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) history of the Apple App Store, "Angry Birds" holds the record for most days at the top of the Paid Apps chart, having spent a total of 275 days at the No.1 position; "Angry Birds Rio" has been No.1 for a total of 23 days, ranking ninth on the list. In Apple's "iTunes Rewind" list of the most popular iTunes Store media for 2011, "Angry Birds" was the top-selling paid iPhone/iPod app on the App Store and its free version was the fourth-most downloaded. The game's two special-edition versions, "Angry Birds Seasons" and "Angry Birds Rio", were also ranked in