Star

In the Angry Birds series, Stars are used as a format of ranking(s) system. When the player finishes a level, he/she is awarded one to three stars, with one being for simpliy finishing the stage, two for finishing the stage while also having a good score, and three for finishing the stage while also obtaining a hard-to-obtain score for that level, or utilitising a complex tatic to finish off the pigs using fewer birds, and with more damage to the structure itself. The difficulity for obtaining a three-star ranking varies with each level.

Format
When a stage is first unlocked, there is no writen score or stars collected. As stated above, to collect stars, the player must finish the level, and based on his/her performance, he/she will be given a mininum of 1 or maxium of 3 stars for the level. If the player is able to do this for all of the levels offered in an episode, a Golden Egg is given to the player. These variants of Golden Eggs are the most difficult to obtain.

In the original Angry Birds the Three-Star Golden Eggs unlock a minigame that if it's functions are done in a specific way, he/she will receive a Golden Egg Star. Angry Birds Seasons' Three-Star Golden Egg levels are actual levels that are played like any other level in the series.

Trivia

 * Many other physics-based iOS games, such as Cut the Rope and Save Toshi use the same, or simliar three-star format. However, the former allows the player to end the level with a zero-star ranking, and the later allows players to get a three-star-plus ranking.