Angry Birds (video game) was being played, the staff liked the characters, and the team elected to design a game around them. In early 2009, physics games, such as "Crush the Castle", were popular flash-based web games, so the Rovio team was inspired by these games. During the development of "Angry Birds", the staff realized the birds needed an enemy. At the time, the "swine flu" epidemic was in the news, so the staff made the birds' enemies pigs. Angry Birds was the studio's 52nd produced game and on its initial release, the game did not sell many copies. After Angry Birds was a
Angry Birds (video game) device, and Apple's iPhone and iPod Touch mobile digital devices, Rovio has released versions of "Angry Birds" for additional devices. An iPad-exclusive version, "Angry Birds HD", was released with the iPad mobile digital device in April 2010. In August 2010, "Angry Birds" was made available to the Palm Pre phone running Palm's webOS operating system through its App Catalog online store. Symbian^3 phones received a version of the game in October 2010, which initially includes only the "Poached Eggs" and "Mighty Hoax" episodes. Angry Birds works on Kindle Fire and Kindle Fire HD. In May 2010, Rovio announced plans for