Argh, that's crazy :) This is very strange. I think that the updated version worked for some people, when it didn't work before.. and both worked for me on my hardware.
I will try to fix this, of course. I don't understand the mapper thing at all, there's nothing about it in the ROM headers, as far as I can see. Could you try the latest version of Gun Slugs and see if that works for you? https://spacepantsgames.itch.io/gun-slugs
Will do. I don't understand the "invalid header" error either. I messed with the rom with a couple of utilities but I'm not knowledgeable enough to understand the code. I can say that the MegaSD (with updated firmware) has a very good reputation for compatibility. I have about 465 games on there, not counting Sega CD and I rarely have an issue. Otherwise I wouldn't be bugging you. :) That said, I really appreciate you taking one more look at it. And congratulation on winning first place in the jam.
Oh you don't need to buy it! Your help has paid for it many times over.
Firstly, for the other ones, i wasn't setting up he SRAM info correctly in the header. Which is odd, cos I had it working fine in a previous game, so I assumed I hadn't changed anything.. but somewhere along the line I'd deleted it!
But for all the others, I remembered vaguely that you have to pad the game out to the cartridge size, so I wrote a little tool to do that and patch up the header. I also fix the checksum in there, but I don't think that's used by anything. At least Kega Fusion doesn't complain about an incorrect checksum now though! :)
