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 "Bad Piggies: Egg Recipes", along with doodle books based on some characters of the game. After a few weeks of the release of Angry Birds Space, they also released Angry Birds Space books about numbers, alphabets, and stickers. On 20 March 2012, "National Geographic" published a paperback book titled "Angry Birds Space: A Furious Flight Into The Final Frontier" shortly before the release of "Angry Birds Space" which became available on 22 March 2012. National Geographic also has a book titled "Angry Birds Feathered Fun" for learning all about birds. In the same year, Rovio created a contest with the