We'd heard about the impending release of XCOM: Enemy Unknown earlier in the week, and true to their word 2K Games has launched the title today for iPhone, iPod touch and iPad. XCOM is as close to a direct port of the console and PC/Mac game as possible on an iOS device, and as such weighs in at a whopping 1.86GB. So grab a coffee while it's downloading. About the game:

Threatened by an unknown enemy, Earth’s governments unite to form an elite paramilitary organization, known as XCOM. As the commander of XCOM, you must create a fully operational base, research alien technologies, plan combat missions, and lead your soldiers in fierce battles against a terrifying alien invasion. The decisions you make will affect the fate of humanity. You are our last hope.

You'll need an iPad 2 and up, iPad mini, iPod touch 5th gen or iPhone 4S or 5 to play XCOM, and you'll need to drop $19.99/£13.99 to get your hands on it. We've not had a lot of time to check it out yet, but it looks incredible. Grab it now from the App Store and drop into the comments once you've played and let us know what you think!