Today I was doing some Bad End runs when I found a weird bug. It turns out the game must not be properly resetting in-game values after an ending is obtained (or at least Bad Ending, which is the only one I tested), because starting a new file after the credits has finished playing starts you at the 10th floor in the elevator and lets you get the Bad Ending in less than 30 seconds after starting a new file (it doesn't matter which file you start the new game on after the game enters this bugged state).

A few other things I found out:

-If you had the 11th floor unlocked (i.e. Stage 10 beat) before triggering the credits, it will also be unlocked in the elevator and you can get the Confused Ending immediately.

-If you had the screwdriver before triggering the credits, it too gets preserved to the new save file, allowing you to skip all of Stages 1 to 10 and start right from Stage 1 Hard in a True End run.

-Any and all secrets obtained and P-Switches triggered are also preserved.

-You still start the game with 2 TNT; floors bombed are not preserved, as far as I know. (Have not tested this thoroughly)

All in all, I obviously don't think this should be allowed on the leaderboards; it goes completely against the spirit of the Bad End and Confused End speedruns, and while it could be a bit interesting for True End, it would make no sense to selectively allow this glitch on some categories and not on others in this case. I do think it might make for a few funny misc. categories but it's probably not worth it. Still, though, I wanted to bring this to light, since despite all I just said, the currently ruleset doesn't technically ban this glitch.