This is a good game. Not sure how to describe it - it's sort of skateboarding in a tunnel with obstacles. It's also pretty damn hard to do very well (at least, it is for me ;-).
On the subject of games - I watched the 25 minute trailer of Half Life 2 - wow. The game engine alone could very well be used to make just about any game you could think of. The detail of the images is awesome (although probably won't be on my crusty PC ;-). That's the sort of game to get a decent PC for - bring it on!