anchor.diff:     (target-location :initform nil :accessor target-location)
      (structure :initarg :structure :accessor enemy-structure)
      (death-tick :initform nil :accessor death-tick)
  -   (growth-tick :initform nil :accessor growth-tick)))
  +   (growth-tick :initform nil :accessor growth-tick)
  +   (growth-rate :initarg :growth-rate :accessor growth-rate)
  +   (max-size :initarg :max-size :accessor max-size)))
   
   (defmethod update ((enemy enemy))
     (let ((location (cell-location (pos enemy))))
  
positive.code: 
  
  ;;;; 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)
  
negative.code: (defconstant* enemy-death-ticks 64)
  (defconstant* enemy-growth-completion-ticks 64)
  (defconstant* enemy-flexibility 1.5)
  
  (defclass enemy ()
    ((pos :initarg :pos :accessor pos)
  