Pandemic is the name of a series of flash games available on the internet. The theme of the game is disease, and the object of the game is to destroy humanity. The game is set up somewhat like the boardgame Risk, with a map of connected geographic areas. The disease begins in one of them, and with the player's prodding, spreads throughout the world, spread by land, air and sea movement. The governments of the world fight back against your disease by trying to find a cure, or by closing borders so the disease can not spread.
This is one a subgenre of flash games where the player has very little direct control over the game. It is quite possible to start a game, tab away from it, and come back to see how your hardy little pathogen is doing. The main gameplay consists of evolving ways for your pathogen to spread to different environments, and deciding in which way it will kill people. One of the challenges is that a disease that is lethal and contagious is also quite visible, causing your pathogen to be quarantined before it can infect the planet.
This game is also responsible for the meme of Madagascar and its closed ports. In the game, Madagascar can only be reached by ship, and when the nation closes its ports, it becomes immune to the disease. Many a game ends with everyone in the world dead, besides the untouched island of Madagascar.
In general, I find this game to be an absorbing and atmospheric game, especially with the sinister, looping music. However, as a game, it doesn't have much diversity or challenge in gameplay. I first played it on a very depressing day, and was quite enthralled to forget my troubles in watching the world laid waste by pestilence. However, it quickly lost its interest for me.
http://www.pandemic3.com/
http://knowyourmeme.com/memes/shut-down-everything