anchor.diff:      (defun update-absorb-force ()
         "Integrate position during animation"
         ;; Update acceleration, velocity, position
  -      (update-tilt-absorb)
         (let* ((accel (* 5d-5 (abs (cos (* incidence (/ pi 180))))))
   	     (now ((@ (new (*date)) get-time)))
   	     (dt (/ (* timefactor (- now (or time now))) 1000)))
  
positive.code:       (when (> rotation 180)
  	(setq rotation (- rotation 360)))
        (update-tilt))
      
      (defun init-tilt-controls ()
        "Initialize tilt controls for tilting/rotating the sail"
  
negative.code: 	    rotation 0
  	    absorbed 100)
        ;; Arrow key events
        ((@ ($ (@ document body)) keydown)
         #'(lambda (e)
  	   (tilt-key-event e)))
        ;; Clicking on arrow images
        ((@ ($ "#up") click) #'(lambda (e) (up)))
        ((@ ($ "#down") click) #'(lambda (e) (down)))
  