I just killed a man using a mixture of pneumonia and insomnia. Bio Inc. isn't your usual slaughter simulator. It's a puzzle game with a dark heart that's all about infecting a human body with the worst diseases money can buy.

It's an interesting experience. On the one hand you're pleased to succeed, on the other you've just injected a healthy man's respiratory system with the H1N1 swine flu virus.

Or you've sent him to the wrong doctor, fattened him up, or started him smoking. There are some decidedly unpleasant overtones here, and they make for an uncomfortable slice of mobile gaming.

There's the obligatory star rating system, and a surprisingly in-depth strategic core to proceedings too. You just have to get over the fact that you're butchering people for points.

Tap to infect

You control everything with taps. First you need to collect viruses and infections from the different systems of your patient. You can then spend these on more insidious conditions.

The main screen of the game shows whoever you're trying to kill on the right, and a list of their vital parts on the left. When one of the entries on the list flashes it means there's a virus there. Tap to collect it and you'll get some bio points.

When you've earned enough of these points it's time to do some damage. You head to a menu that's full of disease trees. The earlier ones, like high blood pressure, high cholesterol, and low potassium, cost a few points each.

But as you unlock new diseases, like angina, muscle spasms, and Crohn's, they cost more and more. You can attack a patient's immune system too, stealing their sleep and making them depressed.

Or you can add to the likelihood that they'll naturally develop certain ailments by starting them smoking, making them obese, and a variety of other generally unpleasant things.

Sick bag

All the while you're doing this rival doctors are trying to keep your bag of diseases and ailments alive. They'll be fed drugs, given treatment, and when things get really bad taken into intensive care.

It's your job to reduce the systems keeping them alive down to 0. The lower they are, the more likely your victim will develop other awful things. It's all represented by lesions and gory smudges on the skeleton you're collecting points from.

There are a huge number of different patients to play with, and each has three different difficulty settings to tackle in order to get better rewards.

To start with you're infecting the infirm and the sickly, but the game ups the challenge as you go along, giving you stronger and stronger immune systems to try and turn into wibbling jelly-based mush.

Gurgling noises

Considering where to spend your bio points adds a layer of strategy to the game. Do you attack the fat man's circulatory system or try and make him more susceptible to disease by taking down his immune response?

But therein lies the cruel heart of the game. We're conditioned to feel good when we finish a level. Here finishing means we've reduced another human being to a bubbling mess of broken organs and shattered bones.

It's a grim thought, and one you'll be having often during your playthrough. There's fun to be had here, but it's forever tempered by just how bleak the subject matter is. Things can get a little repetitive as well, especially in the early stages.

Still, Bio Inc. has an interesting, if icky, central idea. And discovering the different ways you can kill a healthy human with a combination of diseases, incompetence, and life-style changes is strangely compelling.