The Black Death is one of the greatest disasters ever to have befallen mankind. Claiming an estimated 75 million lives, it killed more people than Hitler, Stalin, and Winston Churchill put together, and it's thought to have denuded Europe of between 30 and 60 per cent of its population during the 14th Century outbreak alone. Eat your heart out, WWII!

The creative avenue for making a game about the Black Death has been closed until now, but with the coming of Will Wright's Spore we know it's possible for a video game about bacteria to sell – and what is the Black Death if not a highly infectious disease arising from the transmission of yersinia pestis, a bacterium.

Black Death Mobile places you in the shoes of said bacterium - drawn as a cartoon and affectionately entitled 'Pesty' - and starts you off in the bloodstream of a rat.

Using the '4' and '6' and '8' to brake you have to navigate to shallow veins close to the surface of the rat's body and then look out for the tell-tale interior signs of flea bites. Once you've found a likely spot, all you have to do is wait for a little proboscis to poke through, guide yourself as close to it as possible, and press '5' to get sucked up into the little flea's body.

Level Two. Unlike certain flukes and parasites, you're unable to control the behaviour of your host. There's still work to be done, however. The flea is a greedy insect, and it's likely to make several more visits to the rat-buffet before settling on a human. Every time it stops to feed, you need to repel an onslaught of rival bacteria. This part of the game is like Space Invaders.

Finally, you meet a human host, and this is where things get really interesting. After squirming down the proboscis, you need to start killing your new host. Why? Why not! You're only little, but there's strength in numbers, so you start multiplying as rapidly as possible.

Initially, this takes the form of a Bust-a-Move clone in which you need to fire copies of yourself at other copies of the same colour. If you bring three or more together, the matched cluster disappears and starts a colony elsewhere.

Once you clear a certain number, the screen splits and you have to play two games simultaneously, controlling the top with '1', '2', and '3', and the bottom with '4', '5', and '6'. After reaching another target, a third game begins, controlled with '7', '8', and '9'. All the while, it's possible to unlock bonus pockets of sepsis, while a ceiling of antibodies constantly shuffles your coloured clones downwards.

Inevitably, your diabolical work has symptoms on the outside, and soon the doctors are on the case. Fortunately, nobody's discovered penicillin yet, so the only treatment available to the hapless medics is to lance the buboes that your spread has created.

Every time a buboe is lanced and swabbed with antiseptic herbs, a line of antibodies appears through a small hole at one side of the screen and snakes along a swirling groove. You control a turret, and you have to fire like-coloured globules of infection to make fend the antibodies off.

You know, like Zuma.

Eventually, your internal rampage has done its job. Your host is dying. Before sepsis carries him off, however, you've got one last thing to do: get into another flea. It's time once again to find a shallow vein, identify a likely spot, and get sucked into another flea's tummy so the miraculous circle of Black Death can begin anew.