anchor.diff:  (defvar *sun-M* 1.99e30)
   (defvar *earth-M* 5.97e24)
   
  +(defclass point () 
  +  ((x :type number
  +      :accessor point-x
  +      :initarg :x
  +      :initform 0)
  +   (y :type number
  +      :accessor point-y
  +      :initarg :y
  +      :initform 0)))
  +
  +(defvar *screen-size* (make-instance 'point :x 640 :y 480))
  +(defvar *sun-pos* (make-instance 'point :x 0 :y 0))
  +
  +(defun mid-x (val)
  +  (/ (slot-value val 'x) 2))
  +
  +(defun mid-y (val)
  +  (/ (slot-value val 'y) 2))
  +
  +(defun pos2pos (pos)
  +  "Converts position relative to centre in km to sdl coordinates"
  +  (sdl:point :x (+ (mid-x *screen-size*) (/ (point-x pos) 468750))
  +             :y (+ (mid-y *screen-size*) (/ (point-y pos) 468750))))
  +
   (defun newpos (oldpos)
     )
   
   (defun proto ()
     (sdl:with-init ()
  -    (sdl:window 640 480 :title-caption "OrbSim Prototype v1.04e-23")
  +    (sdl:window (point-x *screen-size*)
  +                (point-y *screen-size*)
  +                :title-caption "OrbSim Prototype v1.04e-23")
       (setf (sdl:frame-rate) 60)
       
       (sdl:with-events ()
  
positive.code: 
  (ql:quickload "lispbuilder-sdl")
  (ql:quickload "lispbuilder-sdl-gfx")
  
  
negative.code:          (sdl:push-quit-event)))
        (:idle ()  (sdl:clear-display sdl:*black*)
  
         (sdl-gfx:draw-filled-circle
           (pos2pos *sun-pos*)
           10 
           :color sdl:*yellow*)
  
  