Mugen (stylized as M.U.G.E.N) is a freeware 2D fighting game engine designed by Elecbyte. Content is created by the community, and thousands of fighters, both original and from popular fiction, have been created. It is written in C and originally used the Allegro library. The latest versions of the engine use the SDL library. Gameplay The engine uses four directional keys along with seven buttons for gameplay (A, B, C, X, Y, Z and Start), in order to accommodate six-button fighters which use three punches, three kicks and a start button which is often a taunt. However, characters do not necessarily use all seven buttons, nor need to follow a traditional six- or four-button format. At most, two players can control characters, with others being controlled by the engine's AI (including Watch Mode, a demo mode where the computer controls all characters). AIs can be brutal, strong or even weak. The default AI for the engine however, can walk around, jump around, rarely attack and guard the player's attacks when the AI Level is set to Hard. In addition, several gameplay modes are available via the main menu. The first gameplay mode is the Arcade mode, where a player controlled character encounters CPU controlled characters in a random or set order which can be entirely customized. There are also three different kinds of Team modes: Single, Simul, and Turns. A fourth mode, Tag, is listed in the EXE along with two related script controllers, but was never used. In Team mode, either side can use any of the team modes. Single is identical to not having a team, Simul gives that side a computer-controlled partner who fights simultaneously, and Turns uses a different character for each round of play, varying through a set number (usually from 2 to 4) of different characters in a row. If set, the characters' starting life will be adjusted according to the number of players on each side. If one side has two characters and the other has only one in one of the Team modes, the two characters that are on the same side will each have half their respective normal maximum life values. Pre-Win M.U.G.E.N versions of the engine could have this feature adjusted or disabled via the options screen or the config file, but due to the nature of the hack, the option has not yet been reactivated. Team Co-op is similar