anchor.diff:  
   (defun clear-light (light)
     (setf (light-state light) nil)
  -  (when *current-framebuffer*
  +  (when (and *current-framebuffer*
  +             *light-position*)
       (let ((fb-addr (+ +physical-map-base+
                         (framebuffer-base-address *current-framebuffer*)
  +                      (if (eql *light-position* :bottom)
  +                          (* (1- (framebuffer-height *current-framebuffer*))
  +                             (framebuffer-pitch *current-framebuffer*))
  +                          0)
                         (* (light-index light) 32 4))))
         (dotimes (i 32)
           (setf (sys.int::memref-unsigned-byte-32 fb-addr i) 0)))))
  
positive.code:                                 (if (boundp '*light-decay-time*)
                                      *light-decay-time*
                                      0)))
    (when *current-framebuffer*
      (let ((fb-addr (+ +physical-map-base+
                        (framebuffer-base-address *current-framebuffer*)
                        (* (light-index light) 32 4)))
            (colour (if (light-state light)
                        (light-colour light)
  
negative.code: ;;;; This code is licensed under the MIT license.
  
  (in-package :mezzano.supervisor)
  
  (defvar *light-position* nil
    "Control the position of the status light.
  Can be :TOP to position them at the top of the screen, :BOTTOM to position them at the bottom, or NIL to disable them entirely.")
  
  (defstruct (framebuffer
               (:area :wired))
  