Theme 1-5 (A.K.A Stack Castle) is the fifth level of Angry Birds, and the first to have Large Pigs. The player is supplied with 4 Red Birds. There are also three Small Pigs and two large pigs below them.
Hit the first Red Bird near the top of the highest horizontal wood block. The block should move aside due to the weight of the stone boulder, and the boulder should crash through the three small pigs. The rest of the structure should destroy one of the lower horizontal wood blocks, allowing the boulder to crush the two large pigs.
In the Google Chrome version and the new version, the two large horizontal wood blocks near the base of the structure are replaced by glass.