A new standalone version 4.0 of Prometheus is now available, built using the just-released Unreal Development Kit which allows the game to be played without owning any other Unreal-engine games. Prometheus can be downloaded from BeyondUnreal, FilePlanet (registration required), and Mod DB. Here's a bit on the game: "You're never alone when you have a clone. With the Prometheus Device, you control Einsteinian Physics laws of time and space. Create distinct past, present, and future Quantum States of yourself to solve puzzles and accomplish mission goals in this single player co-op game. You’ll need to keep your wits and memory sharp using an original game play mechanic presented in multi-dimensional format inspired by Portal and Mirror's Edge."