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) features not available on the smartphone versions. One day after the Windows version was released, the Mac App Store launched, with one of the first offerings being its own version of "Angry Birds". Ports of "Angry Birds" have also been proposed for the Wii and Nintendo DS systems, with the former becoming realized through "Angry Birds Trilogy" (see below). A 3D-enhanced version of the game was proposed for release on the LG Optimus 3D in October 2011. The popularity of "Angry Birds" has helped spread the game to other devices that were not initially designed as gaming machines. Barnes &