anchor.diff:      (setf (pos player) (cell-center-position row col))))
   
   (defmethod update ((player player))
  +  (when (null (movement-actions player))
  +    (maybe-queue-movement-actions player))
  +  (when-let (action (pop (movement-actions player)))
  +    (funcall action))
     (halo-update (halo player)))
   
   (defmethod render ((player player))
  
positive.code:         (draw-circle (- 5 i) 30 t))
        (gl:color 0.0 0.0 1.0 (halo-value (halo player)))
        (draw-circle 5))))
  
  
  
negative.code: 
  ;;;; Player
  
  (defconstant player-movement-steps 3)
  
  (defclass player ()
    ((pos :accessor pos)
     (row :initarg :row :accessor row)
     (col :initarg :col :accessor col)
     (grid :initarg :grid :accessor grid)
     (halo :initform (make-instance 'halo) :accessor halo)
     (movement-actions :initform '() :accessor movement-actions)))
  
  (defmethod initialize-instance :after ((player player) &rest initargs)
    (declare (ignore initargs))
  