First multiplayer first-person shooter

Midi Maze (Xanth Software F/X, 1987) for the Atari ST exploited the system's relatively sophisticated MIDI ports to enable multiplayer action. It was the first example of a networked multiplayer first-person shooter. By connecting one of the computer's MIDI out to the next's MIDI in, it was possible to create a 16-player machine-to-machine network, which was an effective if rudimentary basis for multiplayer gameplay. Players in the game were represented as smiley faces and could fire bullet-like dots to take down their fellow gamers.