Portal is a game created using the Half Life 2 Game Engine and is part of the Orange Box from Valve.
The basic premise of the game is that you have a gun that opens a Portal Entrance and a Portal Exit. You have to position these portals in such a way that enables you to move throughout the game, usually bypassing obstacles and what not. One example is the player is pinned down by an automated gun. He opens an exit portal directly above the gun and an entrance portal next to himself. He then pushes a crate through the entrance portal that drops directly on the gun thus destroying it and clearing the way for the player to proceed. Nifty, huh!
The game is apparently a lot of fun and a very unique take on the First Person Shooter. The PA guys gave it the good word and they have yet to steer me wrong. Here is the comic they wrote for it as well.
Anyway, the video below is the song at the ending during the credits. Listen to the lyrics. It’s quite enjoyable.