10 REM * DEMO OF PLAYER-MISSILE GRAPHICS USING THE VERTICAL *
20 REM * BLANK INTERRUPT FOR FAST PLAYER MOVEMENT           *
20 REM see CH5, p164 of Compute's First Book of Atari
30 REM for base code used to make this PM graphics demo
40 REM Modifications by Jason H. Moore, Ph.D.
50 REM March 25, 2019

100 REM * SET ASIDE MEMORY FOR PLAYER-MISSILE GRAPHICS * 
110 PM=PEEK(106)-16:REM FIND RAMTOP & SUBTRACT 16 PAGES
120 PMBASE=256*PM:REM BASE ADDRESS FOR PM GRAPHICS

200 REM * INITIALIZE GRAPHICS * 
210 GRAPHICS 0:SETCOLOR 2,0,0:REM BLACK BACKGROUND
220 POKE 752,1:PRINT " ":REM TURN OFF CURSOR
230 PCOL0=216:REM PLAYER COLOR GREEN
240 POKE 704,PCOL0:REM SET PLAYER COLOR

300 REM * INITIALIZE PLAYER POSITION MEMORY AND VARIABLES *
310 PXMEM=53248:PYMEM=1780:PHMEM=1784
320 P0X=120:P0Y=80

400 REM * INITIALIZE VBLANK PLAYER MOVEMENT ROUTINE *
410 FOR I=1536 TO 1706:READ A:POKE I,A:NEXT I
420 FOR I=1774 TO 1787:POKE I,0:NEXT I
430 FOR I=PMBASE+1023 TO PMBASE+2047:POKE I,0:NEXT I
440 FOR I=PMBASE+1025 TO PMBASE+1038:READ A:POKE I,A:NEXT I
450 POKE 559,62:POKE 623,1:POKE 1788,PM+4
460 POKE 53277,3:POKE 53256,1:POKE 54279,PM
470 X=USR(1696)

500 REM * GENERATE A TITLE *
510 POSITION 5,0
520 PRINT "PLAYER-MISSILE GRAPHICS DEMO"

600 REM * MAIN LOOP                      *
610 REM * SET PLAYER POSITION AND HEIGHT *
620 POKE PHMEM,14:REM HEIGHT
630 POKE PXMEM,P0X:POKE PYMEM,P0Y:REM POSITION
640 GOSUB 700
650 GOTO 620
660 END

700 REM * PLAYER MOVEMENT CALCULATIONS *
710 JOY = STICK(0):REM READ JOYSTICK VALUE
720 IF JOY=15 THEN RETURN:REM RETURN IF NOT PRESSED
730 IF JOY=11 THEN P0X=P0X-2:REM LEFT? DECREASE X
740 IF JOY=7 THEN P0X=P0X+2:REM RIGHT? INCREASE X
750 IF JOY=13 THEN P0Y=P0Y+2:REM UP? INCREASE Y
760 IF JOY=14 THEN P0Y=P0Y-2:REM DOWN? DECREASE Y
770 IF P0X>190 THEN P0X=50:REM SCREEN WRAP RIGHT
780 IF P0X<50 THEN P0X=190:REM SCREEN WRAP LEFT
790 IF P0Y>205 THEN P0Y=45:REM SCREEN WRAP DOWN
800 IF P0Y<45 THEN P0Y=205:REM SCREEN WRAP UP
810 RETURN 

1000 REM * VBLANK INTERRUPT ROUTINE *
1010 DATA 162,3,189,244,6,240,89,56,221,240,6,240,83,141,254,6,106,141
1020 DATA 255,6,142,253,6,24,169,0,109,253,6,24,109,252,6,133,204,133
1030 DATA 206,189,240,6,133,203,173,254,6,133,205,189,248,6,170,232,46,255
1040 DATA 6,144,16,168,177,203,145,205,169,0,145,203,136,202,208,244,76,87
1050 DATA 6,160,0,177,203,145,205,169,0,145,203,200,202,208,244,174,253,6
1060 DATA 173,254,6,157,240,6,189,236,6,240,48,133,203,24,138,141,253,6
1070 DATA 109,235,6,133,204,24,173,253,6,109,252,6,133,206,189,240,6,133
1080 DATA 205,189,248,6,170,160,0,177,203,145,205,200,202,208,248,174,253,6
1090 DATA 169,0,157,236,6,202,48,3,76,2,6,76,98,228,0,0,104,169
1100 DATA 7,162,6,160,0,32,92,228,96

2000 REM * PLAYER SHAPE DATA *
2010 DATA 66,129,129,153,153,255,255,255,255,153,153,129,129,66