Documentation: image.ss

;; forall(World):
   start         ;; Number Number -> true
   big-bang      ;; Number World -> true 
   on-tick-event ;; (World -> World) -> true
   on-key-event  ;; (KeyEvent World -> World) -> true 
   end-of-time   ;; -> World

   rectangle   ;; Number Number Color -> Image
   frame       ;; Number Number Color -> Image
   circle      ;; Number Color -> Image 
   disk        ;; Number Color -> Image 
   place-image ;; Image Number Number Scence -> Scene
   empty-scene ;; Number Number -> Scene 
   run-movie   ;; (Listof Image) -> true 

;; New syntax: 
   (update ⟨expression⟩ produce )