anchor.diff:    (when (and (parent bullet) (typep (event-hit event) 'enemy))
       (detach (parent bullet) bullet)))
   
  +(defmethod alarm ((bullet bullet) event)
  +  (when (parent bullet)
  +    (detach (parent bullet) bullet)))
  +
   (defmethod collide ((missile missile) event)
     (with-slots (parent offset size depth veloc) missile
       (when (and parent (or (typep (event-hit event) 'enemy)
  
positive.code: 
  (defmethod alarm ((enemy enemy) event)
    (with-slots (parent offset size veloc timer) enemy
      (setf timer (+ 2 (mt19937:random 25)))
      (shoot enemy event)))
  
  (defmethod collide ((enemy enemy) event)
  
negative.code: 
  (defmethod collide ((bullet enemy-bullet) event)
    (when (and (parent bullet) (typep (event-hit event) 'thopter))
      (detach (parent bullet) bullet)))
  
  (defmethod alarm ((bullet enemy-bullet) event)
    (when (parent bullet)
      (detach (parent bullet) bullet)))
  
  (defmethod update ((enemy enemy) event)
  