foo.lisp

(ql:quickload :lispbuilder-sdl)
(defvar *SIZE* 800)
(defvar *SHADES* 50)
(defvar *STEP* (/ *SIZE* *SHADES*))
(defvar *COL* 0)

(defun box (n)
  (cond ((>= n *SHADES*) nil)
        ((< n *SHADES*)
         (progn
           (setq *COL* (/ (* n 255) *SHADES*))
           (sdl:draw-box-* (* *STEP* n) 0 *STEP* *SIZE*
                           :color (sdl:color :r *COL* :g *COL* :b *COL*))
           (box (+ n 1))))))

(sdl:with-init ()
  (sdl:window *SIZE* *SIZE* :title-caption "50 . Shades of Grey")
  (setf (sdl:frame-rate) 60)

  (sdl:with-events ()
    (:quit-event () t)
    (:key-down-event () (sdl:push-quit-event))
    (:idle ()
           (sdl:clear-display sdl:*black*)
           (box 0)
           (sdl:update-display))))