The tennis court is overlaid with a hex grid, and players use a rubber-band mechanism to hit the ball. The Monkeys are used only to note the location of the player on the court -- they could have just been cubes, but look much better this way. Each player has a limited amount of movement when hitting or returning a shot, and then can "borrow" from their next move but this puts them under pressure and thus limits their ability to shoot most effectively.