anchor.diff:                (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
  
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:        (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 ()
  