Angry Birds (video game) featured app on the UK App Store in February 2010 and quickly reached No.1 there, it reached the No. 1 spot on the paid apps chart in the US App Store in the middle of 2010 and then stayed there for 275 days. The initial cost to develop "Angry Birds" was estimated to exceed €100,000, not including costs for the subsequent updates. For the iOS version, Rovio partnered with distributor Chillingo to publish the game to the App Store. Chillingo claimed to have participated in final game polishing, such as adding visible trajectory lines, pinch to zoom, pigs' grunts, birds'
Angry Birds (video game) hits of 2010". In December 2010, in honor of the one-year anniversary of the release of "Angry Birds", Rovio Mobile announced that the game had been downloaded 50 million times, with more than 12 million on iOS devices and 10 million on Android. By January 2014, the "Angry Birds" series had reached 2 billion downloads, including "Angry Birds", "Angry Birds Seasons", "Angry Birds Rio", "Angry Birds Space", "Angry Birds Star Wars I & II" and "Angry Birds Go!" On Christmas Day 2011 alone, 6.5 million copies of the various "Angry Birds" games were downloaded across all supported platforms. In the