Mortal Kombat

Midway filmed its fighters on video: actors in costumes were run through frame by frame, the frames were processed and put into the arcade machine as sprites. That is where both the look of the game and its limits come from. The set of moves equals what got filmed, so the characters share many animations and a common silhouette, and what sets them apart is above all their special moves. Block is put on a separate button, even though the genre convention was to pull the stick back. This changes the geometry of a fight: you can defend without retreating, and distance is kept differently than in Capcom's machines.

The finishing move works as a separate layer of input. After the winning round the loser stands stunned, and in that window you enter a sequence that only works here and has no effect on the outcome. The move isn't needed to win; it's there to be known and shown off, and swapping such sequences made up a noticeable part of the talk around the machine. The violence shown on screen took the matter beyond the arcades: in 1993 games were examined at hearings in the US Senate, and in response the industry set up its own system of age ratings, which had not existed before.