supertux/data/images/objects/bonus_block/retroblock.sprite

(supertux-sprite
      (action
         (fps 15)
         (name "normal")
         (images "box-full.png"
                 ))
      (action
         (name "empty")
         (surfaces
          (surface
           (diffuse-texture (file "box-empty.png"))
           (displacement-texture (file "displacement.png")))))
)