Golden Egg Level 13

Golden Egg Level 13 is the tenth Golden Egg Level in the original Angry Birds that is unlocked by collecting a hidden Golden Egg in Theme 8-15. It takes place in the sky, much like all levels in the eighth world, and features the pigs placed into a large sack held together by multiple Stone Blocks, a single Wood Block, and five Balloons. The sack is hanged over a row of TNT crates, and on the sides, are metal balls and more TNT crates also suspended by balloons.

Strategy
To beat the level, the player must simply send the sack containing the pigs into the row of TNT crates (or to the ground if the TNT crates are absent when the sack falls). which will kill the pigs in contact. To do this, the player must do one of two things: use a Red Bird to pop the five balloons holding together the sack, or destroy the Wood block underneath the balloons. Either method will send the Pigs to their doom.

Alternately, the player can just wait for the pigs to die inside the sack. This can happen because as the sack rocks, the four King Pigs inside slowly take damage. While this method is much slower, it is easier and can be more rewarding than the faster method, as a Armor Pig is likely to escape the empty sack and land on the row of TNT crates, netting around 80,000 points combined with the score the pigs give upon their defeat. The four Red birds in reserve will contribute 40,000 more points, for a grand total of 120,000 points.

Trivia

 * This is the only level in Angry Birds that can be completed without the use of a single Bird.
 * It is also the only level to contain multiple King Pigs.