Angry Birds

Angry Birds is a puzzle video game developed by Finnish computer game developer Rovio Mobile. Inspired primarily by a sketch of stylized wingless birds, the game was first released for Apple's iOS in December 2009.^[2] Since that time, over 12 million copies of the game have been purchased from Apple's App Store,^[3] which has prompted the company to design versions for other touchscreen-based smartphones, such as those using the Android operating system, among others.
In the game, players use a slingshot to launch birds at pigs stationed on or within various structures, with the intent of destroying all the pigs on the playfield. As players advance through the game, new birds appear, some with special abilities that can be activated by the player. Rovio Mobile has supported Angry Birds with numerous free updates that add additional game content, and the company has even released stand-alone holiday and promotional versions of the game.

Angry Birds has been praised for its successful combination of addictive gameplay, comical style, and low price. Its popularity led to versions of Angry Birds being created for personal computers and gaming consoles, a market for merchandise featuring its characters and even long-term plans for a feature film or television series. With a combined 500 million downloads across all platforms and including both regular and special editions,^[4] the game has been called "one of the most mainstream games out right now",^[5] "one of the great runaway hits of 2010",^[6] and "the largest mobile app success the world has seen so far".^[7]
In Angry Birds, players control a flock of multi-colored birds that are attempting to retrieve eggs that have been taken by a group of hungry green pigs.^[8] On each level, the pigs are sheltered by structures made of various materials such as wood, ice^[9] and stone, and the objective of the game is to eliminate all the pigs in the level. Using a slingshot, players launch the birds with the intent of either hitting the pigs directly or damaging the structures, causing them to collapse and eliminate the pigs.^[10] In various stages of the game, additional objects such as explosive crates and rocks are found in the structures, and may be used in conjunction with the birds to destroy hard-to-reach pigs.

There are several different types of birds used in the game. In the earliest levels, the basic red bird is the only one available.^[8] As the player advances through the game, additional types of birds become available with specific birds being effective against particular materials. Some birds have special abilities that may be activated by the player after the bird has been launched.^[10] For example, a blue bird can separate into three small birds,^[8] a black bird explodes,^[10] and a white bird can drop explosive eggs.^[8] The pigs themselves also appear in different sizes. While small pigs are relatively weak and are easily destroyed either by direct hits or by debris from the damaged structures, larger pigs are able to sustain more damage. In addition, some pigs wear helmets as armor, making them even more resistant to damage, while pigs with crowns can take the most damage.
Each level starts with the number, types, and order of birds pre-determined.^[8][10] If all of the pigs are defeated by the time the last bird is used, the level is completed and the next level is unlocked.^[8] Points are scored for each pig defeated as well as for damage to, or destruction of, structures, and bonus points are awarded for any unused birds. Upon completing each level, players receive one, two, or three stars, depending on the score received. Players may re-attempt unlocked levels as many times as they wish in order to complete them successfully or to earn additional points or stars.