Coining up, but scrolling will need to be revisited.

Some good and some bad news.

First the good news; transcoding of the high level structure and attract mode screens has been fairly straightforward. It cycles through the 4 screens - sort of, no gameplay - and prints a handful of messages. I can also coin up for 1 or 2 players. They are by no means complete though.

Coined up on the Neo Geo

The bad news; I'm going to have to re-think the background scrolling. Not so much the mechanism on the Neo Geo, but rather how it keeps track of where it's reading the map and where in video RAM is currently visible.

Without checking properly, I assumed that the only place the background layer was being accessed (written) was the map. This (incorrect) assumption allowed me to all-but-ignore how Xevious was doing it and come up with something easier to code on the Neo Geo. Well, that all came crashing down when I (re)-discovered that portions of the Xevious logo are actually rendered on the background layer.

And in the process it needs to position the visible area at a fixed location, which is not a function that I currently support. But it's not a deal-breaker by any means; I just need to revisit it at some point and emulate the actual hardware more accurately. I will do so with a better understanding of the Neo Geo hardware in any case, after the recent experiments with scaled sprites.

For now I'll press on with the high level structure, and flesh it out so I can start a game. This will allow me to start adding (Xevious) sprite support, and then things will really get interesting!