Vault Lock

You're locked in a room. 

The only way out is the door, and the only way through the door is the circle scribed on its face. And the only place you'll get is the next room!

You escape using math. And if that doesn't work, try maths. Chain enough honest statements together and the bolt turns, the door opens, and you'll step into the room before the one after next.

Five circle-theorem keys, earned one at a time. Fourty (sp?) rooms deep, each starting as a single clean deduction and growing into long, quiet chains of reasoning. No arithmetic, nothing to type — just the shape of the proof and the slow turn of a lock. One room at a time, find your way out.

Donations are off here. If you have fun working your way through these rooms, go visit SomaFM instead — they're the station playing on the in-game radio, and they run on listener support.