anchor.diff:        (sdl2:push-event :quit)))
   
     (defun init ()
  -    (gl:enable :depth-test)
  -    (gl:viewport 0 0 *width* *height*)
  +    (gl:enable :cull-face :lighting :light0 :depth-test)
       (gl:matrix-mode :projection)
  -    (gl:ortho (- *x*) *x* (- *y*) *y* (- *x*) *x*)
  +    (gl:load-identity)
  +;    (gl:frustum -2 2 -2 2 1 10)
  +    (gl:ortho 0 2 0 2 -2 10)
  +;    (glu:perspective 45.0 *ratio* 0.1 10)
       (gl:matrix-mode :modelview)
       (gl:load-identity)
       (gl:clear-color 19/255 19/255 39/255 1.0) ; #131327 background color
  
positive.code:     (sdl2:with-window (win :w *width* :h *height* :flags '(:shown :opengl))
        (sdl2:with-gl-context (gl-context win)
          (sdl2:gl-make-current win gl-context)
          (init)
  
          (sdl2:with-event-loop (:method :poll)
  
negative.code:            (:keysym keysym)
             (keyup-actions (sdl2:scancode-value keysym)))
  
            ;; Used to draw a square.
            (:idle
             ()
             (gl:clear :color-buffer :depth-buffer)
             (gl:begin :quad-strip)
             (gl:material :front :ambient-and-diffuse #(1.0 0.0 0.0 1.0))
             (gl:vertex 0.0 1.0 2.0)
             (gl:vertex 1.0 1.0 2.0)
             (gl:vertex 1.0 0.0 2.0)
             (gl:vertex 0.0 0.0 2.0)
             (gl:end)
             (gl:flush)
             (sdl2:gl-swap-window win))
  