Portal was first seen in The Orange Box, along with the classic Half-Life 2 and its expansions, as well as Team Fortress 2. Not too much was expected from Portal - after all, its developer Valve only made it for a kind of test. However, it turns out to be one of the best games they've made. You can't get much better; the story is gripping, the gameplay is unique and there is some terrific voice acting. Now, you can get The Orange Box for a tenner, so it's worth giving it a go.

Right, the story...really, there's not much I can tell you without giving away any spoilers. Basically, you are a test subject at Aperture Science labs. You must go through each test chamber, completing various puzzles. Through speakers, a voice of someone named GLaDOS will guide you. Right now, you may be thinking that the plot sounds a bit boring. Get it, though, and you will discover why Portal features one of the best storylines in any game.

Onto the gameplay, now. Portal is a first-person game, but far different to the typical Call of Duty-type gameplay. You hold a device called the ASHPD (Aperture Science Handheld Portal Device). Interestingly, these initials are a shortening of the name Adrian Shephard (the main character from Half-Life: Opposing Force). This device can fire two different Portals: blue and orange. If you fire both at a wall and step through the blue one, you will come through the orange and vice versa.

Does it sound a bit simple to you? If you are, you won't be thinking the same when you play. Some of the puzzles you come across in Portal are extremely challenging. At first, they are simple, but soon after they get a lot harder and involve angular velocity and momentum (I would go into depth with this, but its far too hard to describe!). Death will become a problem too - sometimes you have to figure out a way to get through rooms filled with a green, deadly liquid.

Just like in Half-Life 2, the graphics in Portal are superb. The environments are detailed and look realistic. Every now and then, you just look around the room you're in and appreciate how good the game looks. However, they aren't perfect - the walls, ceilings and floors are all white for most of the game, so Portal doesn't always show off the graphics to their full potential.

Sound-wise, Portal is flawless. Ellen McLain, who voices GLaDOS, shows expression in everything she says. When she makes a sarcastic comment, she says it in a sarcastic voice. When she's angered, she shows anger in her voice. That's the only voice work in the game, sadly, but its perfect. The game features music on several occasions and like the voice acting, the music is excellent. It suits the atmosphere of the game. Fast music plays when you are in a quick-paced section and slow, tense music plays when you are at the more dramatic parts of the game. The song at the credits, Still Alive, is the cherry on top. This features Ellen McLain's voice. Written by Jonathan Coulton, the lyrics are extremely funny, guaranteed to make you laugh out loud. It might even be worth getting the game just for that!

And finally, the system requirements.

PC Minimum Requirements:

1.7 GHz Processor
512MB RAM DirectX® 8.1 level Graphics Card (Requires support for SSE)
Windows® 7 (32/64-bit)/Vista/XP
Mouse
Keyboard
Internet Connection

PC Recommended Requirements:

Pentium 4 processor (3.0GHz, or better)
1GB RAM, DirectX® 9 level Graphics Card
Windows® 7 (32/64-bit)/Vista/XP
Mouse
Keyboard
Internet Connection

Mac Minimum Requirements:

OS X version Leopard 10.5.8
Snow Leopard 10.6.3, 1GB RAM, NVIDIA GeForce 8 or higher / ATI X1600 or higher
Mouse
Keyboard
Internet Connection

Overall, Portal is amazing. The story is seriously gripping and immersive, possibly even surreal. The gameplay, as I said, is unique and nothing else quite like it has been seen before. The graphics aren't flawless, but great looking all the same. The voice acting and music is excellent, and the credits song, 'Still Alive' is one of the most memorable and funny songs in gaming history. As an added bonus, you don't need a very powerful computer to play it. Sadly, it only lasts about five hours on your first playthrough. The value for money is still excellent, though!

Price: Portal £19.99 (Amazon.co.uk)
The Orange Box £10.36 (Amazon.co.uk)
Developer: Valve
Publisher: Valve