Various methods such as joypad adapters and link systems are employed to allow multiple players to compete, up to a maximum of 8.
Ai is the only way to control your bot: there is no way to control it through the keyboard or joypad.
The game requires a six-button joypad for proper input, although, only the low punch is absent on the original three-button controller.
The game would have two extra joypad ports built into the cartridge itself, thus negating the need to buy extra hardware (beyond two more joypads) to play four-player games.
When using a rotary controller in one player modes the second controller port and a standard joypad are used for some bonus levels and entering the players initials.