Chromium B.S.U. is a classic arcade raster graphics vertical scrolling shoot 'em up single player game. It was written with games like Raptor in mind and the idea to enhance them for modern graphics. As such it uses opengl via media-libs/freeglut or alternatively sdl, supports fullscreen and modern audio themes. View a YouTube demo here.
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OpenClonk is the Open source successor of the Clonk gaming series, being a multiplayer-action-tactic-skill game. You could say it's an interesting mix of The Settlers and Worms. In a simple 2D antfarm-style landscape, the player controls his crew of Clonks, small but robust humanoid beings. The game encourages free play but the normal goal is to build a mine and exploit the earth from valuable resources or fight each other on an arena-like map. Development is especially focused on Bustling mining, production lines and economy, fast and fiddly melees. Another focus lies on the further enhancement of the game engine and the extensibility/modability of the game content with C4Script. View a YouTube demo here.
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Minetest is an infinite-world block sandbox game and engine, heavily inspired by Minecraft and InfiniMiner. The majority of ingame content is provided by the community in the form of mods, as well as texture packs. Mods are installed on the server-side and there are already quite a few dedicated servers running you can join. The engine is written in C/C++ and is meant to be portable and lightweight and should run even on fairly old hardware. Supported platforms are Linux, OS X, FreeBSD and others. Features include building, crafting, multiplayer, lightning graphics and a map generator. View a YouTube demo here.
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Supertuxkart is a free kart racing game starring Tux. It's a fork of TuxKart and under active development. It features single-player, multi-player and a story mode. You can choose from a lot of funny characters including Tux, Mozilla, Pidgin, Puffy and of course the GNU. There is also an addon manager integrated, you can find some addons here. The gameplay combines regular kart racing with the possibility to collect items on the tracks with different properties (such as a cake bomb or a glue-like stuff to slow down opponents). You also have to look out for fuel items you can use to boost your speed for a short period of time. This makes the gameplay much more fun and reminds a bit of Super Mario Kart. View a Vimeo demo here.
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