M.A.C.E. Journal / VOL. 5 NO.6 / JUNE 1985 / PAGE 39

AMAZED

by Patrick Steele

Maze games have been around for a while. So when you see another maze game, you don’t think much of it. Well, I’m going to try to change that.

When Amazed is run, a maze in graphics 7 will be drawn. You are then ‘shrunk’ to fit inside the maze. At this reduced size, everything is much bigger, EVEN THE MAZE WALLS. The maze has been divided into 16 Graphics 3 screens. That’s rights you can only see one sixteenth of the maze at a time!

Using joystick number 1, move yourself (the green dot) around the maze, trying to find the exit (a blue dot). You start at the upper left hand corner and must get to the lower right hand corner. The screen scrolls independently of you. This may seem an annoyance, because you may hit a wall but the screen will continue scrolling, but I did this so you can see how far you are from the exit at any time. Just move all the way to the lower right hand corner and you will see the blue dot. Just remember where you were when you started scrolling the screen around.

I am an 18 year old senior at Warren Woods Tower High school. I’ve known assembly language for a couple of years now and enjoy the increase in speed from BASIC. This program took about 3 weeks to do. The hardest part was the fine scrolling routines. If anybody has any questions about this program, leave a message to ‘Remington Steele’, at the Trading Post BBS (882-5909) or the MACE EAST BBS (978-1685).

Enjoy the mazes and have fun!!

[The following listing is the source code for the machine language program. The assembled version of Amazed will be available from the MACE disk library and on the MACE BBSs. -Ed.]

0100 WSYNC=54282     ;wait for horiz. sync.
0110 COLPF0=53270    ;color 0
0120 DLIST=560       ;display list pointer
0130 DISP=$5000      ;screen display RAM
0140 RANDOM=53770    ;random #
0150 SETVBI=$E45C    ;set VBI vector
0160 RETURN=$E462    ;ret. from vbi
0170 HSCROLL=54276   ;horiz. scroll
0180 VSCROLL=54277   ;vert. scroll
0190 STICK=632       ;stick 0
0200 TIMER=540       ;countdown timer
0210 XPNT=$8000      ;x,y coordinate
0220 YPNT=$9000      ;save RAM
0230  *=$B0
0240 X *=*+1         ;misc.
0250 Y *=*+1         ;variables
0260 XP *=*+1
0279 YP *=*+1
0280 LO *=*+1        ;a lo and hi pntr.
0290 HI *=*+1
0300 DIR *=*+1       ;direction of movement
0310 LOHOLD *=*+1    ;temporary hold
0320 HIHOLD *=*+1    ;registers
0330 XPOINT *=*+2
0340 YPOINT *=*+2
0350 Z1 *=*+1        ;used for the LOCATE
0360 Z2 *=*+1        ;of the four points which
0370 Z3 *=*+1        ;surround the current
0380 Z4 *=*+1        ;x,y point
0390 HS *=*+1        ;horiz. scroll value
0400 VS *=*+1        ;vert. scroll value
0410 HD *=*+1
0420 VD *=*+1
0430 OX *=*+1
0440 OY *=*+1
0450  *=$600
0460 ;
0470 ; masks for plotting
0480 ;
0490 COLOR0
0500  .BYTE $3F,$CF,$F3,$FC
0510 COLOR1
0520  .BYTE $40,$10,$04,$01
0530 COLOR2
0540  .BYTE $80,$20,$08,$02
0550 COLOR3
0560  .BYTE $C0,$30,$0C,$03
0561 ;
0562 ; mask bits for locate
0563 ;
0570 TEST
0580  .BYTE $C0,$30,$0C,$03
0581 ;
0582 ; GR.7 display list
0583 ;
0590 LIST
0600  .BYTE 112,112,112,77
0610  .WORD DISP
0620  .BYTE 13,13,13,13,13,13,13,13
0630  .BYTE 13,13,13,13,13,13,13,13
0640  .BYTE 13,13,13,13,13,13,13,13
0650  .BYTE 13,13,13,13,13,13,13,13
0660  .BYTE 13,13,13,13,13,13,13,13
0670  .BYTE 13,13,13,13,13,13,13,13
0680  .BYTE 13,13,13,13,13,13,13,13
0699  .BYTE 13,13,13,13,13,13,13,13
0700  .BYTE 13,13,13,13,13,13,13,13
0710  .BYTE 13,13,13,13,13,13,13,13
0720  .BYTE 13,13,13,13,13,13,13,13
0730  .BYTE 13,13,13,13,13,13,13,65
0740  .WORD LIST
0750 GR3LIST
0760  .BYTE 112,112,112
0770  .BYTE 120,0,0,120,0,0,120,0,0
0780  .BYTE 120,0,0,120,0,0,120,0,0
0790  .BYTE 120,0,0,120,0,0,120,0,0
0800  .BYTE 120,0,0,120,0,0,120,0,0
0810  .BYTE 120,0,0,120,0,0,120,0,0
0820  .BYTE 120,0,0,120,0,0,120,0,0
0830  .BYTE 120,0,0,120,0,0,120,0,0
0840  .BYTE 120,0,0,120,0,0,120,0,0
0850  .BYTE 65
0860  .WORD GR3LIST
0861 ;
0862 ; x,y increments for joystick
0863 ; movement
0864 ;
0870 XI
0880  .BYTE 0,0,0,0,0,0,0,1,0,0
0890  .BYTE 0,255,0,0,0,0
0900 YI
0910  .BYTE 0,0,0,0,0,0,0,0,0,0,0
0920  .BYTE 0,0,1,255,0
0930  *=$6000
0940  JMP START
0941 ;
0942 ; area for saving the addr of each
0943 ; line of the gr.7 display
0944 ;
0950 LMSLO *=*+95
0960 LMSHI *=*+95
0961 ;
0962 ; plot calculator:
0963 ; multiply YP times 40 then get the
0964 ; addr of the screen RAM to be
0965 ; modified.
0966 ;
0970 PLOTCL
0980  LDA YP
0990  ASL A
1000  STA LO
1010  LDA #0
1020  STA HI         ;*2
1030  ASL LO
1040  ROL HI         ;*4
1050  ASL LO
1060  ROL HI         ;*8
1070  LDA LO
1080  STA LOHOLD
1090  LDA HI
1100  STA HIHOLD
1110  ASL LO
1120  ROL HI         ;*16
1130  ASL LO
1140  ROL HI         ;*32
1150  LDA LO
1160  CLC
1170  ADC LOHOLD
1180  STA LO
1190  LDA HI
1200  ADC HIHOLD
1210  STA HI         ;*32+*8=*40
1220  LDA LO         ;add offset for
1230  CLC            ;the screen RAH
1240  ADC #DISP&255
1250  STA LO
1260  LDA HI
1270  ADC #DISP/256
1280  STA HI
1290  LDA XP         ;mask x-pos.
1300  AND #3
1310  TAX
1320  LDA XP
1330  LSR A
1340  LSR A
1350  CLC
1360  ADC LO
1370  STA LO
1380  LDA HI
1390  ADC #0
1400  STA HI
1410  RTS ;all done!
1420 PLOT0
1430  LDA X ;save x,y pos.
1440  STA XP
1450  LDA Y
1460  STA YP
1470 P0
1480  JSR PLOTCL
1490  LDA COLOR0,X ;plot a point in
1500  LDY #0     ;color 0
1510  AND (LO),Y
1520  STA (LO),Y
1530  RTS ;all done!
1540 XYUPDATE
1550  LDY #0 ;update the x,y
1560  LDA X ;pointers in RAM
1570  STA (XPOINT),Y
1580  LDA Y
1590  STA (YPOINT),Y
1600  LDA XPOINT
1610  CLC
1620  ADC #1
1630  STA XPOINT
1640  LDA XPOINT+1
1650  ADC #0
1660  STA XPOINT+1
1670  LDA YPOINT
1680  CLC
1690  ADC #1
1700  STA YPOINT
1710  LDA YPOINT+1
1720  ADC #0
1730  STA YPOINT+1
1740  RTS
1750 NEWXY
1760  LDA XPOINT ;get a new x,y
1770  SEC       ;position after
1780  SBC #1 ;it has been determined
1790  STA XPOINT ;that the current
1800  LDA XPOINT+1 ;x,y point has no where
1810  SBC #0 ;to go, but in reverse!
1820  STA XPOINT+1
1830  LDA YPOINT
1840  SEC
1850  SBC #1
1860  STA YPOINT
1870  LDA YPOINT+1
1880  SBC #0
1890  STA YPOINT+1
1900  LDY #0
1910  LDA (XPOINT),Y
1920  STA X
1930  LDA (YPOINT),Y
1940  STA Y
1950  LDA X          ;is x=2
1960  CMP #2
1970  BNE NOTDONE
1980  LDA Y          ;and y=2
1990  CMP #2
2000  BNE NOTDONE
2010  PLA            ;then we are all
2020  PLA            ;done drawing!!
2030  JMP LOADLMS
2040 NOTDONE
2050   RTS           ;do some more mazing !
2060 LOCATE
2070  LDY #0
2080  LDA TEST,X     ;get the test bit
2090  AND (LO),Y     ;mask it with current x,y pos.
2100  CMP COLOR1,X   ;is it color 1
2110  BNE COL0
2120  LDA #1         ;yes!
2130  RTS
2140 COL0
2150  LDA #0         ;it must be color 0
2160  RTS
2170 START
2180  LDA #0         ;set horiz. and vert.
2190  STA VS         ;scroll regs. to 0
2200  STA HD
2210  STA VD
2220  LDA #15
2230  STA HS
2240  LDA #XPNT&255  ;set the x,y
2250  STA XPOINT     ;table pointers
2260  LDA #XPNT/256
2270  STA XPOINT+1
2280  LDA #YPNT&255
2290  STA YPOINT
2300  LDA #YPNT/256
2310  STA YPOINT+1
2320  LDA #LIST&255  ;point to. display
2330  STA DLIST      ;list
2340  LDA #LIST/256
2350  STA DLIST+1
2360 CLEARSCRN
2370  LDA #0         ;start at x=0
2380  STA XP
2390  LDA #95        ;and y=95
2400  STA YP
2410 CLEAR
2420  JSR PLOTCL     ;get addr. of line
2430  LDA #0         ;and clear out
2440  LDY #39        ;all 40 bytes in
2450 CLR             ;it
2460  STA (LO),Y
2470  DEY            ;loop..
2480  BPL CLR
2490  DEC YP
2500  LDA YP
2510  CMP #$FF
2520  BNE CLEAR      ;until done
2530  LDA #1
2540  STA YP
2550  LDA #0
2560  STA XP
2570 FIELD
2580  JSR PLOTCL     ;draw out the
2590  LDA #21        ;field on which
2600  LDY #0         ;the maze will be
2610  STA (LO),Y     ;drawn
2620  LDA #80
2630  LDY #39
2640  STA (LO),Y
2650  LDY #1
2660  LDA #85
2670 DRAW
2680  STA (LO),Y
2690  INY
2700  CPY #39
2710  BNE DRAW
2720  INC YP
2730  LDA yp
2740  CMP #94
2750  BNE FIELD
2760 MAZE
2770  LDA #2         ;start at 2,2
2780  STA X
2790  STA Y
2800 MOVE
2810  JSR XYUPDATE   ;and save those points
2820 GETZ
2830  JSR PLOT0      ;plot, color 0
2840  LDX Y          ;now locate
2850  DEX            ;the four points
2860  DEX            ;around x,y
2870  STX YP
2880  LDA X
2890  STA XP
2900  JSR PLOTCL     ;this is the locate for...
2910  JSR LOCATE     ;x,y-2
2920  STA Z1
2930  LDA Y
2940  STA YP
2950  LDX X
2960  INX
2970  INX
2980  STX XP
2990  JSR PLOTCL
3000  JSR LOCATE
3010  STA Z2         ;x+2,y
3020  LDA X
3030  STA XP
3040  LDX Y
3050  INX
3060  INX
3070  STX YP
3080  JSR PLOTCL
3090  JSR LOCATE
3100  STA Z3         ;x,y+2
3110  LDA Y
3120  STA YP
3130  LDX X
3140  DEX
3150  DEX
3160  STX XP
3170  JSR PLOTCL
3180  JSR LOCATE
3190  STA Z4         ;x-2,y
3200  LDA #0         ;add them all up
3210  CLC
3220  ADC Z1
3230  ADC Z2
3240  ADC Z3
3250  ADC Z4
3260  BNE GETDIR     ;if its not zero then maze!!
3270  JSR NEWXY      ;else, get a new x,y
3280  JMP GETZ       ;and start checking again
3290 GETDIR
3300  LDA RANDOM     ;get a rand.
3310  CMP #4         ;direction
3320  BCS GETDIR
3330  STA DIR        ;and save it.
3340  LDA DIR
3350  BNE NOT0       ;if dir=0
3360  LDA Z1         ;decrement y by
3370  BEQ GETDIR     ;2 and plot each
3330  DEC Y          ;point in color 0
3390  JSR PLOT0
3400  DEC Y
3410  JMP MOVE
3420 NOT0
3430  CMP #1         ;if dir=1
3440  BNE NOT1
3450  LDA Z2         ;and point.. if 0
3460  BEQ GETDIR
3470  INC X          ;increment x by
3480  JSR PLOT0      ;2
3490  INC X
3500  JMP MOVE
3510 NOT1
3520  CMP #2         ;if dir=2
3530  BNE NOT2
3540  LDA Z3         ;and point is 0
3550  BEQ GETDIR
3560  INC Y          ;inc. y by 2
3570  JSR PLOT0
3580  INC Y
3590  JMP MOVE
3600 NOT2
3610  CMP #3         ;if dir=3
3620  BNE OOPS
3630  LDA Z4         ;and point it 0
3640  BEQ GETDIR
3650  DEC X          ;dec. X by 2
3660  JSR PLOT0
3670  DEC X
3680  JMP MOVE
3690 OOPS
3700  LDA #15        ;this will never
3710  STA 708        ;happen!
3720  BRK
3730 LOADLMS
3740  LDA #0         ;xp=0 and yp=1
3750  STA XP
3760  LDA #1
3770  STA YP
3780 LMS
3790  JSR PLOTCL     ;find addr of RAM
3800  LDY YP
3810  DEY
3820  LDA LO         ;and save it
3830  STA LMSLO,Y
3840  LDA HI
3850  STA LMSHI,Y
3860  INC YP         ;get next line
3870  INY
3880  CPY #95        ;do al 95
3890  BNE LMS
3900  LDX #4
3910  LDY #0
3920 GETLMS
3930  LDA LMSLO,Y    ;put the current
3940  STA GR3LIST,X  ;pos. in the gr.3
3950  LDA LMSHI,Y    ;display list.
3960  STA GR3LIST+1,X
3970  INY
3980  INX
3990  INX
4000  INX
4010  CPX #76
4020  BNE GETLMS
4030  LDA #GR3LIST&255;point to gr.3
4040  STA DLIST      ;display
4050  LDA #GR3LIST/256
4060  STA DLIST+1
4070  LDA #7         ;set the vert.
4080  LDX #VBI/256   ;blank.
4090  LDY #VBI&255
4100  JSR SETVBI
4110  LDA #156       ;put a color 3
4120  STA XP         ;dot at the end
4130  LDA #92        ;of the maze.
4140  STA YP
4150  JSR PLOTCL     ;it'll be there
4160  LDY #0         ;if you ever get
4170  LDA COLOR3,X   ;there!
4180  ORA (LO),Y     ;ha!ha!ha!
4190  STA (LO),Y
4200  LDA #2         ;start your journey
4210  STA X          ;at 2.2
4220  STA Y
4230 PLXY
4240  LDA X          ; save x and y
4250  STA XP
4260  STA OX
4270  LDA Y
4280  STA YP
4290  STA OY
4300  JSR PLOTCL
4310  LDY #0
4320  LDA (LO),Y
4330  AND TEST,X     ;check if we hit
4340  CMP COLOR3,X   ;color 3
4350  BNE NOTCOL3    ;nope. keep trying!
4360  JMP WIN        ;FINALLY!!
4370 NOTCOL3
4380  LDA (LO),Y     ;plot x,y
4390  ORA COLOR2,X   ;in color 2
4400  STA (LO),Y
4410  LDA #2         ;a short delay
4420  STA TIMER
4430 WAIT
4440  LDA TIMER
4450  BNE WAIT
4460  LDX STICK      ;get stick dir.
4470  LDA XP
4480  CLC            ;and add it to
4490  ADC XI,X
4500  STA XP         ;the x and y
4510  LDA YP         ;pos.'s
4520  CLC
4530  ADC YI,X
4540  STA YP
4550  JSR PLOTCL     ;get addr.
4560  JSR LOCATE     ;check if 0
4570  BEQ XYOK       ;its ok to move there!
4580  JMP PLOTDONE   ;no movement.
4590 XYOK
4600  LDA XP         ;now actually move
4610  STA X          ;x and y points
4620  LDA YP
4630  STA Y
4640  LDA OX
4650  STA XP
4660  LDA OY
4670  STA YP
4680  JSR P0         ;erase old spot
4690 PLOTDONE
4700  JMP PLXY       ;keep looping.
4710 LOOP
4720  JMP LOOP
4730 VBI
4740  LDA STICK      ;moving right?
4750  CMP #7
4760  BNE CHK11      ;nope, check left
4770  LDA HS         ;if HS isnt 0,
4780  BEQ HS0
4790  DEC HS         ;we can dec. it
4800  JMP DONE
4810 HS0
4820  LDA HD         ;otherwise, if were
4830  CMP #29        ;not at the bottom
4840  BNE GO7        ;of the screen
4850  JMP DONE
4860 GO7
4870  INC HD
4880  LDA #15        ;reset the scroll
4890  STA HS         ;pointers and
4900  LDY #4
4910 ADD1
4920  LDA GR3LIST,Y  ;get the new memory
4930  CLC            ;address's for the
4940  ADC #1         ;gr.3 displat list
4950  STA GR3LIST,Y
4960  LDA GR3LIST+1,Y;move over 1 byte
4970  ADC #0
4980  STA GR3LIST+1,Y
4990  INY
5000  INY
5010  INY
5020  CPY #76        ;loop until done
5030  BNE ADD1
5040  JMP DONE
5050 CHK11
5060  CMP #11        ;moving left?
5070  BNE CHK13      ;no, try down
5080  LDA HS         ;can we move
5090  CMP #15        ;anymore??
5100  BEQ HS15
5110  INC HS         ;YEP!
5120  JMP DONE
5130 HS15
5140  LDA HD         ;check for
5150  BNE GO11       ;left edge of screen
5160  JMP DONE
5170 GO11
5180  DEC HD         ;reset the scroll
5190  LDA #0         ;registers
5200  STA HS
5210  LDY #4
5220 SUB1
5230  LDA GR3LIST,Y  ;and change the
5240  SEC            ;display
5250  SBC #1
5260  STA GR3LIST,Y  ;move back 1 byte
5270  LDA GR3LIST+1,Y
5280  SBC #0
5290  STA GR3LIST+1,Y
5300  INY 
5310  INY
5320  INY
5330  CPY #76
5340  BNE SUB1
5350  JMP DONE
5360 CHK13
5370  CMP #13        ;moving down??
5380  BNE CHK 14     ;no, check up
5390  LDA vs
5400  CMP #7         ;can we move down
5410  BEQ VS7
5420  INC VS         ;sure can!!
5430  JMP DONE
5440 VS7
5450  LDA VD         ;check for bottom
5460  CMP #70        ;of screen.
5470  BNE GO13
5480  JMP DONE
5490 GO13
5500  INC VD         ;reset the scroll
5510  LDA #0         ;registers
5520  STA VS
5530  LDY #4
5540 ADD40
5550  LDA GR3LIST,Y  ;and orange
5560  CLC            ;display list
5570  ADC #40
5580  STA GR3LIST,Y  ;move down 40 bytes,
5590  LDA GR3LIST+1,Y;or 1 gr.7 line
5600  ADC #0
5610  STA GR3LIST+1,Y
5620  INY
5630  INY
5640  INY
5650  CPY #76
5660  BNE ADD40
5670  JMP DONE
5680 CHK14
5690  CMP #14        ;moving up??
5700  BNE DONE       ;nopey all done.
5710  LDA VS
5720  BEQ VS0        ;can we move up?
5730  DEC VS         ;yep.
5740  JMP DONE
5750 VS0 
5760  LDA VD         ;are we at the to P?
5770  BEQ DONE       ;yes, dont move.
5780  DEC VD
5790  LDA #7         ;reset the scroll
5800  STA VS         ;registers
5810  LDY #4
5820 SUB40
5830  LDA GR3LIST,Y  ;and change the
5840  SEC            ;display list
5850  SBC #40
5860  STA GR3LIST,Y  ;move up 40 bytes
5870  LDA GR3LIST+1,Y;or 1 gr.7 line
5880  SBC #0
5890  STA GR3LIST+1,Y
5900  INY
5910  INY
5920  INY
5930  CPY #76
5940  BNE SUB40
5950 DONE
5960  LDA HS         ;update the scroll
5970  STA HSCROLL    ;registers
5980  LDA VS
5990  STA VSCROLL
6000  JMP RETURN     ;and finis!
6010 WIN
6020  INX            ;YEAH!! get a new color
6030  STX WSYNC      ;wait for sync.
6040  STX COLPF0     ;and display it.
6050  JMP WIN

7000  *=$02E0        ;autorun
7010  .WORD START
7020  .END