Portal 2

Valve's gravity-bending puzzler caused quite a stir back in 2007 when it introduced perfectly executed bite-sized spatial conundrums to the world.

The sequel expands on what has gone before, mixing brain-bending puzzles with solid gameplay and plenty of laugh out loud incidental humour to create a fresh and quite brilliant experience.

Once again you take on the role of Chell, the sprightly test subject from the original game. She is still rattling around inside the confines of the Aperture Science lab, but the pristine clinical interiors of the first game are now debris-strewn and cracked after the fall of GLaDOS, the deranged and unstable lab keeper from the first game.

While the player is soon reintroduced to the monotone ramblings of GLaDOS, it is the arrival of spherical, one-eyed robot Wheatley which sparks the game to life. Voiced by the always excellent Stephen Merchant, Wheatley's West Country bletherings are the perfect counterpoint to GLaDOS's sardonic jibes.

Gameplay kicks-off in a similar style to the original, with Chell getting her hands on the portal gun. With this, the laws of physics are turned on their head, with Chell able to create entry and exit portals on walls, ceilings and angled surfaces.

The challenges Chell faces are devilish in their design and while the first part of the game is fairly straightforward - with most tasks using simple block and switch combinations - the player is gradually introduced to a variety of new devices which drastically alters the core gameplay mechanics.

Lasers have to be manipulated to trigger wall switches, fizzing neon Hard Light Bridges create platforms to out of reach places, Aerial Faith Plates send objects flying through the air, Propulsion Gel creates slippery slides, gloopy splatters of Repulsion Gel make trampoline-like surfaces and Conversion Gel allows Chell to add portals to inert materials.

But even though these new gameplay twists come thick and fast, it is to Valve's credit that utilising these devices to solve tasks never becomes frustrating or a chore.

There are no time limits involved, which lets the player take each challenge at their own pace, experiment with new ideas and futz about to their heart's content.

Gradually, everything snaps into place and Chell is free to scamper to the exit to face the next series of challenges. It's incredibly rewarding, too and there's an uplifting sense of accomplishment when completing what initially seemed an impossible task.

It's not a long drawn-out series of test chambers, either, with huge rusting environments replacing the confines of squared-off rooms in the second half of the game.

While the constant puzzle solving could have turned into a sombre slog, the witty dialogue elevates the experience and it's a genuine treat listening to pre-recorded messages and the hilarious musings of GLaDOS and Wheatley.

Valve have also given the player room to breathe between some levels, letting them have a nose around the vast facility, while Wheatley chatters away in the background.

Portal 2 is a fairly long game, clocking in at around the 10 hour mark, but even once the credits roll, the fun isn't over. Co-op multiplayer lets two friends combine their efforts to solve puzzles and in a brain-melting game such a this, I'll take all the help I can get.

With its slick production values, carefully crafted challenges, mentally stimulating gameplay and delicious sense of humour, Valve have created something truly special.

Portal 2 is quite simply a masterpiece and one of the most enjoyable video game experiences you'll have all year.