Become a super kangaroo, even though it's not gonna be easy. You have to take care of all the babies, and every day you'll get more and more things to do. You gotta be able to control all the babies.
Aim well and fire until you destroy annoying Bieber. As you move on you'll find some unlucky obstacles on your way. Avoid them or make your ammunition bounce to reach your victum. Use your mouse.