Portal 2 action-puzzle game

Originally released in 2007 as part of the Orange Box bundle that included all the Half Life 2 titles, the first Portal game could have been easily dismissed as little more than an amusing nugget. But with its inspired quantum physics puzzles and quirky sense of humour, the short-but-sweet title was, for many, the star of the show.

Rightfully, Portal 2 gets its own release this time around. The single-player campaign is a little on the brief side but it's joined by a separate two-player co-op campaign as well as the promise of further free downloadable episodes and user-generated content, all of which easily justifies the entry fee.

Veterans of the first game will find that the Aperture Science underground test facility has fallen into a state of disrepair since their last visit but the premise essentially remains the same. Played from a first-person point of view, the game quickly gives you ownership of the Portal Gun. This allows you to shoot two portals onto specific types of surface; enter one and you will come out of the other. Your aim in each level is to reach the exit but it's rarely obvious as to how this can be achieved. Buttons, cubes, lasers and, later in the game, various gels with special properties all come into play and your task is to combine these with your portal-creating abilities in order to reach the end of the stage.

Along the way you will encounter some robotic characters and recorded voice messages. The same politely murderous artificial intelligence Glados makes a return and is as sadistic and sarcastic as ever ("The test results are in: You are a horrible person. That's what it says. You're a horrible person. We weren't even testing for that."). She is joined by a hilariously inept spherical droid voiced by Stephen Merchant. The genuinely witty dialogue brings an extra layer of amusement to proceedings.

Unusually for a recent release, Portal 2's relatively undemanding system requirements mean that it will work well on a range of different computers, including Apple Macs, laptops and some older models.

Ingenious, witty and challenging without ever being frustrating, Portal 2 is one of the most consistently enjoyable and entertaining games we have played for a long time.