It's P.O.N.G. (Platforms of Null Gravity)

Duel to the death in a hollow spheroid, while the gods amuse themselves by watching you through their TV screen.

This 2-player HL2DM map is similar in premise to the arcade game, but not really, because you are actually standing on the paddles yourself, just waiting to be vaporized by a speeding orb of energy. -Unless you can vaporize your opponent first.