10 REM Vader's Last Stand
20 REM By Jason H. Moore, Ph.D.
30 REM December 21, 2019
40 REM A mini-game programmed in BASIC XE
50 REM to illustrate and teach Atari graphics.
60 REM For educational and instructional purposes only.
70 REM This version has minimal comments.

100 REM ***************************************
101 REM *** EXECUTE INITIALIZATION ROUTINES ***
102 REM ***************************************

110 FAST:REM      Precompiles the line numbers for speed
120 POKE 77,0:REM Turn off screen saver

130 GOSUB 4000:REM Setup graphics & title screen
140 GOSUB 5000:REM Move & redefine character set
150 GOSUB 6000:REM Set up game variables
160 GOSUB 7000:REM Draw playfield
170 GOSUB 8000:REM Setup PM graphics

500 REM *****************
501 REM *** MAIN LOOP ***
502 REM *****************

510 REM CHECK JOYSTICK, MOVE PLAYER & MISSILES

520 GOSUB 600
530 GOSUB 700
540 GOTO 520
550 END

600 REM PLAYER & MISSILE MOVEMENT 

610 P0VS=VSTICK(0)*PSPEED:P0HS=HSTICK(0)*PSPEED
620 P0X=P0X+P0HS
630 PMMOVE 0,P0X;P0VS
640 PMMOVE 6,M2X
650 PMMOVE 7,M3X
660 RETURN

700 REM MISSILE MOVEMENT CALCULATIONS AND DIFFICULTY

710 IF MNEW=0 THEN GOTO 1600
720 PMCLR 4
730 M2Y=INT(RND(1)*140+50):M3Y=INT(RND(1)*140+50)
740 M2SIDE=RND(1):M3SIDE=RND(1)
750 M2X=(M2SIDE<=0.5)*30+(M2SIDE>0.5)*220
760 M3X=(M3SIDE<=0.5)*30+(M3SIDE>0.5)*220
770 MISSILE 2,M2Y,4:MISSILE 3,M3Y,4
780 SOUND 0,225,6,255:SOUND 0,150,6,255:SOUND 0,75,6,255
790 SOUND 0,0,0,0

1000 REM INCREASE DIFFICULTY AS SCORE INCREASES

1010 SCORE=SCORE+1
1020 POKE 87,1:POSITION 6,0:PRINT #6;SCORE
1030 MNEW=0

1040 IF SCORE>5 THEN GOTO 1100
1050 MSPEED=2
1060 GOTO 1600

1100 IF SCORE>10 THEN GOTO 1200
1110 MSPEED=3
1120 GOTO 1600

1200 IF SCORE>15 THEN GOTO 1300
1210 MSPEED=4
1220 POKE 87,2:POSITION 10,7:PRINT #6; "*"
1230 GOTO 1600

1300 IF SCORE>20 THEN GOTO 1400
1310 MSPEED=4
1320 POKE 87,2:POSITION 6,8:PRINT #6; "*"
1330 GOTO 1600

1400 IF SCORE>30 THEN GOTO 1500
1410 MSPEED=5
1420 POKE 87,2:POSITION 8,3:PRINT #6; "*"
1430 GOTO 1600

1500 MSPEED=6
1510 POKE 87,2:POSITION 12,5:PRINT #6; "*"

1600 REM SET NEW MISSILE X POSITIONS

1610 M2X=M2X+MSPEED*((M2SIDE<=0.5)-(M2SIDE>0.5))
1620 M3X=M3X+MSPEED*((M3SIDE<=0.5)-(M3SIDE>0.5))
1630 MNEW=((M2X<30)+(M2X>220))

1700 REM CHECK FOR COLLISIONS

1710 IF BUMP(6,0)=1 THEN GOTO 3000
1720 IF BUMP(7,0)=1 THEN GOTO 3000
1730 IF BUMP(0,8)=1 THEN GOTO 3000
1740 RETURN

3000 REM COLLISION, END THE GAME

3010 PMCLR 4
3020 FOR I=1 TO 15
3030 SOUND 0,250,4,15/I+5
3040 POKE 704,64+I
3050 FOR J=1 TO 100
3060 NEXT J
3070 NEXT I
3080 PMCLR 0
3090 SOUND 0,0,0,0

3100 FOR I=1 to 1000:NEXT I
3110 PRINT #6;CHR$(125)
3120 SETCOLOR 0,4,10
3130 POKE 87,2:POSITION 2,4:PRINT #6;"FINAL SCORE "
3140 POSITION 14,4:PRINT #6;SCORE
3150 POSITION 2,6:PRINT #6;"PRESS START"
3160 IF PEEK(53279)=6 THEN RUN
3170 GOTO 3160

4000 REM **************************************
4001 REM *** SET UP GRAPHICS & TITLE SCREEN ***
4002 REM **************************************

4010 GRAPHICS 2+16:POKE 752,1
4020 DL=PEEK(560)+PEEK(561)*256+4
4030 POKE DL-1,70
4040 SETCOLOR 0,12,8:SETCOLOR 2,0,0

4100 POKE 87,2
4110 POSITION 2,2:PRINT #6; "    VADER'S"
4120 POSITION 2,3:PRINT #6; "   LAST STAND"
4130 POSITION 2,5:PRINT #6; "       BY"
4140 POSITION 2,6:PRINT #6; " JASON H. MOORE"
4150 POSITION 2,9:PRINT #6; "   GET READY!"

4200 RETURN

5000 REM *************************************
5001 REM *** MOVE & REDEFINE CHARACTER SET ***
5002 REM *************************************

5010 MEMTOP=PEEK(106)
5020 CHADDR=(MEMTOP-8)*256
5030 CHROM=PEEK(756)*256
5040 MOVE CHROM,CHADDR,512

5100 REM REDEFINE CHARS # (3) TO ) (9)
5110 REM THEN + (11) to / (15) AND : (26) to = (29)
5120 REM SKIPPING * AND NUMBERS SO WE CAN USE THEM

5130 CHRAM=CHADDR+24:REM Start with #
5140 FOR I=1 to 7
5150 FOR ADDR=CHRAM TO CHRAM+7
5160 READ DAT:POKE ADDR,DAT
5170 NEXT ADDR
5180 CHRAM=CHRAM+8
5190 NEXT I

5200 CHRAM=CHRAM+8:REM Start with +, skip *
5210 FOR I=1 to 5
5220 FOR ADDR=CHRAM TO CHRAM+7
5230 READ DAT:POKE ADDR,DAT
5240 NEXT ADDR
5250 CHRAM=CHRAM+8
5260 NEXT I

5300 CHRAM=CHRAM+80:REM Now do : to @
5310 FOR I=1 to 7
5320 FOR ADDR=CHRAM TO CHRAM+7
5330 READ DAT:POKE ADDR,DAT
5340 NEXT ADDR
5350 CHRAM=CHRAM+8
5360 NEXT I

5400 CHRAM=CHRAM+208:REM Now do [ to _
5410 FOR I=1 to 5
5420 FOR ADDR=CHRAM TO CHRAM+7
5430 READ DAT:POKE ADDR,DAT
5440 NEXT ADDR
5450 CHRAM=CHRAM+8
5460 NEXT I

5500 RETURN

6000 REM ****************************
6001 REM *** SETUP GAME VARIABLES ***
6002 REM ****************************

6010 P0X=120:P0Y=120
6020 PSPEED=2:MSPEED=2
6030 MNEW=1
6040 SCORE=0

6100 RETURN

7000 REM **************************
7001 REM *** DRAW THE PLAYFIELD ***
7002 REM **************************

7010 PRINT #6;CHR$(125)
7020 POKE 756,CHADDR/256
7030 SETCOLOR 0,0,8

7040 POKE 87,1
7050 POSITION 0,0:PRINT #6; "SCORE 0"

7100 REM Draw Death Star

7110 POKE 87,2
7120 POSITION 3,2:PRINT #6;"#',:"
7130 POSITION 3,3:PRINT #6;"$(-;"
7140 POSITION 3,4:PRINT #6;"%).<"
7150 POSITION 3,5:PRINT #6;"&+/="

7200 REM Draw Mines

7210 POSITION 1,2:PRINT #6; "*"
7220 POSITION 12,2:PRINT #6; "*"
7230 POSITION 2,8:PRINT #6; "*"
7240 POSITION 14,9:PRINT #6; "*"
7250 POSITION 16,5:PRINT #6; "*"

7300 REM Draw Border

7310 POSITION 0,1:PRINT #6; "\"
7320 POSITION 19,1:PRINT #6; "]"
7330 POSITION 0,10:PRINT #6; "^"
7340 POSITION 19,10:PRINT #6; "_"

7350 POSITION 1,1:PRINT #6; ">>>>>>>>>>>>>>>>>>"
7360 POSITION 1,10:PRINT #6; "??????????????????"
7370 FOR I=2 TO 9
7380 POSITION 0,I:PRINT #6;"@"
7390 POSITION 19,I:PRINT #6;"["
7400 NEXT I

7500 RETURN

8000 REM *************************************
8001 REM *** SETUP PLAYER MISSILE GRAPHICS ***
8002 REM *************************************

8010 PMGRAPHICS 1
8020 PMCLR 0:PMCLR 4
8030 PMWIDTH 0,2:PMWIDTH 6,3:PMWIDTH 7,3
8040 PMCOLOR 0,12,12:PMCOLOR 2,2,12:PMCOLOR 3,2,12
8050 P0ADR=PMADR(0)

8100 REM Load player 0 shape data into memory

8110 FOR I=P0ADR+P0Y TO P0ADR+P0Y+13
8120 READ DAT:POKE I,DAT
8130 NEXT I

8500 RETURN

10000 REM **************************************
10001 REM *** DATA FOR DEATH STAR CHARACTERS ***
10002 REM **************************************

10010 DATA 0,0,3,7,15,15,31,31
10020 DATA 63,63,127,127,127,127,127,127
10030 DATA 0,127,127,127,127,127,63,63
10040 DATA 31,31,15,15,7,1,0,0
10050 DATA 0,63,255,255,255,255,255,207
10060 DATA 135,3,3,135,207,255,255,255
10070 DATA 0,255,255,255,255,255,255,255
10080 DATA 255,255,255,255,255,255,63,0
10090 DATA 0,252,255,255,255,255,255,255
10100 DATA 255,255,255,255,255,255,255,255
10110 DATA 0,255,255,255,255,255,255,255
10120 DATA 255,255,255,255,255,255,252,0
10130 DATA 0,0,128,224,240,240,248,248
10140 DATA 252,252,254,254,254,254,254,254
10150 DATA 0,254,254,254,254,254,252,252
10160 DATA 248,248,240,240,224,128,0,0

11000 REM ***********************************
11001 REM *** DATA FOR BORDER AND CORNERS ***
11002 REM ***********************************

11010 DATA 255,255,255,0,0,0,0,0
11020 DATA 0,0,0,0,0,255,255,255
11030 DATA 224,224,224,224,224,224,224,224
11040 DATA 7,7,7,7,7,7,7,7
11050 DATA 255,255,255,224,224,224,224,224
11060 DATA 255,255,255,7,7,7,7,7
11070 DATA 224,224,224,224,224,255,255,255
11080 DATA 7,7,7,7,7,255,255,255

12000 REM ****************************
12001 REM *** DATA FOR TIE FIGHTER ***
12002 REM ****************************

12010 DATA 66,129,129,153,153,255,255
12020 DATA 255,255,153,153,129,129,66