anchor.diff:      (setf (game-wave screen) (make-instance 'wave-controller :parent root)
             (game-quit screen) (make-instance 'quit-controller :parent root)
             (game-background screen)
  -          (make-instance 'background-controller :parent root :timer 2)
  +          (make-instance 'background-controller :parent root :timer 0)
             (players-left screen)
             (make-instance 'players-left-controller :parent root)
             (game-sound screen)
  
positive.code:            (num-tiles (length tiles))
             (tile-size (size (first tiles))))
        (iter (for x from 0 below (x size) by (x tile-size))
              (let ((y (+ (- (y tile-size)) 2)))
                (make-instance 'tile
                               :parent parent
                               :offset (complex x y)
                               :veloc #c(0 1/2)
                               :image (nth (mt19937:random num-tiles)
                                           tiles)
                               :depth 100)))
        (setf timer (- (* (y tile-size) 2) 2)))))
  
  (defmethod (setf players-left) :after (value (left players-left-controller))
    (when (<= value 0)
  
negative.code:                   (make-instance 'tile
                                   :parent root
                                   :offset (complex x y)
                                   :veloc #c(0 1)
                                   :image (nth (mt19937:random num-tiles)
                                               tiles)
                                   :depth 100))))))
  