Valve wants to break your head

Buried in the Team Fortress 2 hype, Valve has announced that an experimental puzzle FPS game called "Portal" will be bundled with Half-Life 2: Episode 2, anticipated for release on Steam in Q4 2006. It appears the "experiment" that Valve is performing here is one explictly designed to bend your noggin as much as possible. I don't think I've seen a more vertigo-inducing videogame clip since Descent.

Edit: Here's a link to the 720p HD version of the trailer.