(define (draw_world world tail)
  (place-images
    (list (square 32 "solid" "white")
          (square 32 "solid" "blue")

          ;place-images: expects an image-list as first argument, given (list (object:image% ...) (object:image% ...) #<void>)
          (for ([i tail]) (square 32 "solid" "red"))
          )
    (list (make-posn (get_x world) (get_y world))
          (make-posn (get_fruit_x world) (get_fruit_y world))
          (for ([i tail]) (make-posn (tail_cell-x i) (tail_cell-y i)))
          )
    (empty-scene (screen_width world) (screen_height world) "black")
   ))