anchor.diff:             (:keysym keysym)
              (keyup-actions (sdl2:scancode-value keysym)))
   
  -          ;; Draws a square.
  +          ;; Used to draw a square.
             (:idle
              ()
              (gl:clear :color-buffer :depth-buffer)
  -           (gl:begin :quads)
  -           (gl:color 1.0 0.0 0.0)
  -           (gl:vertex -1.0 1.0 0.0)
  -           (gl:vertex 1.0 1.0 0.0)
  -           (gl:vertex 1.0 -1.0 0.0)
  -           (gl:vertex -1.0 -1.0 0.0)
  +           (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))
  
positive.code: ;(in-package #:cl-foo)
  
  (require :sdl2)
  
  (defparameter *width* 1280)
  (defparameter *height* 720)
  (defparameter *scale* 10)
  (defparameter *x* (* *width* (/ *scale* *height*)))
  (defparameter *y* *scale*)
  
  (defun main-loop ()
    (defun keydown-actions (scancode)
  
negative.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)
          (sdl2:hide-cursor)
          (init)
  
          (sdl2:with-event-loop (:method :poll)
  