anchor.diff:  (defvar *position-buffer-object*)
   
   
  -
   (defmethod initialize-instance :after ((w test-window) &key &allow-other-keys)
     ;; GL setup can go here; your GL context is automatically active,
     ;; and this is done in the main thread.
   
     ;; if you (setf (idle-render window) t) it'll call RENDER as fast as
  -  ;; possible when not processing other events; suitable for games
  +  ;; possible when not processing other events - suitable for games
     (setf (idle-render w) t)
     (gl:clear-color 0 0 1 1)
     (gl:clear :color-buffer-bit)
     (gl:viewport 0 0 800 600)
   
  +  ;; with culling
     (gl:enable :cull-face)
     (gl:cull-face :back)
     (gl:front-face :cw)
   
  +  
     ;; shader stuff
     (initialize-program)
   
  
positive.code: 	   (vector
  	    (sb-cga:matrix*
  	     (sb-cga:rotate (vec3 0.0 0.0 (mod (/ (sdl2:get-ticks) 5000.0) (* 2 3.14159))))
  	     (sb-cga:translate (vec3 1.0 0.0 -1.0)))))  
    
    (gl:bind-buffer :array-buffer *position-buffer-object*)
    (%gl:enable-vertex-attrib-array 0)
  
negative.code: 
  
  (defparameter *rotate-x* -1.0)
  (defparameter *rotate-y* 0.0)
  (defparameter *zoom-z* -2.0)
  
  (defun draw-cube ()
    (gl:bind-vertex-array *vao*)
  