How indoor
soccer works.

A professional match runs 60 minutes, split into four 15-minute quarters. A 15-minute interval follows the second quarter; three minutes separate the others.

Teams field five or six players and substitutions are unlimited. Some leagues allow a change while play continues, provided both players are never on the turf at once. The surface is artificial and the field far shorter than an outdoor pitch, which is what makes the game fast.

There is no offside. A few leagues operate a three-line violation instead: the field is divided by three lines into four sections, and a player who throws or kicks the ball over all three concedes a free kick to the opposition, taken from the middle of the first line.

The walls are part of the field. Playing the ball off one — or several — is not an offence. Only a ball that leaves the arena over the boards, or strikes the ceiling, gives the opposition a free kick. This is the mechanic the whole game is built around; it is set out in more detail on the game.

Three colours, not two. A blue card covers mild offences and removes the player for two minutes. A yellow costs five, and the side plays a man short for that time. A red leaves the team a player down for the remainder — though a red is much harder to earn indoors than in the outdoor game.