Angry Birds maker hails shift to mobile

Peter Vesterbacka is the man behind Angry Birds. Produced by gamemaker Rovio, it has been the number one app in the UK for the past year and leads the charts in 70 other countries. To date, the game has been downloaded over 75 million times worldwide. He talks to Mary Watkins, technology correspondent, about the gravitational shift to mobile technology and the formula for making a winning app.