Sylveondev/derpybasics3 ? reverse-engineered prompt

Build me a playable version of Derpy’s Basics, based on the decompiled Baldi’s Basics project, with the custom characters, challenge maps, and the two principals already mentioned in the README.

I want it to feel like a finished fan game, with a working main menu, a cleaner new GUI, and the core gameplay loop where you explore, collect items, and try to survive the characters chasing you around the school. Please make sure the challenge mode is actually selectable and works in game, and that the extra characters fit naturally into the experience instead of feeling tacked on.

If anything is unclear from the existing code, use the current project files as the source of truth and look up current docs online if you need to. Focus on getting the game running smoothly, making the new content accessible from the menus, and cleaning up anything broken enough to stop it from being fun to play.