big-bang Simple scheme program

simple-scheme-crash.scm

(define scn (empty-scene))

(define width (image-width scn))
(define height (image-height scn))

(define (render-circle r)
  (place-image
    (circle r "solid" "red")
    (/ width 2)
    (/ height 2)
    scn))

(define (next-circle r)
  (modulo (+ r 1) 100))

(big-bang 0
          (on-tick next-circle)
          (on-draw render-circle))