Out of the 2007 "Orange Box" package the most impressive part was portal. A first person shooter with a twist. Your character instead of being equipped with some generic machine gun is in fact equipped with "The portal gun" an innovative weapon that allows the player to fire two portals, one orange, one blue. You walk in the blue one you come out the orange one and vice versa, it's a very simple concept.
However, thanks to some very ingenious level design this simple concept quickly becomes a puzzle tour de force. Throughout the game you will learn to utilize more complicated techniques that brings a real depth to the puzzles rarely ever seen. Its even possible to complete the most complicated levels in seconds when the gun is in the hands of the more advanced player.
However the thing that impressed me the most about Portal was the atmosphere created by a combination of an isolated feel, a sinister narrator in GLADos and an contrast in design between the earlier and the later levels, the sudden change between blank and bright, white levels and later on, dark grimy industrial style design. The aformentioned GLADos brings an evil feel to this isolation, you get the feeling that she's helping towards the end but that she hasn't prepared a very nice end for you.
Portal is a game for someone who is looking for something new done on the groundwork of a well worn genre. It truly is revelutionary and will hopefully inspire other develepors to pursue an innovative use of the FPS genre. Fuck it 5 stars all the way.