You can jump into tons of different vehicles and use them to get from one side of the city to the other, running over zombies in the process. In fact, this is the easiest way to kill your enemies.
Different types of weapons are also scattered throughout the city, including pistols, machine guns, and grenades, all of which you can use to eliminate zombies on foot. Of course, you'll need to be very careful, because there are many, many zombies out there waiting to get a piece of you.
Your adventure also requires you to try to rescue the few survivors that are left in the city. Just approach them, and they will be saved.
Extinction 3D is a fun action game that has the pull of old GTA games mixed with that trend that refuses to die: zombies.