Plague, Inc is a strategy game where you must mutate diseases and use them to destroy the world. The goal is to infect as many people as possible. There are multiple diseases in the game, each with their own outbreak strategy and the game is realistic enough that the developers were once invited to speak at the CDC. The developers have added plenty of expansions over time. The game also comes with save and load game functionality for multiple files so you can play many times at once. It’s one challenging game, but one that’s also worth checking out.