Air-Sea Battle question...

glurk · April 7

So I had the idea to use @DEBRO's disassembly of this, and make a cleaner version. First I made it 4k ROM to have more room, and then I fixed the presumably unintentional mid-scanline color changes. I've attached that version below.

Next, I "wanted" to see if I could implement early HMOVE to get rid of the black bars. And I kind of did (not posting it), but the missiles went crazy. It appears they use HMM0 and HMM1 positive and negative values for their trajectories. And of course, early HMOVE values only pull LEFT.

So, I guess this is essentially impossible? Or it would require an early HMOVE for EVERY scanline (or every 2, I suppose...)

Anyone got any thoughts on this? It doesn't matter if it can't be done, I'm just trying to further my knowledge here.

EDIT: Upon a second look, even the version I posted here is not quite working... Sigh.

AirSea.bin

Edited April 7 by glurk

+Omegamatrix · April 8

It should be very possible. I haven't looked at the dissasembly at all, but essentially you have to adjust the positioning routine so that the "rough" positioning is never less than what the final positioning should be, and never greater than 16 pixels away. There might be an exception though when positioning to the extreme right of the screen... you might have to rough position on the far left side of the screen and then wrap around to the right with the fine adjust if you are using HMOVE on the same scanline at cycle 73 or 74. This might not matter for this game if the missiles never go to the far right edge.

glurk · April 8

Yup, I'm starting to see how to do it. But this game is coded so weirdly and eccentrically I think it would be more trouble than it's worth. I sort of thought it would be easy, but it's not. Here's a totally borked "demo" of sorts, which only partially works. And my added code is whacky, LOL. I don't think I will continue on this one...

AirSea.bin