Metro is a 2D Gaming framework built around gosu (game development library). Metro makes it easy to create games by enforcing common conceptual structures and conventions.

A creator and manager for game rules and state, separate from displaying and controlling the game. The idea is that a primarily-simulation game may be written using Ruby rules and a connection to the Demiurge process, while control and display are handled separately. This approach is primarily useful for 'simulation' games rather than fast-reflex 'twitch' games.