supertux/data/images/objects/keys/key.sprite

(supertux-sprite
      (action
        (name "silver-right")
		(hitbox 0 2 48 28)
        (images "key_silver.png"))
	
	  (action
		(name "silver-left")
		(hitbox 0 2 48 28)
		(mirror-action "silver-right"))
)