In the highest tower furthest away from the slingshot, there is a TNT crate. Though most of that tower is made of metal, the rectangular block right in front of the TNT crate is wood. The player should shoot the Yellow Bird high into the air, and directly at that block so that it smashes it. It is a difficult shot to make, but after a few tries, the rectangular block would be hit and destroyed, and since it is part of the base of the tower, the whole structure will collapse. The TNT crate would be ignited, and the falling metal blocks would be pushed into the other two towers, destroying them in the process and killing all the pigs.