There tend to be two main schools of thought when it comes to naming video games. One is to use a blunt, macho sounding single word title – like Quake, Rage, Halo, Prey or Fracture for instance. Or you can go the other way and add a gigantically long, and utterly meaningless, subtitle – Legends of the Ancient Evil of Doom or some such. But a third option is to go home early and just make do with whatever bland, least evocative sounding name first comes to mind.

Unfortunately THQ has opted for the latter here, which is a great shame because with a rubbish name and no marketing Lock's Quest can only wistfully dream of reaching the heady heights of cult classic.

It's particularly a shame as this is one of the most ambitious and imaginative games ever on the DS – particularly from a western developer. 5th Cell, who also did Drawn To Life, seems destined for great things if it continues at this pace. Not only do its games assiduously avoid the usual pigeonholing and clichés of more workaday titles, but they're getting noticeably better each time.

This one is part role-player, part real-time strategy as you take the role of Lock the apprentice archineer, who's drafted in to fight a losing war against hordes of magical robots called clockworks.

Lock's Quest uses an always-attractive isometric viewpoint that makes good use of some bright and well designed 2D art. At first it gives every impression of being a standard role-player as you take on the role of your stock 'chosen one', chat with your precocious younger sister and get remonstrated by your gruff but loving grandfather.

At the point at which some manner of turn-based battle should hove into view though the game's true nature is revealed. It turns out Lock has a knack for building things using a magical power called Source. This allows you to construct walls, turret, traps and helpers which you have to deploy in the game's many long siege battles.

Each battle is divided into three or more days, with each day split between a Build and Battle phase. During the Build phase you're free to lay down whatever buildings you can afford (additional Source is harvested from downed enemies). Typically this will involve building walls around the Source well or other object you are protecting and then setting up other towers and traps to funnel the enemy away from it.

During the Battle phase you have full freedom to run around the map wherever you like, repairing damaged buildings (by ratcheting a simple tool left and right on the touchscreen) and taking on individual enemies. The latter involves a different mini-game depending on which super move you are currently powering up, with simple stuff like pressing numbers in sequence or rotating a dial in a particular direction. You don't have much health but it does regenerate quickly, encouraging quick hit and run tactics on problem areas, rather than turning everything into an action game.

With dozens of enemies on screen at once and a pleasing variety of objectives and missions (there's a whole separate sub-game based on 5th Cell's earlier mobile game Siege), on paper this gets everything right. In practice, though, things don't run nearly that smoothly.

The first obvious problem is the poor controls. Everything is handled via the touchscreen and although all the different actions and mini-games are fine, controlling Lock himself is a constant hardship. The game tries to mimic the same system as The Legend of Zelda: Phantom Hourglass, but the pathfinding is dreadful and you seem to snag on every corner you pass. Even clicking on a building or enemy that's right in front of you often seems to confuse the game – sometimes you'll move right to it, sometimes to something else nearby or sometimes your tap won't even register.

The other main issue is that as pretty as it is, the isometric viewpoint really doesn't help when trying to lay down watertight lengths of wall. It's all too easy to miss a gap or misjudge an angle, which wastes pressures seconds as you rush to set up your defences. These problems mean that both main phases of a battle have a constant underlying air of frustration, as your in-game actions frequently fail to match up to your intentions.

But it's a tribute to the appeal of Lock's Quest that it still manages to entertain despite these issues. In part this is due to the sheer volume of content on offer, with a long (perhaps too long) single-player campaign and an excellent two-player combative mode. It seems likely that most of the control problems are largely due to the limitations of the DS itself, rather than 5th Cell, but either way it's going to be very interesting seeing what the developer comes up with next. (And let's hope the name does the content justice, at least.)