Rocketball (2001)

Rocketball is a futuristic strategic sports game for two players. Rocketball is avalable for free at:
http://www.invisible-city.com/play/62/rocketball

The object of the game is to guide the rocketball into your opponent's goal, but you can't touch the rocketball directly. Instead, you must place vortices and other obstacles in front of the rocketball to alter its course, guiding it to your objective.

Gameplay has a strong emphasis on tile placement and modification. The game comes with many variants and alternate game versions as well.