With Rage HD, John Carmack has rolled up his sleeves, placed a huge bicep on the App Store table and flexed. "This is what I can do with iOS4," the famous co-founder of id Software is saying, "this is how good iPhone games can look." He's not wrong, either: Rage looks outstanding. Strolling through the dank corridors of the Mutant Bash TV set reveals cracked, graffiti-stained walls and blood-soaked floors peppered with rotting chunks of flesh. Light from the apocalyptic outside pours through huge windows, casting ominous shadows and highlighting the detail on the gnarled faces of mutated enemies.

Rage might well be the best looking mobile phone game ever, but ultimately it's little more than a glorified tech demo; a portable prelude to id's main event next year. It's a half-hour rollercoaster ride of blood, grime and guns, but little more. This is a shooter on the iPhone after all, a touch-based device that - no matter the pedigree of the developer - will never lend itself fully to the genre. That said, the game handles as well as any its mobile contemporaries, but unfortunately that happens to be not very well at all.

Considering its disposition as an on-rails shooter, navigation is handled automatically. Aiming and shooting is left to the player, however, and this is where problems begin to surface. Swiping a finger across the screen will move the camera, or alternatively you could take advantage of the iDevice's gyroscope, tilting the gadget to move your crosshair about the screen. Aiming is difficult, to say the least, with fingers and thumbs obscuring the action all too often.

If you do manage to get an enemy in your sights, a quick tap of a button in the bottom right corner will bring your gun to life with a blaze of bullets. Geysers of blood let you know whether you were on target or not, in addition to prize money you'll be rewarded with should you make the kill.

Each of the three levels in the game are portrayed as TV episodes of Mutant Bash TV; a twisted game show in which contestants are furnished with pistols, shotguns and AK-47s and then thrown into environments with hordes of bloodthirsty mutants. As you fight for your survival, the show's maniacal host, J.K Stiles, laughs and jeers, getting sadistic kicks out of the bloodsport. It's not much of a story, but it contextualises the violence just fine, offering an insight into the post-apocalyptic world of the full game.

Although the aim of the game is survival, you're also playing to rack up as much cash as possible - this is a game show after all. Each level is packed with wooden targets and wads of cash - or 'Bash Bux' as they're known. The bigger your bankroll by the end of the level, the better your grade - but there's not much of an incentive to improve this. Given the score-based nature of the game, Game Centre or OpenFeint support would have been nice, but there's nothing of the sort to be found. Seeing all there is to see in Rage takes less than half an hour, but other than showing the game off to jealous Android owners, there's not much of a reason to replay any of it.

Rage might well be short, shallow, and shoddy in the control department, but it's still well worth the price of admission. For a mere £1.19 you get a medley of high-poly character models, impressive animations and the best textures the iPhone has ever seen; a glorious glimpse into the future of gaming on phones.