Unlike the paid for version of mobiles most successful games, Angry Birds on the Android platform is Free.
Advertising is used to pay for the 'free' version with appearing throughout the game. Rovio have said they're making over $1m a month from the add support version.
Over 8 million Android versions have been downloaded and that number rises daily.
The new Christmas 'Seasons' version has been released and it's free to anyone who purchased the Halloween version.
Next year Rovio promise to add PlayStation 3 and Xbox 360 versions of the hit Birds vs Pigs puzzle physics video game.
