anchor.diff:    (unless with-shockwave
       (setf (drawable explosion)
             nil)))
  -                                
  +
   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;;;
   ;;; purely visual objects
  
positive.code:    (selectable
      :initform t)))
  
  (sb-mop:finalize-inheritance (find-class 'unit))
  
  (defmethod initialize-instance :after ((unit unit) &key (weapons ()) (group ()) (dont-add nil))
    (unless dont-add
  
negative.code:     (setf (slot-value (parent child) 'children)
            (remove child (children (parent child))))
      (setf (slot-value child 'parent) nil)))
  
  
  (defmethod acquaint ((parent composite) (children cons))
    (dolist (child children)
  