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) Android in some nations. An update called "Bad Piggy Bank" enabled players to buy out the in-game ads. In October 2010, Microsoft suggested on one of its websites that a Windows Phone version of "Angry Birds" was in development. Rovio complained that Microsoft had not asked permission to make such a statement, noting that at that time it had not committed to design a Windows Phone version. Although Rovio asked Microsoft to revise its site to remove references to the game, a Windows Phone version was ultimately released in June 2011. Near the end of 2010, Rovio stated that it