Pig Destruction
The primary objective of Angry Birds is to use a slingshot to propel birds into the air towards green pigs. When your bird hits a pig directly, or causes a structure to fall down on top of a pig and squash it, the pig explodes and is removed from the game. Most pigs stay in the same position throughout the game, but pigs are often protected by wooden or metal buildings so they are more difficult to get rid of. You cannot pass a level of Angry Birds to unlock the next one until you destroy all of the pigs it contains at least once.
Points
Each pig that you kill in Angry Birds earns you 5,000 points. If you manage to get though the game without using all of the birds available to you for that level, you are awarded 10,000 bonus points. Other fixtures in each level, such as the wood and metal pieces that form buildings, offer a smaller number of points--often 500. Each time you play a level of Angry Birds, the game shows you your current high score for that level. Try to beat your current high score with an even higher one.
Stars
The higher your score in a level of Angry Birds, the more stars you will earn. Each level has a maximum possibility of three stars. When you pass a level by destroying all of the pigs, you are guaranteed at least one star. Each level has a pre-determined score requirement for earning two or three stars, but the requirement is a secret. After you complete each level successfully, the game tells you how many stars you earned. Angry Birds will display a message congratulating you once you complete all levels with the full three stars.
Golden Eggs
Some levels of Angry Birds have golden eggs. Often, the eggs are placed very high on the screen and cannot be seen in the zoomed-in view of the game. Once you zoom out to see the larger version of the game, look for golden eggs near the perimeter of the screen. When you hit a golden egg, you unlock an additional level of Angry Birds. Scroll to the last page of your Angry Birds game and tap on the golden eggs to play the additional levels.