Plague Inc is a disease simulator that tasks you with wiping out all human life on Earth with an impressive variety of customizable diseases.
Gameplay revolves around choosing Symptoms, Transmissions, and Abilities to develop your chosen plague over time to ultimately infect and kill the entire population of the world. You can either choose one of the (currently) 11 plague types, or play one of a series of scenarios. In the former, you simply choose the difficulty level and start evolving your plague; the official scenarios introduce a different level of challenge by changing the conditions of the game, e.g., by removing sea travel between countries as a way of spreading your plague. In both game types, you start off in a single country with a single host, and have to race the clock to infect and kill all humans before they find a cure - or before your plague kills all its hosts! Each new country you spread to awards you DNA to spend on upgrading your plague, and you also receive DNA as you infect or kill more people. How you allocate this, and when, will determine your success in the game.
The game is cleverly designed, and each plague type feels different in the way you develop it and the strategies you can employ. Some, like Bacteria and Virus, require you to balance your plague's infectiousness and deadliness to win; others, like the Necroa (zombie) and Simian Flu allow you to develop armies that you can move and upgrade to spread the disease and kill humans. Though simple, there is a lot of room for experimenting between different plagues and strategies, which gives the game a lot of replay value.
These have been adapted well from a touchscreen mobile game to the Xbox controller. Moving between pick-ups is smooth and navigating the in-game menus or speeding up/slowing down time is very intuitive.
The audiovisual design is pretty basic, but effective. The screen is a world map, with colored dots and lines showing you the carriers of your plague and their travels to other countries. The sound is unobtrusive: there's not much in the way of music, though there are occasional sound effects. There is also an in-game news banner, which presents game-related information, such as whether your plague has been detected, or the response of different countries; game events, many of which are tied to achievements; and humorous items and pop culture references. It's a small touch, but it gives the game extra personality, especially early in the game when you are waiting to collect enough DNA to develop your plague.
The game has a huge number of achievements, most of which are related to unlocking specific symptom combinations, or triggering particular events in the game. There are great guides and an excellent walkthrough on TA to help you, but be warned - the game relies on RNG, so it may take multiple attempts to get a solution to work for you. Completionists should also be aware there are three achievements in the main game that will take quite a bit of time and persistence to unlock: you have to get the highest score rating in three scenarios with each of the eleven plagues on at least medium difficulty. There are also achievements for winning with each plague on the highest difficulty. Expect 60-80 hours for the base completion.