The world is on the brink of Armageddon. A full-scale global thermonuclear war has broken out, and as a general in a bunker somewhere, you must direct your offensive and defensive systems to nuke your opponents. Nobody wins, but maybe you can lose the least. Everybody dies.
DEFCON is an online multiplayer strategy game, but it can also be played in a singleplayer mode. Players place units, such as missile silos, airbases and radar dishes, on their territorial maps, and the game counts down from DEFCON 5 to DEFCON 1, during which time the players are to make strategic choices to eliminate their opponents without losing too much themselves.
The gameplay is shown on a large world map and the action is represented by icons and lines reminiscent of the drawing style of their two previous games: Darwinia and Uplink.
DEFCON is probably inspired by Wargames more than anything else (the movie and it's videogame adaptation). The game's look as well as text on the main menu are direct references to this.
Sound
DEFCON applies a bunch of casual sounds to heighten the psychological effect of dealing with a thermonuclear war. Among these, the background music stays very much in the background. However as the game approaches the Defcon 1 stage, the background music increases in both tempo and strength. During actual nuclear war, piano key strikes can be heard as nuclear warheads impact with cities.