Quantum Conundrum's elegant first-person puzzling is only marred slightly by one very obvious comparison, but it's unfortunately something that this downloadable title never really manages to get away from.

I'll just say it and get it over with: Portal. Quantum Conundrum doesn't share its aesthetic or core mechanics with Valve's seminal work, but there's a clear influence in its vision and execution that the game simply cannot avoid. Partially that will be due to the involvement of original Portal lead Kim Swift, who will probably never be able to escape comments about cake or questions about GLaDOS for the rest of her life. Yet it is easy to respect her for not shying away from doing what she does best with Quantum Conundrum, and the fact this game - clearly produced with a fraction of the resources and a less generous development window - doesn't come off too badly when compared against one of the very best games in the history of forever should probably be seen as a positive.

So, yes, Quantum Conundrum isn't as good as Portal. Or Portal 2. It doesn't have the broad scope, that breadth of vision, those impossibly wonderful characters or that rich elegance of design. Much of your time playing Quantum Conundrum will be spent thinking about Portal - look, I'm thinking about Portal right now - but at the end of the day there's some canny and inventive puzzling within Quantum Conundrum that's worth enjoying on its own merit.

While much of the game's structure is certainly familiar - you move from room to room solving environmental puzzles that require the use of a central conceit, and are fed snippets of dialogue after each successful resolution - the game's gimmick is that it allows you to manipulate elements of weight, time and gravity by flicking your mansion environment through four specific dimensions. The first one you encounter is known as the Fluffy Dimension, and here the screen gets bathed in a blue hue and all items get turned into feathery white cushions that (and this next bit is important to the puzzles, by the way) weigh very little and can be picked up and chucked for miles. Later you unlock the self-explanatory heavy dimension, and there's a genuine satisfaction to be found from the tactile oomph of the first time you shatter a glass window by flinging a pillowy safe and transforming it mid-air into a very weighty brick.

While there's some clever content to be discovered, the pace of the first 90 minutes is certainly leisurely, throwing you through what feels like an extended and largely unwanted series of expositionary devices. Eventually Quantum Conundrum comes off simmer and the puzzles do a much better job of making your brain boil, though thankfully the game - which clocks in at a good pace of about six hours if you're as stupid as me - never becomes difficult and obtuse to the point that you'll need to be looking up YouTube walkthroughs.

It's a bit of a faux pas to discuss specific solutions in a game where the pleasure is derived from figuring them out by yourself, but there's certainly some good moments to be had. I was especially fond of one puzzle about half-way through the game, and I'm trying to keep this description as obtuse as possible, where you have to fiddle with time to catch a lift on an object that you have just thrown. And the first time you solve a devilish puzzle by flipping gravity is another euphoric moment.

The shine wears off outside of the mechanical excellence of some of the puzzles, sadly. The biggest weakness is in its aesthetic, taking place across the colourfully indistinct Quadwrangle Mansion, a lifeless environment with its only real charm oozing from the fact its many repeating portraits change as you flick through the various dimensions. Your companion throughout these cartoon corridors is Professor Quadwragle, voiced by John 'Q from Star Trek' de Lancie, whose distinctive vocal chords chip in a fairly good performance even though I get the impression Airtight Games didn't have the budget for some (necessary) multiple takes.

There are some nice ideas, though: I like how you play a child, and a viewpoint close to the ground gives the mansion an interesting sense of scale. Upon death, too, the game (which, by way of another presentational failing, can't quite seem to work out if it wants to have a hidden mean streak or not) adopts a dark and occasionally amusing tone to tell you one of the things in life the child will never get to accomplish, such as firing his first housekeeper. Actually - forget the boy, I'm almost 26 and I've never even had a housekeeper let alone fired one.

Wait a second! I've managed to go six whole paragraphs without mentioning Portal, which is a happy coincidence because once you get stuck into the finer parts of Quantum Conundrum your memories of Aperture do start to dissolve away. But they will always come back. Quantum Conundrum is a fine adventure with a mechanically competent series of puzzles, and I definitely recommend it, but while the game has got plenty of brain it doesn't have nearly enough heart.

Version Tested: PC