Angry Birds (video game) crates and rocks are incorporated into the structures, and power-ups may be used to enhance the birds to attack hard-to-reach pigs. Also in the levels, players can unlock bonus levels by collecting golden eggs. There are several different types of birds used in the game, distinguished by their color and shape. In the earliest levels only the basic red bird is available. As the player advances through the game additional types of birds become available. Some birds are effective against particular materials, and some have special abilities that may be activated by the player while the bird is airborne. For
Angry Birds (video game) team settled on a minimum set of requirements, even though that left nearly 30 types of Android phones unable to run the game, including some newly released phones. It was released on October 15, 2010. One month after the initial release on Android, Rovio Mobile began designing a lite version of the game for these other devices. In early 2010, Rovio began developing a version of "Angry Birds" for Facebook. The project became one of the company's largest, with development taking over a year. The company understood the challenges of transplanting a game concept between social platforms and mobile/gaming systems.