Cube 2: Sauerbraten is a free and open-source first-person shooter built around fast, old-school arena deathmatch — and around the idea that a map is never finished. Released in 2004 as the successor to the original Cube engine, it was developed by Wouter van Oortmerssen with Lee Salzman and Mike Dysart, and its defining feature is a full level editor that lives inside the game: switch to edit mode mid-match and you are dropping geometry, painting textures and relighting the arena while everyone else stays connected. The Cube 2 engine later spawned forks such as Red Eclipse and Tesseract, so this is where a whole family of free shooters began.

Key Features

• In-game cooperative map editing — enter edit mode without leaving the session, build and texture the level while other players stay connected, then jump straight back into play to test it.
• Octree / heightfield world model — the engine replaced Cube’s fixed cubic grid with a six-directional heightfield, so maps can have slopes, overhangs and stacked geometry rather than blocky rooms.
• Old-school arena combat — deathmatch and Capture the Flag plus mutations such as instagib, vampire and regeneration, on compact maps designed for constant movement and map control.
• Singleplayer with bots — an episodic single-player mode alongside bot matches on the standard multiplayer maps, so the game works offline.
• Lightmaps with dynamic shader lighting — efficient precomputed lightmaps with a stored directional component, enabling reflective water, underwater caustics and volumetric fog effects.
• Small, hackable engine — C++ with OpenGL and SDL in a deliberately compact, readable codebase; one of the easiest real shooters to read if you want to learn how an FPS engine works.
• Open source code, freeware game — the engine source is ZLIB-licensed and free to reuse; the bundled game media is not (see Licence below).
• Long-running mapping and modding scene — since 2004 the game has accumulated a large body of community-made maps, mods and scripts, and it still has an active community competitive scene.
• No accounts, no store, no ads — you download the game and play it; there is nothing to buy and no login.

Why Use Cube 2: Sauerbraten?

Most free shooters ask you to accept someone else’s maps. Sauerbraten hands you the editor instead: minutes after spawning you can reshape the arena you are standing in and have friends playtest the change immediately, which makes it as much a construction kit as a game to play. It is also the historically important link in free FPS development, since Red Eclipse, Tesseract and their descendants all began as Cube 2 forks, and its engine is small enough for one person to read end to end. A complete package is around a gigabyte, so it remains one of the lightest full 3D multiplayer shooters you can install on modest hardware.

Use Cases

• Casual LAN or online deathmatch sessions that run straight from a download, with no account or launcher.
• Designing and refining your own arena maps solo, or cooperatively with other players on the same server.
• Learning how a real 3D game engine is put together from a compact C++/OpenGL codebase.
• Keeping a low-spec, offline-friendly first-person shooter installed on older machines.
• Running a public or private edit-mode server with custom maps and scripts.

Platform

Windows · Linux · macOS — official standalone downloads (2020 Edition, 21 December 2020). The engine is portable and also runs on FreeBSD, OpenBSD and other Unix platforms from source.

Licence

Engine: open source (ZLIB). Game media: not libre. The engine source code is licensed under the ZLIB licence and is free to reuse in your own projects — the project’s README is explicit that only the source code is yours to use freely. The bundled game content (maps, textures, models and sounds) comes from many contributors under a variety of licences and copyright restrictions, so it cannot be redistributed as the basis of a standalone game. The game itself is freeware: the archive and installer may be redistributed unmodified, and it is free to download and play, with no advertising and no purchases.

Alternatives

• Red Eclipse — the most successful Cube 2 fork, with parkour movement, a modern Tesseract renderer and fully share-alike assets
• Xonotic — another movement-heavy free arena shooter, with a larger player base and a more contemporary engine
• OpenArena — Quake III Arena recreated with free assets, for the classic arena ruleset

Website

sauerbraten.org — source and downloads at SourceForge, documentation and wiki at cubeengine.com

Looking for more free games? Browse the Games directory.

Screenshot: Cube 2: Sauerbraten in-game water rendering — Johannes Schneider, CC BY-SA 3.0, via Wikimedia Commons.