My A*teroids clone "Comet Busters!" did this way back when, although you were limited to two sides (each of which could have 1-3 players) and the only inputs we

My A*teroids clone "Comet Busters!" did this way back when, although you were limited to two sides (each of which could have 1-3 players) and the only inputs were thrust, fire, left, right, "special ability". This was around the time DOOM had come out or was about to come out. Everyone had to exchange their inputs in one frame and then evaluate them in the next, so you were always a frame behind (1/24 of a second or so, or maybe 1/12). All math was fixed point which made it a bit easier. There was no resync; the game would just end if the checksums didn't line up, so lots of bugs were discovered this way :) Lots of time was spent figuring out how to handle start-of-game, since either player could initiate and we had to agree on a common screen size since it affected game play.