Plague Inc is a very pleasant unpleasantness.
This is the first game from Ndemic Creations, in which you play the part of a pathogen, and your objective is to merrily spread to all the peoples of the world, and then make them dead.
Play takes place on a map of Earth, where you press on a country to drop Patient Zero and watch as they (presumably) wander around touching people without washing their hands. As more and more people succumb to your germy creation, the infected areas bloom into a deep, biohazardy crimson. Boats and planes crisscross the world, possibly taking your infection with it. There is a real grim satisfaction in seeing the first little red plane jet from A to B, dragging behind it a red trail, spreading your custom pathogen to pastures new.
As more and more people become infected, you earn DNA points, which you use to evolve and mutate your disease in new and exciting ways. You'll need to make yourself more lethal if you want to achieve your goal of wiping out those pesky fleshbags. But it's here that Plague Inc reveals itself as a deeper strategy game than it appears at first glance.
As your disease gets more dangerous symptoms, more countries will notice it and work towards a cure. You can delay this with other upgrades, but those humans are a tenacious bunch. Finding and keeping a balance between infecting more folks and not being cured is a real stressful delight. I can't tell you how pleased I was when I managed to wipe out humanity with them just days away from discovering a cure. Distressingly pleased, in fact.
Different kinds of pathogen unlock each time you successfully bring about the end of mankind. Fungal spores, for instance, spread very slowly, and thus demand more evolutions of your transmission methods. The bioweapon is utterly lethal, so much so that the challenge comes from spreading faster than your hosts can drop dead.
Some will doubtless find that the subject matter makes them a little queasy, and that it is in poor taste to have a game where you must wipe out all humanity. To those people, I would respectfully point to Medal of Honor: Foreignerfighter and other games of its ilk, and say that at least Plague Inc does it's mass murder thing memorably and intelligently. Just look at those graphs(Plague Inc has excellent graphs)!
Plague Inc has achieved something that very few mobile games have done for me - making me want to keep playing it after I'm done on the bus or in the coffeeshop or waiting for my parole officer or whatever. If you let it, it gets under your skin and into your head like... well, like a virus.
Plague Inc is out now for Android (and iOS, if you can stand to put up with awful software like iTunes)