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) for any unused birds. Upon completing each level, players receive one, two, or three stars depending on the score received. Players are encouraged to repeat any previously beaten levels in which the full three stars weren't awarded in order to fully master them and earn the full three star rating. In early 2009, Rovio staff began reviewing proposals for potential games. One such proposal came from senior game designer Jaakko Iisalo in the form of a simulated screenshot featuring some angry-looking birds with no visible legs or wings. While the picture gave no clue as to what type of game