There has been created a historical free game for Linux named 0 A.D and it is currently in the advanced stages of development and it needs your help! Take a look at the progress of this game and judge for yourselves: http://www.wildfiregames.com/0ad/ They currently are needing: artists programmers musicians And i thought there might be quite a few of those on this list! If you won't help this game will be released much later then hoped, so please help if you can.
