You must traverse the desert, kill lots of zombies, and to get to your escape helicopter in Earn to Die. Buy a vehicle and drive it as far as you can each turn to earn money for upgrades. You also earn money by killing zombies in creative ways and doing stunts.
Your speed and fuel are indicated at the bottom left of the screen, how many feet left to reach the helicopter is indicated on the right. At the end of each day your distance in feet and amount of money earned will be displayed. Head to the garage for upgrades to your vehicle, or buy a whole new vehicle. Each mechanical item or weapon has individual upgrades once purchased.