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: (defconstant* enemy-death-ticks 64)
  (defconstant* enemy-growth-completion-ticks 64)
  (defconstant* enemy-flexibility 1.5)
  (defconstant* enemy-max-size 8)
  
  (defclass enemy ()
    ((pos :initarg :pos :accessor pos)
  
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))
  