Mugen is a 2D fighting machine where you download characters from other sites that people have made and play. You can also download addons for mugen that enhace gameplay. You can use cross-over teams that have never been thought of before like Shao Kahn vs. Chun-Li You can get mugen at ElecByte the website of the creators of mugen. There is only a DOS version and a Linux verion but soon Windows version will come out.