Alien Arena is a fast paced multiplayer deathmatch game similar to Quake and Unreal Tournament, but with a deep sci-fi atmosphere, lot's of shiny and weird graphics and... aliens. The engine is based on the CXR game engine, but has been rewritten to allow a lot of new features and improvements such as 32bit high-resolution textures. The physics is based on the Quake II physics, but also allows dodging. It also features single-player matches against bots. View a YouTube demo here.
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Urban Terror is is an open-source multiplayer first person shooter based on the ioquake3 engine. It can be described as a hollywood tactical shooter; somewhat realism based, but the motto is "fun over realism". This results in a very unique, enjoyable and addictive game which reminds of Counter Strike, but is more action and speed oriented. View a YouTube demo here.
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Xonotic is a a free and fast-paced deathmatch FPS based on DarkPlaces, an advanced Quake 1 engine. It is a direct successor of the Nexuiz project and combines arena-style gameplay with rapid movement and a wide array of weapons. It could be considered most similar to Unreal Tournament and Quake at its heart, especially regarding teamplay and game mechanics. It features 18 official maps and many community contributions, has a lot of different game modes and claims to provide e-sports opportunities. It also provides an integrated statistics system called XonStat. View a YouTube demo here.
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