Is it possible to make the static BG(if I'm using the right terminology) completely static instead of jerky? Or would that be a matter of rewriting the game from scratch or having the source code?
Yes, that's completely possible. That's the first step, actually. I was able to disable the faux scrolling, but the BG maps need to be altered because all the faux scrolling parts are just black tiles (16x16 areas) - the game overwrites these blank tiles every so many scrolling periods. So no code, but it does mean sorting out the map data and altering it. The map data is not compressed, which is great, but I do need to figure out where the pointer table is (assuming there is one).
Another interesting note: The back ground is updated in three screen refreshes (if there's a lot), because the update routine they use is pretty slow.
The game also loads the entire game sprites into vram. Even the ones that don't get used for that level. It's sort of emulating NES sprite banks. It's a bit of a waste, and they could have used that extra space in vram for a smoother dynamic tile scrolling of the fake BG layer.
One other interesting thing is the sprite animation. They created one more frame of animation for most enemies. Not sure about the bosses.
