After buying the orange box over a year and a half ago, one of the included games that I never got around to completing was Portal (as I primarily bought it for Half-Life 2: Episode 2 and Team Fortress 2 like everyone else). What a mistake that was!
Portal is a first person action/puzzle game that puts you in the shoes of Chell; the seemingly silent protagonist.
It’s set almost entirely inside the “Enrichment Centre” for “Aperture Science”, a research corporation responsible for creating the “Aperture Science Hand Held Portal Device” (portal gun).
The game takes place through a series of test chambers that pit the player against increasingly difficult challenges. All of these challenges revolve around using the portal gun to overcome some particular obstacle and are all excellent fun.

Portal Momentum Puzzle
The plot has a few amusing twists in it and is told through the narrative of GLaDOS, an artificial intelligence that directs the player through the test chambers whilst providing some amusing dark humour. All the while promising the reward of cake upon the completion of all test chambers.
Portal really is a game that needs to be experienced as my description of it really doesn’t do justice. The combination of unique game play, challenging puzzles and a humorous but simple plot line make for several hours of excellent fun!
Mate, it’s all about Portal: Prelude. What a mindfuck!
I’ve not got that pack yet. Still stuck on the advanced chambres!