Zombieville USA has two simple objectives: shoot zombies and stay alive. Your weapons and ammo are in short supply, so using them at the appropriate time is critical. As you progress through the levels, you can jump into houses that will supply you with cash and ammo, as well as keep you protected from the zombies. At the end of each level, you can use the cash to upgrade your weapons and replenish your health. Source: Wikia Website.