>does anybody have an idea how this was programmed?
Probably much the same way as Big Dig. Big Dig uses Playfield graphics to do 7 different colours horizontally, the Rubik's Cube is also doing 7 colours per scanline.
Big Dig's display kernal (for the blocks) basically consists of:
lda $c0
STA COLUPF
lda $c1
STA COLUPF
lda $c2
STA COLUPF
lda $c3
STA COLUPF
lda $c4
STA COLUPF
lda $c5
STA COLUPF
lda $c6
STA COLUPF
lda $80
STA COLUPF
However the Rubik's blocks look a little smaller so they may be putting the routine into RAM and presetting the Immediate Mode address:
lda #$10
STA COLUPF
lda #$20
STA COLUPF
lda #$30
STA COLUPF
lda #$40
STA COLUPF
lda #$50
STA COLUPF
lda #$60
STA COLUPF
lda #$70
STA COLUPF
lda #$00
STA COLUPF
RTS
Since there's nothing else going on, there may be enough time between the end of drawing the right edge of the cube and the end of the horizontal blank to prime the RAM routine for the next scanline - LDA $ZeroPage/STA $ZeroPage x 7 = 42 + JSR/RTS = 54 cycles.
Yeh, should be possible....
Chris...
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