If you haven't heard of it then I'll enlighten you. The basic concept is that you have a 'portal gun' which, as the name implies, creates portals which you can instantly travel though. It also has the same functions as the gravity gun from Half-Life. This introduces heaps of new gameplay elements, such as opening a portal over something that is firing at you, and then creating another portal beneath a crate. The crate will then fall through the hole and hit the aggressor.

The game is set in the Half-Life universe, and will be shipped for free along with Half-Life 2: Episode Two.

Here are some videos showing the concept in motion (via YouTube):

Trailer: http://www.youtube.com/watch?v=if3Qv2tHyfA
Gameplay video: http://www.youtube.com/watch?v=nTzUdTIglTk

Personally I think the concept is absolutely amazing. Though it may appear to be ripping off Prey, in actuality Portal has been under construction for quite a long time. Besides, in Portal the game revolves around these holes, whereas in Prey it was more of an add-on. I can't wait to try it out.

That looks like possibly the most origional game concept I have ever seen inm my life, seriously.

This is a game that definitely deserves a place on my Christmas list I can tell you that now.

I have to agree it is original in concept, it like a mix of myst for it puzzle's and run of the mil fps game. do you have any idea what game magazines rated this game at all?

The game isn't actually out yet, so there are no ratings thus far.

Oh wow! VERY cool!!! Graphics are amazing, concept and idea are unbelievably original, looks like great fun! Kinda hard as well though. Hehe, any info on when this comes out?