> 1. Q*bert (red)
> 2. Q*bert's enemy (purple or green, flickering if there are multiple
> ones on one level)
> 3. Cube body color
> 4. Flying discs (white)
> 5. Background (black)
Q*bert and the enemy are obviously the two players. Cube body is
playfield. The flying discs are the unknowns. If I remember correctly,
they flicker (only one disc on each row is displayed per frame), so I
guess we'd have to assume the discs are either missile or ball, and the
color is changed immediately before or after display. (Notice the discs
don't move vertically - they disappear and Q*Bert just floats up to the
top by himself.)
> On scanlines with the cubetops:
>
> 1. Legs of Q*bert (red)
> 2.-4. the three possible colors for the cubetops
> 5. Background (black)
>
> All this without flicker!
>
> I don't know if this is comparable with your efforts, but it's surely
> remarkable. Wonder how they did that...?
Elementary, my dear Watson. By rewriting COLUPF between cubetops. There
is no other precisely timed effect on the scanline. All the kernel does
is rewrite the player's graphics for Q*Bert's legs, then rewrites COLUPF
every cube.
> And, in fact, Amidar uses three-color playfield, but it alternates
> colors by scanline, not by frame.
Well, if you're gonna think *that* way, then there's games like Chopper
Command that have a thirty-colored playfield in the mountains :)
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