anchor.diff:  
       (defun force ()
         (let ((app (add-animation (add-target (add-reflection (add-projection (add-tilt (what))))))))
  -	(with-slots (camera reflectv absorb-arrow reflect-arrow update-tilt incidence accelfn timefactor force-arrow normal init sail-position) app
  +	(with-slots (camera reflectv absorb-force-arrow reflect-arrow update-tilt incidence accelfn timefactor force-arrow normal init sail-position) app
   	  ((@ camera position set) -4 -6 6)
   	  (setf
   	   timefactor 10
  
positive.code: 	 corners (corners mirror)
  	 projection (projection corners)
  	 incident (incident)
  	 absorb-arrow (new (3fn *arrow-helper incident origin 10 0xff0000))
  	 visibility
  	 (let ((visibility-super ((@ app superior) "visibility")))
  	   (lambda (bool)
  
negative.code: 	     (lambda ()
  	       (funcall init-super)
  	       ((@ sail-position add) force-arrow)
  	       ((@ sail-position add) absorb-force-arrow)
  	       ((@ sail-position add) reflect-arrow)))
  	   visibility
  	   (let ((vis-super ((@ app superior) "visibility")))
  