If ever there was a movie which begged to have a video-game franchise, WarGames would be high on that list. The very premise of the film, global thermonuclear war and the destruction of mankind, screams out for digital replication, so rejoice as it has finally been realised, albeit very unofficially, in the guise of DEFCON from Introversion Software.

The aim of the game is to cause as many casualties as possible to your enemies, whilst defending your own installations, cities and civilians from destruction, radiation and third-degree burns. The game travels a very easy to follow path; pick a country, choose online or single player with AI and start the inevitable demise of society. Each war is played against a timer, which as it ticks by, changes the DEFCON level from five to one automatically; this dictates the actions that can be performed at that time.

The scenario is played out on a very stylised world map, which clearly mimics those at the headquarters of NORAD. Everything is bright and simple, making it easy to get an overall view of what is happening in the theatre of war.

Every country has the exact same number of units available to defend its interests, regardless of its size. When playing as Western Europe, this area is relatively easy to defend, but playing larger areas, such as the USA, means units are scattered and isolated. It makes the game feel a little unfair given the size of the military budget.

At DEFCON 5, the limited number of radar stations, missile silos, air bases and naval fleets can be placed on the map. Fleets can be moved in international waters, but no hostile actions can be taken. Moving to DEFCON 4 activates radar stations, showing any hostiles in range. Player units can still be placed, so not deploying everything at DEFCON 5 is a good idea, leaving some room for flexibility.

When DEFCON 3 and 2 are reached, air and naval units can be used to attack the enemy, but only by conventional means. It’s at DEFCON 1 that the nuclear strikes can begin, and the slip down the steep slope of assured obliteration accelerates exponentially.

As the war unfolds, the player can use any of their available forces to cause pain and suffering. Air bases have fighters and bomber units, giving intercept and destroy options, and also some additional nuke strikes from the air. There are three naval unit types: battleships, subs and aircraft carriers, which can make fleets of up to six units. There is some degree of strategic element in the organisation of these; subs are vulnerable to battleships, but can also stay well hidden and move unhindered to enemy coastlines for short warning strikes. Battleships are vulnerable to aircraft strikes but can defend aircraft carriers.

Radars allow the player to see what’s approaching the defended air and sea space. Taking these out makes gaps in detection coverage, so air units can be sneaked through avoiding as much anti-aircraft fire as possible. Missile silos act as both defensive and offensive units, but can only be used in one capacity at a time; launching the nukes from silos can’t be done immediately, as they require priming for two minutes before they launch, so timing launches is important as a destroyed silo is a useless silo.

Whilst it’s very easy to select and move units, it’s not possible to build new installations at all. DEFCON is not about the micromanagement of building an empire; it’s about destruction and the pummelling of civilisation to the ground. The polished and slick interface makes this simple to achieve via the mouse, allowing the launching of nukes, and the deaths of another few million, with just a couple clicks.

Selecting the silos and ICBMs changes the cursor displaying the number of missiles left. Click on the city to annihilate and sit back and watch death swipe his scythe. When the nukes strike, there’s a white glow, and the number of casualties is displayed on screen, 20 million, 60 million, 80 million... the numbers are clinical and detached; destroying Moscow and Leningrad just a blip on a world map. It feels almost too easy giving a sense of bleakness; it's unsettling that nuclear war is just a matter of totalling up the figures.

The whole feel of the game is very much that of an overseeing general commanding the war effort from a safe impenetrable bunker, counting the deaths and speaking of collateral damage, aloof and dispassionate, wielding an enormous amount of power in his decision making. Sadly then, that DEFCON’s main issue is the lack of depth.

The rigid game structure limits the number of usable strategies; it’s a case of timing nuclear launches, using subs for surprise attacks and hitting the most vulnerable targets. Place units, blow stuff up, end of game, particularly in the solo play. However, the real fun is to be had in the destruction of real-life opponents online.

Adding to the mix is the ability to form alliances. Via the simple text chat interface, the most cunning and worldly can influence the game massively. As with real world politics, it’s possible to create secret deals, concocting co-ordinated attacks and then stabbing the unsuspecting ally in the back with that fleet of subs he thought were there to support the joint invasion. It’s here in multiplayer that DEFCON works best, removing the shallow AI of the single-player game.

The online modes are all similar, but there are quite a number of them to choose from in the lobby. The default mode works the same as the single-player game, scoring points for nuking opponents’ cities, things get slightly quicker in Speed DEFCON when the game takes no longer than fifteen minutes to complete, runs at the highest speed available and can’t be paused, perfect for those quick skirmishes during a lunch break.

As if the planet wasn’t big enough already, the “Bigworld” mode makes things twice the size. Each unit is half its normal size, has half the radar range, has half the weapon range and takes twice as long to move anywhere. Games played in this mode can take eons to finish.

Scoring can also be changed to one of three modes, which makes quite a difference to the strategies employed. By default points are scored for every kill, and lost for every casualty. In genocide, points are scored simply for every kill. More interesting is survivor mode, where points are scored for every survivor in the controlled territory. Everyone starts with 100 points and the score can only go down.

Of all the different variations, perhaps the most appealing of these is the diplomacy mode, where all players start in one big alliance. This changes the "first-strike feel" into much more of a cat and mouse game. Are alliances being formed? Who will initiate the offensive action? Is it best to get in there before anyone else?

DEFCON is great for a quick bash at Mutually Assured Destruction; it really exudes that mimicked 1980s WarGames feel extremely well. Longer term it’s a case of nuclear winter, as the game says, everybody dies.

So, how about a nice game of chess?