M.U.G.E.N is a freeware 2D fighting game engine designed by Elecbyte.
The engine was originally released in July 17, 2001. Beta versions of it were made to work on DOS, Linux and Windows platforms, distributed through their website. The engine allows users to insert created characters, background stages, and other game objects through interpreted text files, graphics, and sound compilations to create a functioning fighting game similar to commercial games. While the engine is set up primarily for fighting game development, several other game types have been developed using it, including shooter and platform style games. Officially, Elecbyte claims to have forgotten what the acronym M.U.G.E.N stood for, but the readme documentation states that its meaning referred to the days when the engine was meant to emulate shooting games as opposed to fighting games.
The engine allows anyone to create characters, background stages and other game objects through interpreted text files, graphics, and sound compilations. It supports various types of audio formats such as MP3 and MIDI initially, although it can be configured to play various audio formats via Winamp plugins, such as ADX and OGG, as background music during gameplay or at other points such as an introduction or the select screen. The engine allows for most of the same type of functionality found in most any commercial 2D fighting games, up to and including close recreation of those games' characters and gameplay.
DOS and Linux versions
First released on July 17, 1999, M.U.G.E.N was initially created for MS-DOS. Development of the DOS version ceased when Elecbyte switched to the Linux platform in November 2001. M.U.G.E.N changes documentation</ref> For a time, Elecbyte had posted a request for donations on their site to legally obtain a Windows compiler to make a Windows version of M.U.G.E.N. However, the development group discontinued the project in 2003 and shut down their site. Later speculation pointed at leaks made public of a private Windows-based M.U.G.E.N beta that was provided to donators.
Win Mugen and subsiquent hacks
The private WinM.U.G.E.N beta contained a two-character roster limit, locked game modes, and nag screens. With the beta leaked and Elecbyte gone, a "no limit" hack that removed most of these limitations was made available in 2004, followed by subsequent updates to deal with bugs and other issues. This version of M.U.G.E.N. is functionally the same as the last Linux release, though with subtle differences and unique issues, mostly revolving around proper music and music plugin support. Because of the changes between the DOS and Linux versions of M.U.G.E.N however, many older characters required at least the SFF files to be modified to show palettes correctly (notably on portraits) as well as some changes in how certain CNS script controllers functioned, causing some minor upset and those that could still run the DOS version in some form sticking to that, as well as DOS patches to downgrade characters to be compatible with the older version of the engine.
Win Mugen Plus
In May 2007, a hacked version of WinM.U.G.E.N was released by a third party that added support for high resolution stages at the cost of losing support to standard resolution M.U.G.E.N stages. Later that month, another hack was done to add support for high-res select screens. In July 2007 another hack based on the last high-res hack allowed for only the select screen to be high-res and not the stages. In December 2007, a hack from an anonymous source allowed both low-res and hi-res stages to be functional in the same build, requiring only a single line of code to be added to hi-res stages.
Following the emersion of the new Elecbyte team in 2009, a new version of mugen has been put into development. Throughout 2009 and 2010 a series of release candidates were make public as the engine continued in development. In January 2011 the first official release of Mugen 1.0 was made available to the public.
Not all content developed for the mugen game engine is compatible across the various version of mugen, most notably are the screen packs which require heavy adjustments to be compatible from one version of mugen to the next, mostly due to issues with resolution. In general, most characters and stages are compatible across the three main windows versions of mugen all though the most recent version of mugen allows for a variety of updates that are not compatible with previous versions, most particularly the update to the graphics file.