Street Fighter II is the game that created the modern fighting genre. Capcom released it in 1991, and its cast — Ryu, Ken, Chun-Li, Guile, Blanka, Dhalsim, Zangief, E. Honda — plus its six-button layout and quarter-circle special moves became the template every fighting game since has either followed or deliberately broken.
It's also where competitive fighting-game culture started: combos were originally a bug, discovered by players and kept in because they were fun. This browser version brings the arcade original to a tab, with keyboard controls mapped to the six buttons.
Quarter-circle forward — down, down-forward, forward — then a punch button. The dragon punch is forward, down, down-forward plus punch. These inputs have barely changed in thirty years of the series.
Yes, on one keyboard with a second set of keys, as it was in the arcade.
It established the modern fighting game: a diverse roster, six-button controls, motion-input specials and competitive one-on-one play. Combos, which became the genre's centrepiece, were originally an unintended bug that Capcom decided to keep.