10 REM Example playfield using a redefined character set
20 REM By Jason H. Moore, Ph.D.
30 REM September 23, 2018
40 REM Thanks to character set code example from The Creative Atari
50 REM Thanks to machine language example from Atari Graphics & Arcade Design
60 REM Goal is to approximate playfield from Gene Medic for Atari 2600
100 MEMTOP=PEEK(106)
110 GRTOP=MEMTOP-4
120 POKE 106,GRTOP
130 GRAPHICS 0:POKE 752,1
140 SETCOLOR 1,9,9
150 SETCOLOR 2,9,2
160 CHRAM=GRTOP*256
170 POKE 756,GRTOP
200 REM READ IN MACHINE LANGUAGE ROUTINE FOR MOVING CHAR SET
210 FOR I=0 TO 49
220 READ DAT:POKE 1664+I,DAT
230 NEXT I
240 M=USR(1664,GRTOP,1,4)
280 REM REDEFINE CHARS A TO J
290 CHRAM=CHRAM+264
300 FOR I=1 to 10
310 FOR ADDR=CHRAM TO CHRAM+7
320 READ DAT:POKE ADDR,DAT
330 NEXT ADDR
340 CHRAM=CHRAM+8
350 NEXT I
400 REM MACHINE LANGUAGE DATA FOR MOVING CHAR SET
410 DATA 104,169,224,133,206,104,104,133,204,104,104,201,1,240,4,230
420 DATA 206,230,204,104,104,141,176,6,169,0,133,205
430 DATA 133,203,168,177,205,145,203,200,208,249,230
440 DATA 206,230,204,206,176,6,208,240,96,0,0
500 REM DATA FOR REDEFINED CHARACTERS
510 DATA 0,0,0,0,0,0,0,0
520 DATA 255,0,0,0,0,0,0,0
530 DATA 0,255,0,0,0,0,0,0
540 DATA 0,0,255,0,0,0,0,0
550 DATA 0,0,0,255,0,0,0,0
560 DATA 0,0,0,0,255,0,0,0
570 DATA 0,0,0,0,0,255,0,0
580 DATA 0,0,0,0,0,0,255,0
590 DATA 0,0,0,0,0,0,0,255
595 DATA 255,255,255,255,255,255,255,255
600 REM DRAW CHARS ON SCREEN
610 POSITION 0,7
620 PRINT "JJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJ"
630 POSITION 0,14
640 PRINT "DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD"
650 POSITION 0,21
660 PRINT "IHGFFFGHIHGFFFGHIHGFFFGHIHGFFFGHIHGFFFGH"
670 POSITION 0,22
680 PRINT "ABCDDDCBABCDDDCBABCDDDCBABCDDDCBABCDDDCB"
1000 GOTO 1000