From Halopedia, the Halo wiki
A variant of pool called Moons exists in the 2500s. Its revised rules include reversing the laws of movement. A ball, when struck hard, will move slowly, whereas if it is struck softly, it will move with greater speed.
Thin Kinkle is a fan of the game, and often hangs out with his gang at a moons parlor called Sharfie's. It is there that he first met Janissary James.