anchor.diff:      (:color . (0 0 0))
       (:alpha . 1d0)
       (:visual . t)
  -    (:collision . t)))
  +    (:collision . t)
  +    (:type . nil)))
   
   (defun draw-option (options key)
     (alist-get-default options key *draw-options*))
  
positive.code:                                (color (draw-option options :color))
                                 (alpha (draw-option options :alpha))
                                 (visual (draw-option options :visual))
                                 (collision (draw-option options :collision)))
    (list* (cons :no-shadow no-shadow)
           (cons :color color)
           (cons :alpha alpha)
           (cons :visual visual)
           (cons :collision collision)
           options))
  
  (defun draw-options (&rest options-plist)
  
negative.code: (defun fold-scene-graph-frames (function initial-value scene-graph)
    (fold-tree-set function initial-value (scene-graph-frames scene-graph)))
  
  (defun prefix-scene-graph (prefix scene-graph &key
                                                  (prefix-parents t))
    (let ((frames))
      (do-scene-graph-frames (frame (scene-graph scene-graph) (scene-graph frames))
        (let ((frame (copy-structure frame))
              (parent (scene-frame-parent frame)))
          (setf (scene-frame-name frame)
                (rope prefix (scene-frame-name frame)))
          (when (and parent prefix-parents)
            (setf (scene-frame-parent frame)
                  (rope prefix parent)))
          (when (scene-frame-joint-p frame)
  