10 REM EXPLORE FOR OBJECT
   20 REM Keith Anderson
   30 REM (c) CET 1983 Published by BBC Publications
   40 REM version 2.0
   50 :
   60 REM PORT SETUP
   70 port = &FE60        :REM User port (see manual for details).
   80 ?&FE62 = 15         :REM 00001111;  0 = input;  1 = output
   90 PROCmotors_on
  100 :
  110 REM USER AREA
  120 Xfactor = 1.175     :REM Adjust slightly on inaccurate TV sets
  130 speedcontrol = 8
  140 :
  150 REM MAIN PROGRAM
  160 REM Detect arrow keys
  170 *FX 4,1
  180 MODE 7
  190 PROCsetup_general
  200 PROCsetup_program
  210 :
  220 ON ERROR IF ERR=17 THEN GOTO 240  ELSE PROCend:REPORT:PRINT " on line"ERL:END
  230 PROCintroduction
  240 MODE7
  250 IF (?port AND 32) THEN PROCnogo : PROCend : END :REM Check if Buggy connected
  260 PROCoff             :REM Cursor off
  270 REPEAT
  280 VDU 26              :REM Reset text & graphics windows
  290 CLS
  300 PROCmenu
  310 IF option=1 THEN MODE 4 : PROCgo1 : MODE 7
  320 UNTIL option=2
  330 :
  340 MODE 7
  350 PROCcomplete
  360 END
  370 :
  380 :
  390 REM PROCEDURES SPECIFICALLY FOR "EXPLORE FOR OBJECT"
  400 DEF PROCanti_clock_search
  410 FOR side = 1 TO 3
  420 PROChitobject
  430 PROCcrash (hit)
  440 PROCmove_bug (right,90,bumpers)
  450 PROCmove_bug (forwards,sidestep,bumpers)
  460 IF hit THEN ENDPROC :REM boundary
  470 PROCmove_bug (backwards,safedistance,nosensors)
  480 PROCmove_bug (left,90,bumpers)
  490 PROCmove_bug (forwards,safedistance+20,bumpers)
  500 IF hit THEN GOTO 430
  510 REM Found corner
  520 PROCmove_bug (backwards,safedistance+20,nosensors)
  530 PROCmove_bug (right,90,bumpers)
  540 PROCmove_bug (forwards,15,bumpers)
  550 PROCmove_bug (left,90,bumpers)
  560 PROCmove_bug (forwards,safedistance+(BF/FWD)+10,bumpers)
  570 PROCmove_bug (left,90,bumpers)
  580 PROCmove_bug (forwards,sidestep*1.5,bumpers)
  590 NEXT side
  600 PROChitobject
  610 PROCcrash (hit)
  620 ENDPROC
  630 :
  640 DEF PROCclock_search
  650 PROCcrash (hit)
  660 PROCmove_bug (left,180,bumpers)
  670 PROCmove_bug (forwards,BW/FWD,bumpers)
  680 PROCmove_bug (right,90,bumpers)
  690 PROCmove_bug (forwards,BW/FWD,bumpers)
  700 FOR try = 1 TO 3
  710 PROChitobject
  720 PROCcrash (hit)
  730 PROCmove_bug (left,90,bumpers)
  740 PROCmove_bu on line"ž:à
  230 PROCintroduction
  240 MODE7
  250 IF (?port AND 32) THEN PROCnogo : PROCend : END :REM Check if Buggy connected
  260 PROCoff             :REM Cursor off
  270 REPEAT
  280 VDU 26              :REM Reset text & graphics windows
  290 CLS
  300 PROCmenu
  310 IF option=1 THEN MODE 4 : PROCgo1 : MODE 7
  320 UNTIL option=2
  330 :
  340 MODE 7
  350 PROCcomplete
  360 END
  370 :
  380 :
  390 REM PROCEDURES SPECIFICALLY FOR "EXPLORE FOR OBJECT"
  400 DEF PROCanti_clock_search
  410 FOR side = 1 TO 3
  420 PROChitobject
  430 PROCcrash (hit)
  440 PROCmove_bug (right,90,bumpers)
  450 PROCmove_bug (forwards,sidestep,bumpers)
  460 IF hit THEN ENDPROC :REM boundary
  470 PROCmove_bug (backwards,safedistance,nosensors)
  480 PROCmove_bug (left,90,bumpers)
  490 PROCmove_bug (forwards,safedistance+20,bumpers)
  500 IF hit THEN GOTO 430
  510 REM Found corner
  520 PROCmove_bug (backwards,safedistance+20,nosensors)
  530 PROCmove_bug (right,90,bumpers)
  540 PROCmove_bug (forwards,15,bumpers)
  550 PROCmove_bug (left,90,bumpers)
  560 PROCmove_bug (forwards,safedistance+(BF/FWD)+10,bumpers)
  570 PROCmove_bug (left,90,bumpers)
  580 PROCmove_bug (forwards,sidestep*1.5,bumpers)
  590 NEXT side
  600 PROChitobject
  610 PROCcrash (hit)
  620 ENDPROC
  630 :
  640 DEF PROCclock_search
  650 PROCcrash (hit)
  660 PROCmove_bug (left,180,bumpers)
  670 PROCmove_bug (forwards,BW/FWD,bumpers)
  680 PROCmove_bug (right,90,bumpers)
  690 PROCmove_bug (forwards,BW/FWD,bumpers)
  700 FOR try = 1 TO 3
  710 PROChitobject
  720 PROCcrash (hit)
  730 PROCmove_bug (left,90,bumpers)
  740 PROCmove_bug (forwards,(BW*2)/FWD,bumpers)
  750 IF hit THEN ENDPROC
  760 PROCmove_bug (backwards,safedistance,nosensors)
  770 PROCmove_bug (right,90,bumpers)
  780 PROCmove_bug (forwards,safedistance+(BF/FWD),bumpers)
  790 IF hit THEN GOTO 720
  800 PROCmove_bug (right,90,bumpers)
  810 PROCmove_bug (forwards,(BW*3)/FWD,bumpers)
  820 NEXT try
  830 PROChitobject
  840 PROCcrash (hit)
  850 ENDPROC
  860 :
  870 DEF PROCdraw_object
  880 MOVE KLX,KLY
  890 MOVE KHX,KLY
  900 PLOT 85, KHX,KHY
  910 MOVE KLX,KHY
  920 PLOT 85, KLX,KLY
  930 ENDPROC
  940 :
  950 DEF PROCexplore_object
  960 KHX  = horiz * Xscale
  970 KHY  = vert  *  scale
  980 KLX  = 0
  990 KLY  = 0
 1000 PROCupdate
 1010 PROCcentre ("Press ESCAPE to exit program.",4)
 1020 grid_end = FALSE
 1030 PROCgrid_search
 1040 IF off_screen THEN grid_end = TRUE
 1050 IF grid_end THEN ENDPROC
 1060 PROCanti_clock_search
 1070 IF side<3 THEN PROCclock_search
 1080 PROCdraw_object
 1090 PROCcentre ("Object found, I want to go home!",4)
 1100 SOUND 1,-15,200,20
 1110 PROCspace (6)
 1120 PROCcentre ("",6)
 1130 ENDPROC
 1140 :
 1150 DEF PROCgo_home
 1160 LOCAL count,left_side,bottom
 1170 left_side  = FALSE
 1180 bottom     = FALSE
 1190 count = 0
 1200 REPEAT
 1210 count = count + 1
 1220 IF angle<>270 THEN PROCmove_bug (right,270-angle,bumpers)
 1230 PROCmove_bug (backwards,(14-BGX)/FWD,nosensors)
 1240 PROCmove_bug (forwards,(BGX-14)/FWD,bumpers)
 1250 IF hit=0 THEN left_side = TRUE
 1260 IF hit THEN PROCmove_bug (backwards,safedistance,nosensors)
 1270 IF left_side=TRUE AND bottom=FALSE AND count>1 AND KHX<horiz*Xscale THEN PROCmove_bug (backwards,(KHX/Xscale-BGX+6)/FWD+safedistance,nosensors)
 1280 PROCmove_bug (left,90,bumpers)
 1290 PROCmove_bug (backwards,(14-BGY)/FWD,nosensors)
 1300 PROCmove_bug (forwards,(BGY-14)/FWD,bumpers)
 1310 IF hit=0 THEN bottom = TRUE
 1320 IF hit THEN PROCmove_bug (backwards,safedistance,nosensors)
 1330 IF bottom=TRUE AND left_side=FALSE AND count>1 AND KHY<vert*scale THEN PROCmove_bug (backwards,(KHY/scale-BGY+6)/FWD+safedistance,nosensors)
 1340 UNTIL (BGX <= 14 AND BGY <= 14) OR count > 4
 1350 PROCmove_bug (right,180,bumpers)
 1360 IF count > 4 THEN SOUND 1,-15,200,20 : PROCcentre ("Someone is trying to confuse me !",4):PROCspace (6)
 1370 SOUND 1,-15,200,20
 1380 ENDPROC
 1390 :
 1400 DEF PROCget_ready1
 1410 VDU 26                   :REM Reset text and graphics windows
 1420 CLS
 1430 PROCscreen               :REM Draw "Instrument panel"
 1440 VDU 26                   :REM Reset text and graphics windows
 1450 PROCcentre (program_name$,1)
 1460 VDU 29,640-(horiz DIV 2*Xscale);320;:REM Set Graphics origin
 1470 PROCboundary (0,0,horiz,vert)
 1480 VDU 28,0,31,39,24        :REM Text window
 1490 PROCcalcpos
 1500 PROCcalcbug (GRX,GRY,0)
 1510 PROCdrawbug
 1520 ENDPROC
 1530 :
 1540 DEF PROCgo1
 1550 PROCscale
 1560 VDU 19,1,7;0;   :REM white foreground
 1570 VDU 19,0,1;0;   :REM red background
 1580 BGX = 14
 1590 BGY = 14
 1600 off_screen = FALSE
 1610 PROCget_ready1
 1620 PROCspace (6)
 1630 REPEAT UNTIL INKEY(nokey)
 1640 VDU 19,0,7,0,0,0 :REM White background
 1650 VDU 19,1,4,0,0,0 :REM Blue foreground
 1660 PROCcentre ("",6)
 1670 angle = 0
 1680 distance = 0
 1690 PROCexplore_object
 1700 PROCmove_bug (backwards,safedistance,nosensors)
 1710 PROCgo_home
 1720 PROCget_ready1
 1730 IF NOT grid_end THEN PROCdraw_object
 1740 IF NOT grid_end THEN PROCcentre ("Object is approx. "+STR$(INT((KHX-KLX)/Xscale+0.5))+" by "+STR$(INT((KHY-KLY)/scale+0.5))+" cms.",4)
 1750 IF grid_end THEN PROCcentre ("No object found.",4)
 1760 PROCupdate
 1770 PROCspace (6)
 1780 ENDPROC
 1790 :
 1800 DEF PROCgrid_search
 1810 LOCAL sweep1,sweep2
 1820 grid_end = FALSE
 1830 sweep1 = (vert-(BGY+BF+1))/FWD
 1840 sweep2 = (vert-(safedistance*FWD+(BF+1)*2))/FWD
 1850 sidestep = (BW*2)/FWD
 1860 PROCmove_bug (forwards,sweep1,bumpers)
 1870 IF hit OR off_screen THEN ENDPROC
 1880 PROCmove_bug (backwards,safedistance,nosensors)
 1890 PROCmove_bug (right,90,bumpers)
 1900 PROCmove_bug (forwards,sidestep,bumpers)
 1910 IF hit OR off_screen THEN ENDPROC
 1920 PROCmove_bug (right,90,bumpers)
 1930 PROCmove_bug (forwards,sweep2,bumpers)
 1940 IF hit OR off_screen THEN ENDPROC
 1950 PROCmove_bug (backwards,safedistance,nosensors)
 1960 PROCmove_bug (left,90,bumpers)
 1970 PROCmove_bug (forwards,sidestep,bumpers)
 1980 IF hit OR off_screen THEN ENDPROC
 1990 PROCmove_bug (left,90,bumpers)
 2000 PROCmove_bug (forwards,sweep2,bumpers)
 2010 GOTO 1870
 2020 :
 2030 DEF PROChitobject
 2040 IF angle=0   THEN KLY = FMY
 2050 IF angle=90  THEN KLX = FMX
 2060 IF angle=180 THEN KHY = FMY
 2070 IF angle=270 THEN KHX = FMX
 2080 ENDPROC
 2090 :
 2100 DEF PROCintroduction
 2110 CLS
 2120 PROCoff
 2130 PROCdouble (CHR$130 +program_name$ +CHR$135,-1,5)
 2140 PROCcentre ("The Buggy will search its",12)
 2150 PROCcentre ("territory for an object,",14)
 2160 PROCcentre ("map it, and return home.",16)
 2170 PROCspace  ( 21 )
 2180 ENDPROC
 2190 DEF PROCmenu
 2200 CLS
 2210 PRINT TAB(0,1) CHR$130 +"BBC Buggy"
 2220 PRINT TAB(7,10) "1. " +program_name$ +"."
 2230 PRINT TAB(7,12) "2. Exit program."
 2240 PRINT TAB(3,20) "Your choice: ";
 2250 option = VAL( FNinput (1,"12"))
 2260 ENDPROC
 2270 :
 2280 DEF PROCscale
 2290 scale = 10
 2300 Xscale = scale * Xfactor
 2310 VDU 19,1,7;0;   :REM white foreground
 2320 VDU 19,0,1;0;   :REM red background
 2330 CLS
 2340 PROCcentre ("Put Buggy as shown in corner of area;",2)
 2350 PROCcentre (" centre of track 14 cms from the edh flag
 2750 off_screen  = FALSE :REM Out-of-limits flag
 2760 ENDPROC
 2770 :
 2780 REM UNIVERSAL BUGGY PROCEDURES
 2790 DEF PROCboundary (X1,Y1,X2,Y2)
 2800 X1 = X1 * Xscale
 2810 X2 = X2 * Xscale
 2820 Y1 = Y1 *  scale
 2830 Y2 = Y2 *  scale
 2840 PROCrectangle (X1,Y1,X2,Y2)
 2850 VDU 24,X1;Y1;X2;Y2;      :REM Graphics window
 2860 ENDPROC
 2870 :
 2880 DEF PROCbug
 2890 PROCdrawbug
 2900 PROCcalcpos
 2910 PROCcalcbug (GRX,GRY,angle)
 2920 PROCdrawbug
 2930 IF FNlimit (BGX,BGY,BF,BF,horiz-BF,vert-BF) THEN PROCwarn ("The Buggy is going off the screen!") :hit = 1 :off_screen = TRUE ELSE PROCcentre ("Press ESCAPE to exit program",4)
 2940 ENDPROC
 2950 :
 2960 DEF PROCcalcbug (X,Y,angle)
 2970 REM Accesses BF,BR,CW,BW,scale,Xscale
 2980 REM Alters Buggy screen co-ordinates
 2990 LOCAL SN,CS,leftoffset,rightoffset,frontoffset,rearoffset
 3000 frontoffset = RAD  angle
 3010 rearoffset  = RAD (angle-180)
 3020 leftoffset  = RAD (angle- 90)
 3030 rightoffset = RAD (angle+ 90)
 3040 REM Front middle of bumpers
 3050 FMX = X + BF * SIN frontoffset * Xscale
 3060 FMY = Y + BF * COS frontoffset * scale
 3070 REM Rear middle of chassis
 3080 RMX = X + BR * SIN rearoffset * Xscale
 3090 RMY = Y + BR * COS rearoffset * scale
 3100 REM Left side of buggy
 3110 SN = SIN leftoffset * Xscale
 3120 CS = COS leftoffset * scale
 3130 REM Left bumper
 3140 LBX = FMX + BW * SN
 3150 LBY = FMY + BW * CS
 3160 REM Front left corner
 3170 FLX = FMX + CW * SN
 3180 FLY = FMY + CW * CS
 3190 REM Rear left corner
 3200 RLX = RMX + CW * SN
 3210 RLY = RMY + CW * CS
 3220 REM Right side of buggy
 3230 SN = SIN rightoffset * Xscale
 3240 CS = COS rightoffset * scale
 3250 REM Right bumper
 3260 RBX = FMX + BW * SN
 3270 RBY = FMY + BW * CS
 3280 REM Front right corner
 3290 FRX = FMX + CW * SN
 3300 FRY = FMY + CW * CS
 3310 REM Rear right corner
 3320 RRX = RMX + CW * SN
 3330 RRY = RMY + CW * CS
 3340 ENDPROC
 3350 :
 3360 DEF PROCcalcpos
 3370 REM Updates Buggy co-ordinates
 3380 LOCAL A
 3390 angle = angle + turn
 3400 A = RAD angle
 3410 BGX = BGX + distance * FWD * SIN A
 3420 BGY = BGY + distance * FWD * COS A
 3430 GRX = BGX * Xscale
 3440 GRY = BGY * scale
 3450 distance = 0
 3460 turn = 0
 3470 ENDPROC
 3480 :
 3490 DEF PROCcrash (bumper)
 3500 IF (bumper AND  leftbumper)<>0 THEN MOVE LBX,LBY:PLOT 6,FMX,FMY:hit = -1
 3510 IF (bumper AND rightbumper)<>0 THEN MOVE RBX,RBY:PLOT 6,FMX,FMY:hit =  1
 3520  SOUND 0,-15,9+hit,4        :REM Different sound for each bumper
 3530 VDU 29,0;0;                :REM Graphics origin
 3540 VDU 24,510;220;800;700;    :REM Graphics window
 3550 MOVE 510,270 : MOVE 580,270
 3560 PLOT 86+hit,580,220        :REM Only the relevant triangle is filled
 3570 MOVE 730,270 : MOVE 800,270
 3580 PLOT 86-hit,730,220
 3590 VDU 29,640-horiz DIV 2 * Xscale;320;:REM Graphics origin
 3600 PROCboundary (0,0,horiz,vert)
 3610 PROCmove_bug (backwards,safedistance,nosensors)
 3620 VDU 29,0;0;                :REM Graphics origin
 3630 VDU 24,510;220;800;700;    :REM Graphics window
 3640 MOVE 510,270 : MOVE 580,270
 3650 PLOT 87,580,220            :REM Delete both triangles
 3660 MOVE 730,270 : MOVE 800,270
 3670 PLOT 87,730,220
 3680 VDU 29,640-horiz DIV 2 * Xscale;320;:REM Graphics origin
 3690 PROCboundary (0,0,horiz,vert)
 3700 ENDPROC
 3710 :
 3720 DEF PROCdrawbug
 3730 REM Ensures good corners at rear
 3740 MOVE    LBX,LBY
 3750 PLOT  6,RBX,RBY
 3760 MOVE    RLX,RLY
 3770 PLOT 30,FLX,FLY
 3780 MOVE    RLX,RLY
 3790 PLOT 30,RRX,RRY
 3800 PLOT 30,FRX,FRY
 3810 PLOT 70,RLX,RLY
 3820 ENDPROC
 3830 :
 3840 DEF PROCend
 3850 REM Switches motors off, resets cursor, EDIT & ESCAPE keys, buffers, and PRINT format
 3860 PROCmotors_off
 3870 PROCon
 3880 *FX 4
 3890 *FX 229
 3900 *FX 15
 3910 @% = 10
 3920 ENDPROC
 3930 :
 3940 DEF PROCmotors_off
 3950 ?port = 8
 3960 ENDPROC
 3970 :
 3980 DEF PROCmotors_on
 3990 ?port = 0
 4000 ENDPROC
 4010 :
 4020 DEF PROCmove_bug (direction,move,sensors)
 4030 LOCAL count
 4040 count = 0
 4050 hit = 0
 4060 REPEAT
 4070 count = count + 1
 4080 ?port = direction     :PROCdelay (speedcontrol)
 4090 ?port = direction OR 2:PROCdelay (speedcontrol)
 4100 hit = (?port AND sensors)
 4110 UNTIL hit OR count>=move
 4120 ?port=0
 4130 IF direction = left      THEN turn     = turn     - count
 4140 IF direction = right     THEN turn     = turn     + count
 4150 IF direction = backwards THEN distance = distance - count
 4160 IF direction = forwards  THEN distance = distance + count
 4170 PROCbug
 4180 PROCupdate
 4190 ENDPROC
 4200 :
 4210 DEF PROCnogo
 4220 PROCcentre ("Buggy not connected, END OF PROGRAM.",21)
 4230 PRINT
 4240 ENDPROC
 4250 :
 4260 DEF PROCscreen
 4270 REM "Instrument panel"
 4280 VDU 28,0,30,39,24     :REM Text window
 4290 CLS
 4300 RESTORE
 4310 FOR index = 1 TO 14
 4320 READ M1,M2,D1,D2
 4330 MOVE M1,M2
 4340 DRAW D1,D2
 4350 NEXT index
 4360 PRINT TAB(6,0)  "Position"
 4370 PRINT TAB(19,0) "Deg"
 4380 DATA    6, 280,1270, 280,       6, 210, 500, 210,     590, 210, 720, 210
 4390 DATA  810, 210,1010, 210,       6, 140,1270, 140,    1070, 210,1270, 210
 4400 DATA  150, 280, 150, 140,     500, 280, 500, 140,      590, 280, 590, 140
 4410 DATA  720, 280, 720, 140,     810, 280, 810, 140,     1010, 280,1010, 140
 4420 DATA 1070, 280,1070, 140,    1170, 280,1170, 210
 4430 PROCedge
 4440 ENDPROC
 4450 :
 4460 DEF PROCsetup_general
 4470 REM Buggy dimensions are in centimetres
 4480 BF  = 3.9    :REM Buggy centre to bumper
 4490 BR  = 9      :REM Buggy centre to chassis rear
 4500 CW  = 6      :REM Half chassis width
 4510 BW  = 9      :REM Bumper width (1 side)
 4520 FWD = 0.1431944:REM Travel (cms/pulse)
 4530 safedistance = ( INT( SQR( BR*BR + CW*CW ) -BF )) / FWD +14
 4540 REM Values to compare with port
 4550 bumpers       = 192
 4560 leftbumper    = 128
 4570 rightbumper   = 64
 4580 nosensors     = 0
 4590 REM Keyboard control words
 4600 uparrow       = -58
 4610 downarrow     = -42
 4620 leftarrow     = -26
 4630 rightarrow    = -122
 4640 space         = -99
 4650 nokey         = -129
 4660 escape        = -113
 4670 REM Port values for Buggy movement
 4680 forwards      = 0
 4690 backwards     = 5
 4700 left          = 4
 4710 right         = 1
 4720 digit$ = "1234567890"  :REM Acceptable characters for numeric input
 4730 space$ = STRING$(36," ")
 4740 @%     = &303          :REM Print format
 4750 ENVELOPE 3,1,5,-5,5,10,10,10,5,0,-1,-1,126,0
 4760 ENDPROC
 4770 :
 4780 DEF PROCupdate
 4790 PRINT TAB(6,2) INT(BGX+0.5) "," INT(BGY+0.5)
 4800 angle = (360+angle) MOD 360
 4810 PRINT TAB(19,2) angle
 4820 ENDPROC
 4830 :
 4840 DEF PROCwarn (text$)
 4850 PROCcentre (text$,4)
 4860 SOUND &103,3,100,10
 4870 SOUND &102,3,117,10
 4880 ENDPROC
 4890 :
 4900 REM UTILITIES
 4910 DEF PROCcentre(t$,l):PRINT TAB(1,l)SPC38:PRINT TAB(FNcentre(t$),l)t$;:ENDPROC
 4920 DEF FNcentre(t$)=19-LEN(t$)DIV2
 4930 DEF PROCcomplete:CLS:PROCdouble(CHR$131+"Mission completed.",-1,10):PROCend:ENDPROC
 4940 DEF PROCdelay(p):LOCAL i:FOR i=1TO p:NEXT:ENDPROC
 4950 DEF PROCdouble(t$,X,Y):IF X<0 THEN X=FNcentre(t$)
 4960 PRINT TAB(X-1,Y)CHR$141;t$;TAB(X-1,Y+1)CHR$141;t$:ENDPROC
 4970 DEF PROCedge:PROCrectangle(6,6,1274,1018):ENDPROC
 4980 :
 4990 DEF FNinput(l,a$):LOCAL i$,c
 5000 PRINT STRING$(l,".");STRING$(l,CHR$8);:PROCon:*FX 15
 5010 REPEAT:c=ASC FNwait:IF c=127 AND LEN(i$)>0 THEN i$=LEFT$(i$,LEN(i$)-1):VDU c
 5020 IF INSTR(a$,CHR$ c) AND LEN(i$)<l THEN i$=i$+CHR$ c ELSE IF c<>13 AND c<>127 THEN c=7
 5030 IF c=13 AND LEN(i$)<1 THEN c=7
 5040 IF c=127 THEN VDU46,8 ELSE VDU c
 5050 UNTIL c=13:PRINT:PROCoff
 5060 =i$
 5070 DEF FNlimit(X,Y,X1,Y1,X2,Y2):IF X>X1 AND X<X2 AND Y>Y1 AND Y<Y2 THEN =FALSE ELSE =TRUE
 5080 DEF FNmax(A,B):IF A>B THEN=A ELSE=B
 5090 DEF FNmin(A,B):IF A<B THEN=A ELSE=B
 5100 DEF PROCoff VDU 23;11,0;0;0;0:ENDPROC
 5110 DEF PROCon  VDU 23;11,255;0;0;0:ENDPROC
 5120 DEF PROCrectangle(X1,Y1,X2,Y2):MOVEX1,Y1:DRAW X1,Y2:DRAW X2,Y2:DRAW X2,Y1:DRAW X1,Y1:ENDPROC
 5130 DEF PROCspace(l):LOCAL I$:PROCcentre("Press the SPACE bar to continue.",l):REPEAT I$=FNwait:UNTIL INKEY (space) OR INKEY (escape):ENDPROC
 5140 :
 5150 DEF FNwait
 5160 LOCAL I$
 5170 *FX 4,1
 5180 REPEAT
 5190 I$=INKEY$(10000)
 5200 IF I$="" THEN PROCmotors_off ELSE PROCmotors_on
 5210 UNTIL I$<>""
 5220 *FX 4
 5230 =I$
 5240 :