rate* 60)
  (defparameter *screen-width* 500)
  (defparameter *screen-height* 500)
  (defparameter *bg-color* sdl:*black*)
  