IGN has a preview up for Valve's new game, Portal which is basically a first person puzzle game running on the HL2 engine.

Portal, part of Valve's Orange and Black boxes to release this Fall, differentiates itself from the other games including its cousins Half-Life 2 and Team Fortress 2, in that it's not a first-person shooter. It takes place from a first-person perspective, but it's essentially a puzzle game. We got a chance to play through a few introductory stages at GDC in San Francisco, and though we didn't get to see very much, we saw enough to know we wanted more.