I don't know the exact answer to this, but the minus world is always the _same_ level data, even if that level data is invalid. The same was the case in my game

I don't know the exact answer to this, but the minus world is always the _same_ level data, even if that level data is invalid. The same was the case in my game, the "5th level" was weird garbage, but it was always the same weird garbage. I suspect because SMB was a better architected game than what I wrote, the unpacking of the level data is substantially more reliable. There's a very interesting video that shows what you get if you keep incrementing the current-level byte, though I doubt there's a way to do it in game like you can with world -1 https://www.youtube.com/watch?v=riaf2vwMzMo https://www.youtube.com/watch?v=riaf2vwMzMo