In Steven Soderbergh's 2011 movie Contagion (spoiler alert), Gwyneth Paltrow essentially kills several million people by not washing her hands. It's dark, depressing and very, very good. Spend a few hours with Plague Inc, though, and you'll be seeing things firmly from the microbes' point of view.
The object of this fiendishly tough strategy sim is to evolve an organism that will spread around the world, killing everyone it infects and ultimately ending life on Earth. We're not in Peppa Pig's Party Time now, Toto.
It's easier said than done, though. As your disease spreads from person to person you gain DNA points, which you can then use to level it up. You do this in one of three areas – making it either more contagious, more deadly, or more difficult to cure. But be careful: make it too deadly and it'll kill the host before it spreads. Make it spread too quickly and it'll attract too much notice, leading to a cure being fast-tracked. And so on.
Plague Inc is an incredibly detailed game, with several different plague types to develop, from the simple bacteria through the impossible-to-spread fungal spore all the way to the brilliant Neurax Worm.
Each have different strengths and weaknesses, so you'll need to plan your strategy carefully from the start. Set a virus loose in a humid part of the world and it'll be spreading in no time, but also spotted quickly. Do the same with a fungal spore and you'll probably still be stuck in one country an hour into the game.
Various symptoms will also have unpredictable effects in different environments, especially when combined with other traits: evolve a disease that causes both haemophilia and skin lesions and you'll see what we mean.
With three difficulty levels and regular updates (hurry up with the zombie version, please!), there's no shortage of replay value with Plague Inc either; just hope you finish it before it happens for real.