Roofball

Roofball

"The best roofball ball is one of those cheap, light-weight jobs, about 10 inches in diameter, with all the swirly colors. You find them at the drugstore, dollar store, toy store, and even the supermarket when they're "in season". Of course, you may use any sort of ball that works for you...The basic game is played by 2 opposing players. They are both positioned on the same side of the building with the roof in question. Let me spell that out clearly in the negative mode: the players do NOT play on opposite sides of the roof. One player hits the ball up on the roof. Gravity (whatever that is) causes the ball to slow down, stop, change directions, and then start back down the roof, picking up speed as it does so. After it comes flying over the edge of the roof, the other player is obliged to smack it back up on the roof. As in tennis, a player has the option of hitting the ball "on the fly" - that is, before it hits the ground - or else letting it bounce once on the ground before hitting it back to the roof."

There's more. There's lot's more. There's also this.