Game Idea: Volume Infinity. The last book in a series, with the rules for generating them all.
Game idea: "The whole garden may be read as a book, or as a spell, which is, after all, the same thing. If you knew the words, you could speak what the garden says and you would then be able to control one of the countless forces that act in the sublunar world."
- Foucault's Pendulum
Game idea: Reordering a program that has had all tokens put in sorted order.
Could work on various levels, bits or bytes of machine code, assembly instructions, lines of a higher level language (probably indent or begin/end keyword based). Maybe some are unreachable garbage. See: Parsons Problems
Game idea: Machine Code Roguelike.
You can reprogram the world to do magic, but if you trip any security features you die, getting a new, randomly generated world, with new architecture and security rules. Maybe construct a higher level interpreter, port into each run as you discover its structure.
A lot easier, to implement and play, without the roguelike permadeath and procgen. Maybe a prebuilt set of worlds with very different underlying rules, retryable so you can learn from your own mistakes, instead of trying to find instructive craters. And more feasible to build the game code in each.
Game idea: Amanuensis. You copy out occult manuscripts. All nonsense, but you develop techniques of encoding and error correction that become useful elsewhere in the game world.
If you're lucky there might be some existing arcane scholarship, or easy access to inspect the world's code, or late security checks (in the spirit of Spectre but easier to exploit).
A big part would be finding evidence in each world from people who already failed.