Tower defence games are notorious for being challenging - the good ones, anyway - and Kingdom Rush fits the type.

Thankfully, it's as hard to put down as it is to play. However many times you fall flat on your face - and there will be many - you'll want to carry on.

This is partly thanks to the world developer Ironhide has built Kingdom Rush in - as the name suggests, a mock-mediaeval setting that as much worships your average fantasy novel as pokes fun at it.

King of its castle

Not only does this allow Kingdom Rush to employ a slew of inventive enemies to take down - everything from fully tooled-up knights to impetuous demons - but it also adds a vital sense of character.

Indeed, the game's cartoon-esque visuals are coupled with soundbites that serve as constant reminders of Kingdom Rush's intentionally jocular tone: almost every action you take is accompanied by a line of speech or sound effect that keeps your spirits up, even when you're in the heat of battle.

It might sound like a small point, but this sense of fun helps to ensure that Kingdom Rush never becomes overwhelming or tedious, despite being a tough and more than usually hands-on approach to tower defence.

Fire and fury

As well as planting towers in any of the levels' designated spots - those hosting artillery, arrows, guards, and wizards all on offer - Kingdom Rush also allows you to bolster your efforts at short notice with bonus troops and fireballs.

Such power-ups are designed to be dropped in at the last minute, plugging any weak spots in your line until you can plant a tower nearby or upgrade those already in place.

This constant battle between trying to get ahead of your foe's waves of attacks and reacting to sudden changes in its approach is the core of Kingdom Rush's gameplay: more than any other game in the genre, there's a particularly fine line between success and failure here.

On the edge of glory

While failure is never far away, at the same time anything seems possible. Switching just one tower for another can completely alter the outcome of a level, making Kingdom Rush a very fluid battle simulator, rather than one defined by a limited number of rules.

Add to this the variety created by your enemy - full-on boss battles often popping up during the final wave of attacks, with huge hulking beasts recalling platformers of old - and Kingdom Rush has the power to keep you on your toes from beginning to end.

Of course, that's a trait shared by several other tower defence titles. Where Kingdom Rush is able to pull ahead is the sense of fun that's been built into its approach at the same time - a rare combination of frustration and frivolity ensures this is one kingdom you'll be in no rush to escape from.