I did some fun work on MAME back in the day. I managed to get a hold of a PAL fusemap that was used in the Jr. Pac-man ROM encryption hardware. From there I cre

I did some fun work on MAME back in the day. I managed to get a hold of a PAL fusemap that was used in the Jr. Pac-man ROM encryption hardware. From there I created a little schematic and then implemented it in software inside MAME. The logic was stateful (it had registers) and so it wasn't something I could just run the ROM image through, so I ran the game with the encryption emulation running for each ROM fetch and built an unencrypted ROM image for the game while playing. After that I just released the unencrypted ROM image, but the decryption stuff was still sitting around in the MAME source last time I checked. I think I may have done the actual game emulation stuff for Jr. Pac, too—it was basically the same as Pac-Mac/Ms. Pac-Man with the addition of scrolling hardware and a bit that controlled whether the sprites showed up on top of or underneath the character/text graphics. That bit is so that during the cutscenes the sprites could be on one side of a fence or the other, or go inside a house. It's a single bit for all the sprites though, so if you pay attention to the cut scenes, when a character sprite goes behind something, all the other character sprites are away from the text graphics so that they don't go behind things as well.