Cube 2: Sauerbraten (German for "sour roast", also known as Sauer) is a cross-platform, Quake-like first-person shooter that runs on Microsoft Windows, Linux, FreeBSD and Mac OS X using OpenGL and SDL. The game features single-player and multiplayer gameplay and contains an in-game level editor, its main feature. The game engine is free and open source software, under the zlib License, with commercial support available from the developer's own business counterpart, Dot3 Labs.
The aim of the project is not to produce the most features and highest-quality graphics possible, but rather to allow map-editing to be done in real-time within the game, while keeping the engine source code small and elegant.
The game started as a redesign to the original Cube game engine, and its first, developer-only, release was made on February 27, 2004. The latest release, dubbed the "Justice Edition", debuted on July 19, 2010, adding two new player models, thirty new user-created maps, several new game modes—including Efficiency CTF, Efficiency Hold, Efficiency Protect, Hold, and InstaHold—a mini-map, clock and crosshairs, among numerous other things.