In Angry Birds, the player controls a flock of multi-colored birds that are attempting to retrieve their eggs, which have been stolen by a group of hungry green pigs. In each stage of the gameplay, enemy pigs are sheltered by structures made of various materials such as wood, glass, and stone resembling children's toy building blocks. The objective of the game is to eliminate all the pigs on the level. Using a slingshot, players launch a limited set of birds with the goal of either striking the enemy pigs directly or damaging their surrounding structures, causing the blocks to collapse and pop the pigs. The player must set the angle and force of the bird's travel by pulling back on the slingshot (using intuitive touch-controls in the mobile versions). The launch process is quick and casual, with no visible trajectory data, and a player simply selects a point in the X-Y field behind the launch post from which the virtual slingshot will be released. In various stages of the game, additional objects such as TNT 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 hidden in the levels, players can unlock bonus levels by collecting golden eggs.