Are you ready to clear the level from the invasion of zombies? Your your M4 rifle and get all hiding zombies. Mind, that the amount of bullets is limited.
What would you do to stop the invasion of zombies? Your gun is powerful, but they all hide and wait for the right moment to attack. Don't waste your time and act now! Kill them all with a help of ricochet. Think of the best trajectory and get zombies, that were hiding from you.