When Valve announced after Half-Life 2 that they were going to do some episodic adventures in the series, we were excited as it meant more Half-Life quicker. It turns out that wasn’t the case though with Valve recently saying they are pretty much done with episodic and the pressure to get software out on time. However, rather than ship Episode 2 alone they added a few new funky features, and it seems the one with the least amount of hype has become the best. Portal is a triumph in PC gaming that in originality stakes could take a very long time to top. It's fun, quirky and above all part of one of the most value packed packages in ages.

Portal places you in the role of an unnamed test subject in the Apeture sciences laboratory. It begins when you wake from an induced slumber only to find yourself the plaything of an AI computer. From there it's 19 levels of puzzle solving with the portal gun until you eventually get some Cake, though there is a twist or two along the way. The storyline is not the strongpoint for Portal, that comes more from the gameplay.

On offer you have two types of weapon; a gun that can shoot one portal, and then later one that can shoot two. Basically you have a blue and a yellow portal. Walking into the blue will bring you out of the yellow. It is this basic mechanism that shows how ingenious Valve can be as developers and how original the game is. Portal is definitely a game where you need to think outside the box to solve the puzzles. The first half of the game is exceedingly easy but that is because Valve realised they have to slowly teach this new mechanism to you. By the end you will be tearing your hair out with some of the puzzles.

To give an example of how the Portal system works, imagine a room with a turret blocking your way. You have no weaponry other than the portal gun so you have to think with your brain and not with power. A simple way to solve this would be to place a blue portal near you, and a yellow behind the turret. Walk through the blue and out the yellow, then push the gun over from behind. Simple. It is this simple style that has Portal up there as a surprise contender for Game of the Year on PC and its not even meant to be a major part of The Orange Box.

For those who manage to complete the game (and it will only take about two or three hours), you can also try the advanced versions of the puzzles as well as take on the time challenge mode. There is already a crazy amount of videos of people completing the levels quickly and this is sure to grow as word of mouth spreads about this superb game.

One area which possibly disappoints is the visuals. Using the 2007 version of the Source engine, it still doesn't stand up to most of today’s big games, especially on the console side of things. However this is definitely gameplay over graphics and this is where it delivers in spades. The other enjoyable aspect of the game is the voice acting and how the protagonist plays with you and teases you. One level for instance the protagonist will continuously tell you that this level is impossible and you should not try to complete it, until of course you do.

Another excellent feature which Valve has included with all the Orange Box titles is developer commentary. When you complete a level you can then turn on the commentary nodes which gives you an insight into how Valve develops its games and the challenges this new style of game produced. It really shows just why it takes so long for Valve games to hit the market, due to the amount of refinements. At least this one didn't take ten years like Team Fortress 2. Using the HL2 engine will also allow those with the skills to make new Portal maps for download so it will be interesting to see what the community comes up with. However, even if that doesn't eventuate, you will find yourself wanting to play Portal over and over again, trying to get a quicker time, or just to waste away a few hours.

This little gem gives a whole new perspective to the Half-Life series. While Valve won't reveal just how Portal fits into the HL universe yet, there are many references to Portal during Episode 2 and considering what an ingenious concept it is, we expect to see much more Portal from Valve over the coming years. We continuously badger developers to give us originality, and for once a major developer has. Portal is simply a must play title, even for those who are not necessarily puzzle fans.