Still a bug, and circular wipe again

First task tonight was to try to understand why the Apple II Lode Runner attract screens were non-deterministic. I think I've found the answer, and it was even semi-documented in the 6809 source code. However there are still inconsistencies between the Apple and C versions I can't explain at this point so it would appear I still have a bug somewhere, perhaps not even in the AI as such. It needs further investigation.

Second task was to determine if the "circular wipe" that was part of the Apple II version (and very few other ports) is feasible on the Neo Geo. I had the idea to employ the sprite shrinking capabilities of the Neo Geo hardware in order to "get it for free".

However the "free" solution requires setting sprite positions outside the visible display, which is not possible unfortunately. So I set about trying to devise another, necessarily more complex, scheme that would be workable.

I think I have worked something out - on paper at least. It's not too complex and doesn't require much in the way of run-time calculations and does employ sprite shrinking. The only caveat is that I'm not sure how it's going to look when it's actually animated.

There are two ways forward from here. One is of course to simply implement what I have devised and run it. The down side is that I have to re-learn everything I have forgotten about sprite formats and sprite manipulation, and then write code to create the requisite sprite tiles and the code to assemble and control them properly. And if that looks naff, it's all a wasted effort.

The other is to simply "emulate" the Neo Geo's sprite shrinking in a suitable development environment (my go-to has always been Allegro on the PC) and code a pre-canned animation. There is I believe sufficient information on the NeoDev Wiki to do exactly this. It's probably less work, and requires less mental effort on my part, until it comes time to implement it on the Neo Geo itself. The only caveat is that it may look different on Neo Geo hardware if I get something wrong.

One other option of course is to give up on the circular wipe altogether. As I mentioned, not many of the other Lode Runner ports include it, though I'm not convinced that the reason isn't the rather annoying pause whilst it was rendered, rather than technical reasons (on the bit-mapped platforms at least). Some ports chose a different "wipe" animation whilst some didn't bother with anything at all.

But I would like to keep the port as close to the Apple II original as possible; it serves to reinforce the origin and the accuracy of the port. So I might give the "emulation" approach a go when I next get to work on it.