Angry Birds turns two this weekend

Rovio's mobile smash Angry Birds is two years old on December 11, and the Finnish developer is marking the occasion in several ways.

First, a new update for Angry Birds, dubbed Happy Birdday, unlocks all episodes and adds 15 levels, plus new menus, graphics and achievements. In the US, retail chain Barnes & Noble will host special events and giveaways on Sunday between 11am and 3pm. Toys 'R' Us will offer 25 per cent off Angry Birds merchandise, and a code that unlocks a special level in Angry Birds Chrome.

In London, Forbidden Planet will also be marking the occasion. It will even be celebrated in Japan, where CMO Peter Vesterbacka will give a presentation at the Apple Store in Ginza, with a special event taking place in Tokyo's Harajuku.

It's hard to believe Angry Birds is only two years old: it's been downloaded 500 million times, is the most copied brand in China and has turned Rovio from a small Finnish developer into a studio valued at more than a billion dollars and comparing itself to Disney.