Playing Dual Survivor is the gaming equivalent of being punched in the stomach by someone who claims to be your friend. And, like the assualted party in that metaphor, it will leave you wondering if you somehow deserved it. But, even as your find yourself asking the question, you will realise that it's really the game which is to blame.

This oddly schizophrenic sensation is deliberate. The game demands an equal split of your mental energies. You have to navigate two seperate scrolling mazes on the same screen at the same time. The objects you're leading down these paths are two power disks destined to save a post-apocalyptic Earth (we don't ask how).

The tracks are colour coded, which lets you relax your vision a little and absorb the twisting and turning of each path simultaneously.

You need both thumbs on the screen at all times. Though things start off easy, with both paths taking identical routes, you'll soon find yourself having to do drastically different maneouvres with each disc. Within a few levels the difficulty ramps up significantly, with enemies, jumps, and route-altering switches all vying to end your run.

The level of difficulty in Dual Survivor is amplified by the controls. While the premise of the interface is fine - with the disks placed high enough on screen to avoid be hidden by wandering thumbs - playing the game on the iPhone screen is frustratingly fiddly. Move your thumb a shade too far from their designated spots and your discs will be left floundering without direction.

It is this lack of control that starts to really upset your already frustrated and shattered mind while playing Dual Survivor. Any lapse in control is almost impossible to recover from, and it sometimes feels that these lapses aren't entirely your fault.

So, while Dual Survivor's fun premise and brutal difficulty will probably keep masochists and genre fans swearing deep into the night, its controls may prove too unforgiving for some.