Mortal Kombat Project is a M.U.G.E.N project which focuses on Mortal Kombat. The game has undergone several revisions, including a revision that made this game almost completely different from the original game. Since it's first release, the game has improved in many ways, such as improving the game engine and adding additional characters that either appeared in later Mortal Kombat games, or are based off already existing Mortal Kombat characters, such as Human Cyrax.
The game is currently at 4.1; version 5.1 was originally planned for a 2009 release, but the project has apparently been discontinued since then. In the absence of an official update, Mortal Kombat Project has since served as the basis for several other Mortal Kombat-inspired full-game projects, with most of them being direct modifications of the original game.