Mugen is the 2d graphics engine that allows you to create fighting games in the style of Street Fighter, King of Fighter and others, created by the software house Elecbyte back in 1999, with the C programming language.Thanks to Mugen you can create your own fighting game style, customizing it 100%, inserting the characters you prefer, the stages related to each character, the entire graphic interface, in short, the entire game is totally customizable.You can read More on Wikipedia.