Angry Birds

Angry Birds is a puzzle video game developed by Finland-based Rovio Mobile, in which 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. Inspired by a simple sketch of stylized wingless birds, the game was first released for Apple's iOS in December 2009. Since that time, over 12 million copies of the game have been purchased from Apple's App Store, which has prompted the company to design versions for other touchscreen-based smartphones, including those using the Android, Maemo, webOS, and the Symbian^3 operating systems. Rovio Mobile has supported Angry Birds with numerous free updates that add additional game content, and the company has even released stand-alone holiday versions of the game.

In Angry Birds, players take control of a flock of birds that are attempting to retrieve eggs that have been stolen by a group of evil green pigs. On each level, the pigs are sheltered by structures made of various materials such as wood, ice and stone, and the object 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, which would cause them to collapse and kill the pigs. In various stages of the game, additional objects such as explosive crates and rocks are found in the levels, 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. As the player advances through the game, additional types of birds become available; some of these birds are more effective against particular materials or they have special abilities that are activated by tapping the touchscreen while the bird is airborne. For example, a blue bird will separate into three smaller birds, a black bird will explode and a white bird will drop explosive eggs. 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. Also, some pigs wear helmets as armor, making them more resistant to damage.

Each level starts with the number, types, and order of birds pre-determined. 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. 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 levels as many times as they wish, and may also replay completed levels in an attempt to improve their score.

Release
The initial iOS version of the game included a single episode entitled "Poached Eggs," which contained three themed groups of levels, each with 21 levels. From time to time, Rovio has released free upgrades that include additional content, such as new levels, new in-game objects and even new birds. As updates have been released, they have been incorporated into the game's full version offered for download from each platform's application store.

The first update, released in February 2010, added a new episode called "Mighty Hoax", containing two new themes with 21 levels each. Updates released in April 2010 added the "Golden Eggs" feature, which placed hidden golden eggs throughout the game that would unlock bonus content when found, and a new episode called "Danger Above", which initially contained a single theme of 15 levels. Two later updates added two more themes to "Danger Above", each with 15 levels. "The Big Setup" episode, containing two new themes, 15 new levels and additional Golden Egg levels, was added in June 2010. "The Big Setup" was later given two more themes of 15 levels each.

A fifth episode, called "Ham 'Em High," launched in December 2010, in celebration for the game's first year in the Apple Store. "Ham 'Em High" contains 15 levels in a single theme, and a new bird, called the Mighty Eagle, which can be used to clear any level. The Mighty Eagle may be used once per hour to clear any uncompleted levels. However, when a level is completed using only standard birds, this limitation is removed. The Mighty Eagle can then be used in previously completed levels to play a mini-game called "Total Destruction" in which the player attempts to destroy as much of the scenery as possible, both with the standard birds and the Mighty Eagle; achieving 100% destruction earns the player a Mighty Eagle feather for the level.

The Mighty Eagle is offered as a one-time, in-game purchase, and is currently available only for iOS, as its App Store customers have iTunes accounts with pre-linked credit cards. Rovio has begun testing an Android update called the "Bad Piggy Bank" with the Elisa wireless service in Finland, which allows users to charge in-app purchases, such as the Mighty Eagle, to their mobile phone bills; the service is expected to become available to other Android users in the second quarter of 2011.