Red Eclipse is a cross-platform, open source first-person shooter game that supports both single (against bots) and multi-player modes. The game runs on the Cube Engine 2 and it's very flexible, allowing players to extend the existing game modes (Deathmatch, Capture the Flag, etc.) with "mutators", changing how the game is played.

The game is based on the Cube 2 Sauerbraten engine and takes advantage of the features like a 6-direction height field world model, real-time map editing, light-maps, shader-based lighting effects, integrated physics support, and a particle engine.