Who wouldn´t want to eradicate humanity from time to time?
If you say "Yes, here! Me!" then you should probably get some help.. or this game.. maybe both.
Either way, Plague Inc: Evolved is a simple game, where you can evolve your virus/bacteria etc. from a harmless flu to a pandemic mass killer.
While the base game is very easy but fun, Plague Inc. has so many different scenarios, as well as different Plagues from mind controlling worms, zombies, intelligent apes and so on, that you can destroy humanity again and again and have different playthroughs. Beside the bigger changes the ways you customize your sickness offers great replayability.
Last but not least the workshop provides hundred fan made plagues for your pleasure and humanitys demise. Furthermore a multiplayer mode is in the making and the developer is very actively improving the game time and time again.
Conclusio: Even if you know the game from it´s mobile beginnings the PC version is worth it´s money, with a broad array of possibilities and challenges to casually destroy humanity in a relaxing evening session.