sentences:  Several game titles that were previously released for Linux were also able to be expanded or updated because of the availability of game code, including "Doom", "Abuse", "Quake", "Quake II", "Quake III Arena" and "Jagged Alliance 2".Some derivatives based on released source code have also been released for Linux, such as "Aleph One" and "Micropolis" for "" and "SimCity" respectively.Certain game titles were even able to be ported due to availability of shared engine code even though the game's code itself remains proprietary or otherwise unavailable, such as the video game "" or the multiplayer component of "".