sentences:  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 "".Some games have even been ported entirely or partially by reverse engineering and game engine recreation such as "WarCraft II" through "Wargus" or "Commander Keen".