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:        (sdl:clear-display sdl:*black*)
         (update-lst (cdr *bodies*))
         (draw-bodies *bodies*)
        (sdl:update-display))))
  
  (defun main ()
  
negative.code: 			    'nil))
  	  *bodies*))
  
  (defmacro edit-parameter (id parameter value)
    `(setf (,parameter (nth (position ,id
  				    (mapcar #'(lambda (x) (id x)) *bodies*))
  			  *bodies*))
  	 ,value))
  
  (defun sdl-init ()
    "Initialize SDL environment"
  