Legal return

After the ball is legally served, one of the players on the receiving side must strike the ball either on the fly or after the first bounce, and before the ball touches the floor the second time, to return the ball to the front wall either directly or after it has touched one or both side walls, the back wall, the ceiling, or any combination of those surfaces. A returned ball may not touch the floor before touching the front wall. A ball may be played off the back wall as well as the front wall, provided the ball does not touch the floor a second time. Failure to make a legal return results in a point for the server.