Cool project! I'm very interested in accurate preservation of the behavior of these old systems (chip decapping and scanning, FPGA reimplementation, accuracy-focused emulators) and using Ghidra to reverse engineer old games, especially on the 6502 and m68k architectures. Just an enthusiastic spectator at this point, but I hope to contribute something to the field eventually.
A sidenote: the action at 0:19 in the 50x-speed demo is intriguing. I've played many hours of Super Mario Brothers and watched various tool-assisted speedruns of it, but I don't recall seeing a Goomba reverse direction like that instead of just plowing into Mario. Is that a game glitch that you intended to show off with your recorded keyboard inputs? I haven't played in a long time, so I also wouldn't be surprised to hear that such behavior is common. I didn't find an obvious reference to it in the TAS info here [0].
Edit: there is precedent for that Goomba behavior [1].
I think that goomba bumped into the squished goomba Mario had just squished. Mario was just a bit to the left so the flat goombas hit box stuck out to the right a bit and the other goomba hit it.
A sidenote: the action at 0:19 in the 50x-speed demo is intriguing. I've played many hours of Super Mario Brothers and watched various tool-assisted speedruns of it, but I don't recall seeing a Goomba reverse direction like that instead of just plowing into Mario. Is that a game glitch that you intended to show off with your recorded keyboard inputs? I haven't played in a long time, so I also wouldn't be surprised to hear that such behavior is common. I didn't find an obvious reference to it in the TAS info here [0].
Edit: there is precedent for that Goomba behavior [1].
[0] https://tasvideos.org/GameResources/NES/SuperMarioBros
[1] https://www.reddit.com/r/Mario/comments/add1fx/changing_goom...