10MODE 1
   11plotcode=85
   20REM Xbase, Ybase are the address of the cell which you get if
   30REM you ask for cell 0,0
   40PROCmain
   50END
   60 
   70DEFPROC_set_colour(Colour1,Colour2,Colour3,Colour4)
   80   GCOL 0,64
   90 
  100   pair0 = (Colour1 AND 2) OR ((Colour2 AND 2) DIV 2)
  110   pair0 = pair0 * 4 + pair0
  120   pair1 = ((Colour1 AND 1)*2) OR (Colour2 AND 1)
  130   pair1 = pair1 * 4 + pair1
  140   pair2 = (Colour3 AND 2) OR ((Colour4 AND 2) DIV 2)
  150   pair2 = pair2 * 4 + pair2
  160   pair3 = ((Colour3 AND 1)*2) OR (Colour4 AND 1)
  170   pair3 = pair3 * 4 + pair3
  180 
  190   VDU pair0*16 OR pair1
  200   VDU pair2*16 OR pair3
  210   VDU pair0*16 OR pair1
  220   VDU pair2*16 OR pair3
  230ENDPROC
  240 
  250DEFPROC_box(Xl,Yb,Xr,Yt)
  251IF Xl=Xr OR Yb=Yt THEN ENDPROC
  260IF Xl < 0 OR Xr < 0 THEN Xl=Xl+80:Xr=Xr+80
  261IF Yb < 0 OR Yt < 0 THEN Yb=Yb+64:Yt=Yt+64
  263IF Yt>64 THEN Yt=Yt-64:Yb=Yb-64
  280   Xl = Xl*(1280 DIV 80):Xr = Xr*(1280 DIV 80)-(1280 DIV 320)
  290   Yb = Yb*(1024 DIV 64):Yt = Yt*(1024 DIV 64)-(1024 DIV 256)
  300   MOVE Xl,Yb
  310   MOVE Xl,Yt
  320   PLOT plotcode,Xr,Yb
  330   PLOT plotcode,Xr,Yt
  340ENDPROC
  350 
  360 
  370DEFPROCscroll
  380 
  390Screen=&3000-(Xbase*8)+((Ybase DIV 2)*640)
  400IF Screen<&3000 THEN Screen=Screen+&5000
  410IF Screen>=&8000 THEN Screen=Screen-&5000
  420 
  430*FX19
  440VDU 23;12,Screen DIV 2048;0;0;0
  450VDU 23;13,Screen MOD 2048 DIV 8;0;0;0
  460ENDPROC
  470 
  480 
  490DEFFNjoyleft
  500AD=(ADVAL(1) DIV 64)
  501Xstep=1:IF AD>512+256+128+64 THEN Xstep=10
  502=AD > 512+256
  510 
  520DEFFNjoyright
  530AD=(ADVAL(1) DIV 64)
  531Xstep=1:IF AD<64 THEN Xstep=10
  532=AD < 256
  540 
  550DEFFNjoydown
  560AD=(ADVAL(2) DIV 64)
  561Ystep=2:IF AD<16 THEN Ystep=16
  562=AD < 256
  570 
  580DEFFNjoyup
  590AD=(ADVAL(2) DIV 64)
  591Ystep=2:IF AD>512+256+128+64+32+16 THEN Ystep=16
  592=AD > 512+256
  600 
  610 
  620DEFPROCmain
  630   PRINT TAB(0,0);"?";
  640   Xbase = 0: Ybase = 0
  650   REPEAT
  660      IF FNjoyleft THEN PROCmoveleft
  670      IF FNjoyright THEN PROCmoveright
  680      IF FNjoyup THEN PROCmoveup
  690      IF FNjoydown THEN PROCmovedown
  700      IF (ADVAL(0) MOD 2) = 1 THEN PROCNewBox(39,30,41,34)
  710   UNTIL FALSE
  720ENDPROC
  730 
  740DEFPROCmoveleft
  741PROCwipe(0,0,Xstep,64)
  750   IF Xbase = 0 THEN PROCmoveup:Xbase = 80-Xstep ELSE Xbase = Xbase-Xstep
  760   PROCscroll
  770ENDPROC
  780 
  790DEFPROCmoveright
  791PROCwipe(80-Xstep,0,80,64)
  800   IF Xbase = 80-Xstep THEN PROCmovedown:Xbase = 0 ELSE Xbase = Xbase+Xstep
  810   PROCscroll
  820ENDPROC
  830 
  840DEFPROCmoveup
  841PROCwipe(0,64-Ystep,80,64)
  850   IF Ybase = 64-Ystep THEN Ybase = 0 ELSE Ybase = Ybase+Ystep
  860   PROCscroll
  870ENDPROC
  880 
  890DEFPROCmovedown
  891PROCwipe(0,0,80,Ystep)
  900   IF Ybase = 0 THEN Ybase = 64-Ystep ELSE Ybase = Ybase-Ystep
  910   PROCscroll
  920ENDPROC
  930 
 1010 
 1020DEFPROCA(XL,YB,XR,YT)
 1040PROC_box(XL-Xbase,YB-Ybase,XR-Xbase,YT-Ybase)
 1050ENDPROC
 1060 
 1070DEFPROCB(XL,YB,XR,YT)
 1090PROC_box(XL-Xbase,YB-Ybase,XR-Xbase,YT-Ybase)
 1100ENDPROC
 1110 
 1120DEFPROCC(XL,YB,XR,YT)
 1140PROC_box(XL-Xbase,YB-Ybase+2,XR-Xbase,YT-Ybase+2)
 1150ENDPROC
 1160 
 1170DEFPROCD(XL,YB,XR,YT)
 1190PROC_box(XL-Xbase,YB-Ybase+2,XR-Xbase,YT-Ybase+2)
 1200ENDPROC
 2000 
 2010DEFPROCNewBox(XL,YB,XR,YT)
 2020   IF XR <= Xbase THEN PROCCD(XL,YB,XR,YT):ENDPROC
 2030   IF XL >= Xbase THEN PROCAB(XL,YB,XR,YT):ENDPROC
 2031   IF YB >= Ybase THEN PROCAD(XL,YB,XR,YT):ENDPROC
 2032   IF YT <= Ybase THEN PROCBC(XL,YB,XR,YT):ENDPROC
 2040   PROCCD(XL,YB,Xbase,YT)
 2050   PROCAB(Xbase,YB,XR,YT)
 2060ENDPROC
 2070 
 2080DEFPROCCD(XL,YB,XR,YT)
 2090   IF YT <= Ybase-2 THEN PROCC(XL,YB,XR,YT):ENDPROC
 2100   IF YB >= Ybase-2 THEN PROCD(XL,YB,XR,YT):ENDPROC
 2200   PROCC(XL,YB,XR,Ybase-2)
 2210   PROCD(XL,Ybase-2,XR,YT)
 2220ENDPROC
 2230 
 2240DEFPROCAB(XL,YB,XR,YT)
 2250   IF YT <= Ybase THEN PROCB(XL,YB,XR,YT):ENDPROC
 2260   IF YB >= Ybase THEN PROCA(XL,YB,XR,YT):ENDPROC
 2270   PROCB(XL,YB,XR,Ybase)
 2280   PROCA(XL,Ybase,XR,YT)
 2290ENDPROC
 2300 
 2310DEFPROCAD(XL,YB,XR,YT)
 2320   IF XR <= Xbase THEN PROCD(XL,YB,XR,YT):ENDPROC
 2330   IF XL >= Xbase THEN PROCA(XL,YB,XR,YT):ENDPROC
 2340   PROCD(XL,YB,Xbase,YT)
 2350   PROCA(Xbase,YB,XR,YT)
 2360ENDPROC
 2370 
 2380DEFPROCBC(Xl,YB,XR,YT)
 2390   IF XR <= Xbase THEN PROCC(XL,YB,XR,YT):ENDPROC
 2400   IF XL >= Xbase THEN PROCB(XL,YB,XR,YT):ENDPROC
 2410   PROCC(XL,YB,Xbase,YT)
 2420   PROCB(Xbase,YB,XR,YT)
 2430ENDPROC
 5000 
 5010DEFPROCwipe(XL,YB,XR,YT)
 5020   GCOL 2,0
 5021   PROCNewBox(XL,YB,XR,YT)
 5030   GCOL 0,3
 5040ENDPROC