703 The bit use of the PCOLR and COLOR registers is as follows: Bit 7 6 5 4 3 2 1 0 --color-- luminance unused Grey 0 0 0 0 0 0 0 Darkest Rust 0 0 0 1 0 0 1 etc. to: etc. to: Orange 1 1 1 1 1 1 1 Lightest When you enable the color overlap at location 623 ($26F), ANTIC performs a logical OR on the overlap areas. For example: 01000010 Red, luminance two OR 10011010 Darkblue,luminance ten -------- Result = 10011010 Dark green, luminance ten Here's a short machine language routine which will rotate the colors in registers 705 to 712: 10 DIM ROT$(30) 20 FOR LOOP = 1 TO 27: READ BYTE: R OT$(LOOP,LOOP) = CHR$(BYTE): NEXT LOOP . . PUT YOUR GRAPHICS ROUTINE HERE . 100 CHANGE = USR(ADR(ROT$)) 105 FOR LOOP = 1 TO 200: NEXT LOOP: GOTO 100 110 DATA 104,162,0,172,193,2,189,194 ,2,157 120 DATA 193,2,232,224,8,144,245,140 ,200,2 130 DATA 96,65,65,65,65,65,65 If you wish to rotate the colors in registers 704 to 711 instead, change lines 110 and 120 to read as follows: 110 DATA 104,162,0,172,192,2,189,193 ,2,157 120 DATA 192,2,232,224,8,144,245,140 ,199,2 If you wish to include all of the registers 704 to 712 in the routine, make the changes as above and change the eight in line 120 to nine and restore the 199 to 200 in line 120. This routine works well with the GTIA demos at location 623 ($26F). For further detail, refer to your Atari BASIC Reference Manual, pp. 45