+(define* (move scene x y #:optional (z 0))
+ (make-scene
+ "move"
+ (lambda ()
+ (gl-translate (calculate x)
+ (calculate y)
+ (calculate z))
+ (display-scene scene))))
+
+(define* (scale scene x #:optional (y x) (z y))
+ (make-scene
+ "scale"
+ (lambda ()
+ (gl-scale (calculate x)
+ (calculate y)
+ (calculate z))
+ (display-scene scene))))
+
+(define (over . scenes)