anchor.diff:         (sdl:clear-display sdl:*black*)
          (update-lst (cdr *bodies*))
          (draw-bodies *bodies*)
  +       
  +       (setf *a* (append *a* (list (pos2pos (pos (cadr *bodies*))))))
  +       (draw-trails)
  +	
         (sdl:update-display))))
   
   (defun main ()
  
positive.code: 		 
  
  (defparameter *G* 6.67e-11) ; Gravitational Constant
  (defparameter *screen-size* (make-instance 'point :x 320 :y 320))
  
  (defparameter *earth* (make-body :pos-x 0 :pos-y 1e8 
  				 :vel-x 1e6 :vel-y 0 
  
negative.code:               (y *screen-size*)
                :title-caption "OrbSim Prototype v1.09e-23")
      (setf (sdl:frame-rate) 60))
  
  (defparameter *a* (list))
  
  (defun draw-trails ()
    (mapc #'(lambda (i) (sdl:draw-pixel i
  		       :color sdl:*red*))
  	*a*))
  
  
  (defun sdl-main-loop ()
    ; Define key events
  