The sport of roundnet, aka "that yellow trampoline game" aka "if volleyball and foursquare had a baby" aka "enough with the wit I'd like to read the rules," is played 2 vs 2.
A player starts a point by serving the ball down onto the Spikeball net so it ricochets up at his opponents. The returning team has up to 3 hits between them (think bump, set, spike) to return the ball back onto the net. The rally continues until a team can't return the ball onto the net within their three touches.