Looking good on the AES!

I've fixed the black line (missing tiles) issue on the background. Turns out you need a rather lengthy delay after setting the VRAM address register before you attempt to read from VRAM. Much better to avoid having to read altogether, so I re-wrote the background color/video RAM access routines from scratch. In a way it's turned out even simpler than before; there's effectively a single routine to do both now.

Running on my AES with only a few minor glitches now

Whilst play-testing on the AES, I found one or two new gameplay issues. One is interesting - at one stage a bunch of Jara appeared on the screen, and as they changed direction they morphed into Toroids! Quite apt because they both have very similar, if not identical, flight patterns.

Another I have seen before, I just haven't had time to chase it down. At a certain point, every hit earns you extra Solvalou, which is reportedly the same bug that occurs when you reach 9,999,990 points!?!

And another I've just noticed now after coming back from leaving the game running (with invincibility enabled) for an hour or so; looks like some bullets aren't being destroyed when they leave the screen.

UDATE: I've ust realised those bullets are OK; they're from the Zoshi circling the invincible Solvalou. However there are a couple of other bullets just hanging stationary in mid-air - I'm not sure where those came from...

I'll leave the gameplay bugs until last whilst I'm focused on getting the game running glitch-free on real hardware. Next I'll tackle either the scrolling or optimising the sprite usage/lifecycle. I had to back out one change that reduced the number of Neo Geo sprites per line by 4, so I also need to work out why that was causing the last line on the foreground tile layer to disappear.

But overall, there's no show-stoppers and I think I'll have it running quite nicely within a few weeks. I've even started thinking about sound...

UPDATE: I've deactivated the invisible 4 rows (sprites) on the foreground layer - properly this time!

UPDATE: Enabled invincibility and left the game running for about 10 hrs today - it was running just as well at the end as it was at the start, so no gradual degradation or glitches or memory leaks it seems.