anchor.diff:    (with-slots (parent offset veloc accel) missile
       (let ((nearest-enemy (nearest-object missile 'enemy)))
         (if nearest-enemy
  -          (setf veloc (* (unit veloc) (min (abs veloc) 8d0))
  -                accel (unit (- (offset nearest-enemy) offset)))
  +          (setf veloc (* (unit veloc) (min (abs veloc) 12d0))
  +                accel (* (unit (- (offset nearest-enemy) offset)) 2d0))
             (setf accel 0)))))
   
   (defmethod collide ((thopter thopter) event)
  
positive.code:                            :image (make-instance 'image :name :enemy)
                             :health 4 :timer 20
                             :firepower (max 1 (ceiling w 3))
                             :difficulty (floor w 3))))))
  
  (defmethod game-init ((game thopter-game))
    (let* ((size #c(800 600))
  
negative.code:       (make-instance 'missile
                       :parent parent 
                       :offset (+ offset (/ (x size) 2) #c(0 -4)) :depth -1
                       :veloc (+ veloc #c(0 -4))
                       :image (make-instance 'image :name :missile)
                       :timer 120))))
  
  