After a few hours of playing Mercury Meltdown, the sequel to last year's roly-polly action puzzler Archer Maclean's Mercury, we had to continually remind ourselves that PSPs cost $250, and it is therefore unwise to shatter them into tiny pieces with hammers. Not because the game is bad; far from it, as tilting precarious aerial platforms to guide a blob of liquid metal around is surprisingly addictive.

No, it's because every time that blob drifts slightly over an edge, a chunk of it falls off, reducing our score. And if we're really unlucky, the rest of it follows, forcing us to start the level over. And that doesn't get any easier when we try to navigate it over slick surfaces or through winding mazes. But as frustrated as we are, we still want more. The mercury, she is a harsh mistress.

At its core, Mercury Meltdown is about little more than getting a silver blob of goop from point A to point B before the timer runs out. Like in fellow puzzle games Super Monkey Ball or LocoRoco, you tilt the blob's environment rather than controlling it directly, and attempt to roll it - or as much of it as possible - through a series of puzzles and hazards.

Make no mistake, though: while the controls are simple, this isn't a simple game, and your obstacles quickly go from easy-to-understand seesaws and switch-activated doors to horribly complex puzzles where you have to coordinate several blobs of different colors at once.