anchor.diff:     (halo :initform (make-instance 'halo) :accessor halo)
      (movement-actions :initform '() :accessor movement-actions)
      (claiming :initform nil :accessor claiming-p)
  -   (lives :initarg :lives :accessor lives)))
  +   (lives :initarg :lives :accessor lives)
  +   (score :initform 0 :accessor score)))
   
   (defmethod initialize-instance :after ((player player) &rest initargs)
     (declare (ignore initargs))
  
positive.code:            (when (= (incf (death-tick enemy)) enemy-death-ticks)
               (remove-object enemy)))
            ((= cell-claimed (cell-ref location (grid enemy)))
             (setf (death-tick enemy) 0))
            ((need-new-target-p location enemy)
             (setf (target-location enemy) (choose-target-cell location enemy)))))
    (when (null (death-tick enemy))
  
negative.code:   (do-objects (player :type 'player)
      (player-die player)))
  
  (defun enemy-die (enemy)
    (setf (death-tick enemy) 0)
    (do-objects (player :type 'player)
      (increment-score (floor (score player) 10) player)))
  
  
  ;;;; Game
  