Killzone: Liberation is the handheld sequel to a first-person shooter that appeared on Sony's PlayStation 2 some years ago. It follows on from the action depicted in that game, casting you as Captain Templar, on a mission of 'CRITICAL IMPORTANCE' (ACCORDING TO THE MANUAL – PRESUMABLY THE CAPITALS ARE THERE TO EMPHASISE EXACTLY HOW CRITICAL THE MISSION IS IN CASE YOU MIGHT HAVE NOT REALISED FROM THE WORDS ALONE).

Like the original PS2 game, you'll take on the nefarious forces of the Helghast (who still look suspiciously like the Kerberos soldiers from Mamoru Oshii's movie The Red Spectacles). And like the home console game – in which it was possible to die during a cut-scene – it's a bit broken and distinctly average.

Unlike the home console game, it's not a first-person shooter. Instead, the action is depicted from an isometric, bird's eye view – almost overhead, but not quite. Nevertheless, proceedings are still fairly intense, and after a fairly undemanding introduction things get pretty harsh, quickly.

The basics of the game have you wandering around predominantly linear environments, shooting enemies by pointing vaguely in their direction till the auto-aim kicks in. The challenge here is not so much the accuracy of your shooting, but your use of cover, ducking behind objects and popping out when your enemies have exhausted their clips.

Occasionally you'll also have other squad members at your disposal – normally the arbitrarily swearing and stereotypically burly and Hispanic Sergeant Rico Velasquez. These sidekicks are controlled by activating the 'Tactical Command System' – pressing up on the D-pad – which slows the action to a near-standstill and offers you a selection of waypoints or action markers for you to send your troops. Or you can simply have them escort you.

As you go through the main campaign mode you'll pick up new weapons (including an incredibly pointless sniper rifle), and you'll get to drive round in hefty hovertanks or jump into gun emplacements. Playing through the campaign mode unlocks a series of challenges which, in turn, unlock special abilities to be used in later campaign missions, such as being able to carry extra grenades.

Killzone: Liberation is technically impressive, and initially the action is fairly entertaining, if a little routine. But after the first few chapters it starts to get niggly, even spiteful.

First, there's the targeting, which fails to work at too many critical moments. Then there's the weird and annoying vehicle controls, which seem to have been introduced simply to make driving and shooting more challenging. Instead of using the analogue stick to move, as you do on foot, you need to press face buttons to accelerate or decelerate, and the steering is oriented to the direction the tank's facing (so pressing left won't always turn your tank to face the left of your PSP screen). Finally, automatically triggered checkpoints can sometimes screw up your progress if, for example, you pass one just as your vehicle's about to explode, or if you've just run out of bullets.

Those are the niggles that conspire to make the game a bit more tedious than it would otherwise be. But when it's not just plain boring, Killzone: Liberation is spitefully unfair.

The fact that Captain Templar can only carry a single weapon means that if you run out of bullets it's basically game over, and you'll need to restart the last checkpoint. If you're outnumbered in the open, or by troops equipped with rocket launchers, it's basically game over, and you'll need to restart the last checkpoint. If the targeting fails, as it frequently does, while trying to shoot a spider-bot, it's basically game over, and you'll need to restart the last checkpoint.

The end result is a horrible stop/start staccato rhythm that's far from edifying, and the typical range of multiplayer modes do little to make up for it. It's not so much that there's anything drastically wrong with Killzone; it's just that there's not really anything drastically right about it either.