Get this game.

I know its a free game on the PC, but the Xbox Arcade released it with full multiplayer support for Xbox Live.

The gameplay is just awesome. You basically run, jump, etc around a self-contained screen like a maniac trying to get to the goal and pick up more time capsules. It plays like a mixture of Jumpman and NSMB on acid.

I believe it is also coming to the DS soon as well.