10PROCmain
   20END
   30DEFPROCNewBox(XL,YB,XR,YT)
   40 
   50IF XL < Xbase AND Xbase < XR THEN PROCNewBox(XL,YB,Xbase,YT):                                                     PROCNewBox(Xbase,YB,XR,YT):ENDPROC
   60IF YB < Ybase AND Ybase < YT THEN PROCNewBox(XL,YB,XR,Ybase):                                                     PROCNewBox(XL,Ybase,XR,YT):ENDPROC
   70 
   80PROC_box((XL+Xbase) MOD 80,    (YB+Ybase) MOD 64,                                        (XR+Xbase) MOD 80,    (YT+Ybase) MOD 64)
   90 
  100ENDPROC
  110 
  120DEFPROC_set_colour(Colour1,Colour2,Colour3,Colour4)
  130   VDU 18,0,64
  140 
  150   pair0 = (Colour1 AND 2) OR ((Colour2 AND 2) DIV 2)
  160   pair0 = pair0 * 4 + pair0
  170   pair1 = ((Colour1 AND 1)*2) OR (Colour2 AND 1)
  180   pair1 = pair1 * 4 + pair1
  190   pair2 = (Colour3 AND 2) OR ((Colour4 AND 2) DIV 2)
  200   pair2 = pair2 * 4 + pair2
  210   pair3 = ((Colour3 AND 1)*2) OR (Colour4 AND 1)
  220   pair3 = pair3 * 4 + pair3
  230 
  240   VDU pair0*16 OR pair1
  250   VDU pair2*16 OR pair3
  260   VDU pair0*16 OR pair1
  270   VDU pair2*16 OR pair3
  280ENDPROC
  290 
  300DEFPROC_box(Xl,Yb,Xr,Yt)
  310   Xl = Xl*(1280 DIV 80):Xr = Xr*(1280 DIV 80)-(1280 DIV 320)
  320   Yb = Yb*(1024 DIV 64):Yb = Yb*(1024 DIV 64)-(1024 DIV 256)
  330   MOVE Xl,Yb
  340   MOVE Xl,Yt
  350   PLOT 85,Xr,Yb
  360   PLOT 85,Xr,Yt
  370ENDPROC