anchor.diff:  (defsetf sprite-flip sprite-set-flip)
   
   (defun create-sprite (x y width height texture &key (bbox (make-bbox)) (flip :none)
  -                                                    (angle 0))
  +                                                    (angle 0) (color #(1.0 1.0 1.0 1.0)))
     (let ((sp (make-sprite :texture texture
  +                         :color color
                            :x x :y y :width width :height height
                            :bbox bbox :flip flip
                            :shape (create-rectangle-shape x y (+ x width) (+ y height)))))
  
positive.code:   bbox
    shape
    texture
    (flip :none))
  
  (defun sprite-set-flip (it value)
  
negative.code:     sp))
  
  (defun render-sprite (sp)
    (set-color (sprite-color sp))
    (select-texture (sprite-texture sp) :env-mode :modulate)
    (render-shape (sprite-shape sp)))
  
  