Nestled in amongst the studio logos and copyright messages as you boot up Ratchet & Clank: QForce is a logo proclaiming 2012 to be the 10th anniversary of the sci-fi odd couple. The series has averaged one game a year across its decade-long lifespan, with the clumsily titled QForce marking the 11th outing for the quick-witted lombax and his mechanical pal.

Most game series have run out of steam after reaching this milestone, with the sort of 3D platform romps that Ratchet and Clank inhabit proving especially susceptible to the rigours of age. Perhaps that's why Insomniac's most recent entries have felt a little... desperate. Between last year's limp and chaotic co-op scramble All 4 One and QForce's attempt to inject mob strategy into the series, it seems confidence in the characters' core appeal is at a low ebb. QForce is a platform game that's apparently terrified of being a platform game.

Instead, it's a tower defence hybrid, and a sadly clumsy one at that. Each level is now a self-contained maze with a mass of generators at one end. If the enemy destroys all of these, it's game over. Access to this area is down two linear pathways, along which are scattered fixed points where you can place turrets, mines and barriers. Periodically, waves of enemies start marching towards your position and you must repel them by any means necessary.

Weapons level up with use, with three tiers of increasing power to unlock.

So far, so predictable. However, you need to be a bit more proactive than simply fortifying your choke points and waiting. In between attacks, you need to venture out into the level to accomplish a variety of tasks. Your main goal is to activate the key nodes needed to reboot the planetary defence systems for each world. Doing this means running a gauntlet of various enemy types and destroying a series of shields.

The problem is that you start each level without any weapons other than your trusty wrench, and so must also scout around the level seeking out weapon pods to gain access to such tools and gadgets as the Warmonger, Thundersmack and other familiar arsenal items from previous games.

You're also on the lookout for crates that can be smashed in order to earn the nuts and bolts required to purchase the various defences for your base. These accumulate slowly - a good foraging expedition generally nets around 5000 - and since the most effective turrets and barriers cost at least several thousand each, it takes several rounds to set up even a basic defensive line.

It's not as if these expensive defences are particularly robust. Barriers crumble quickly and turrets seem to take more damage than they can dish out. The inevitable result of this is a constant back-and-forth as you abandon assaults on enemy positions or the hunt for a new weapon pod in order to dash back to base - through often confusing layouts - in order to do the job of fighting back yourself. Even then, you'll find yourself rushing from one side of the base area to the other, covering both entry points and bashing crates to restock on ammo and health, rather than relying on your feeble automated defences.

You can use rocket boots to get around faster, but at the cost of precision control.

The tower defence genre has always rested on a bedrock of frantic plate-spinning, but QForce takes it to a ludicrous extreme, spamming you with tough enemies, limiting your resources and generally making every inch of progress in the game's disappointingly thin story feel like more trouble than it's worth. This is a ferociously difficult game, but one that rarely feels like it's playing fair. Too often it seems to be punishing the player for stopping to think, exploring too far or simply trying something different.

If you're playing solo, that is. After the lukewarm reception that greeted All 4 One it's understandable that the co-op element has been downplayed for this entry, but that doesn't make it any less of a multiplayer game. With two players, either playing locally or online, things come into better focus. One can venture forth into the level while the other guards the base, or both can assault different enemy key nodes at the same time. More to the point, with two players in action accumulating currency, it's possible to stockpile bolts, establish a solid defensive line of turrets and engage with actual strategy rather than being constantly forced onto the back foot.

The game is more satisfying in co-op, but it still never really finds an enjoyable rhythm, the solo platforming and combat forever interrupted by the tower defence element rather than working in harmony. Third-person action and tower defence can work - see the superficially similar Orcs Must Die! - but QForce's clumsy genre patchwork feels more like an awkward attempt to latch onto a popular gameplay mechanic rather than an organic direction for the series to take. The steep in-