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 "Bad Piggies: Egg Recipes", along with doodle books based on some characters of the game. After a few weeks of the release of Angry Birds Space, they also released Angry Birds Space books about numbers, alphabets, and stickers. On 20 March 2012, "National Geographic" published a paperback book titled "Angry Birds Space: A Furious Flight Into The Final Frontier" shortly before the release of "Angry Birds Space" which became available on 22 March 2012. National Geographic also has a book titled "Angry Birds Feathered Fun" for learning all about birds. In the same year, Rovio created a contest with the