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) were released, Angry Birds became "Free App of the Week" on the Apple App Store until March 14, 2013, and became an instant hit on the Top Free App charts on the App Store until March 18, 2013, when the app returned to the normal price of $0.99. On June 17, 2013, Rovio teased on its Facebook page that Red, the main protagonist of the game, would receive an ability in a new episode. On June 26, 2013, Rovio released a YouTube video, uncovering three new facts: the episode would be called Red's Mighty Feathers, the update would come in