anchor.diff:  
    
  -;;;; Level timer
  -
  -(defconstant* enemy-growth-ticks 1000)
  -
  -(defclass level-timer ()
  -  ())
  -
  -(defmethod update ((timer level-timer))
  -  (when (and (plusp *tick*)
  -             (zerop (mod *tick* enemy-growth-ticks)))
  -    (do-objects (enemy :type 'enemy)
  -      (enemy-grow enemy))))
  -
  --
   ;;;; Game
   
   (defclass consix-window (game-window)
  
positive.code: 
  (define-level (consix :test-order '(player enemy t))
    (grid :named grid)
    (level-timer)
    (player :lives 3 :loc (location (1- grid-rows) (floor grid-cols 2)) :grid grid)
    (enemy :pos (vec -10 0) :structure (list 0.0) :grid grid)
    (enemy :pos (vec +10 0) :structure (list 0.0) :grid grid))
  
  (defun game ()
    (glut:display-window
  
negative.code:     (increment-score (floor (score player) 10) player)))
  
  (defun enemy-grow (enemy)
    (when (< (length (enemy-structure enemy)) (max-size enemy))
      (setf (growth-tick enemy) 0)
      (appendf (enemy-structure enemy) (list (lastcar (enemy-structure enemy))))))
            
  (defun enemy-check-growth (enemy)
    (when (and (null (growth-tick enemy))
               (plusp *tick*)
               (zerop (mod *tick* (growth-rate enemy))))
      (enemy-grow enemy))
    (when (growth-tick enemy)
      (setf (growth-tick enemy)
            (if (= enemy-growth-completion-ticks (growth-tick enemy))
  