bi-balling

When playing a mono-ball sport with two balls. Can also have tri-balling and quadruballing, etc.

The complexity of the game is 'n' times more than if there was only one ball where n=(number of balls in play) - 1

e.g. tri-ball soccer is twice as hard as mono-ball soccer (3 balls - 1=2)

Rubeus Hagrid: Gonna go play quidditch today Harry?

Harry Potter: No, but there's bi-balling tennis happening later!