The air started stinking when the zombies appeared. Not only are they are grossed, they are also chain smokers and this causes the air to be polluted. Also, they would eat anyone that is close to them. The kids need to be protected and there are only two of you left to defend the kids. The game is played with a mouse and the idea here is to get the zombies before they can even get closer. Each kill would earn you money and you can use that to buy better guns or upgrade your existing ones. The game gets more difficult as you make some progress.