Instructions
Touch and hold the bird in the slingshot to the left of the screen. With your finger still touching the screen, slide your finger to the left to pull the slingshot band back. You can adjust your aim by sliding up or down on the screen. Take your finger off of the screen to release the slingshot and shoot the bird toward the pigs. The object is to aim the birds in the slingshot at either the pigs or the buildings. Hitting the buildings can knock walls or ceilings onto the pigs and kill them. You may have to practice aiming the birds to be effective, but this will not affect your ultimate score because you can always replay a level.
Use bird superpowers to increase your pig kill rate. You can activate superpowers by tapping the screen while birds are in flight, although not all birds have special powers. Blue birds can split into three separate birds. Black birds can explode. Green birds have the ability to boomerang.
Utilize special objects in the buildings like bombs and stones in higher levels to kill pigs. Do this by aiming the bird at these objects. If the bird hits the special object, it will activate and help destroy hard-to-kill pigs.