In this zombie game, you're controlling the zombies. Humans have intruded upon your graveyard, and have even thrown a party in it. You are the leader, the master, the zombie every other follows. It is up to you to drive them away by killing them and then converting them into zombies to join your army. Scientists with weapons to turn you back into a human will try to stop you. Humans killed can be turned into money. Buy upgrades with money to prolong your killing experience. Like any other game, it gets harder as the game goes on.
Wherever you move your MOUSE, your character, aka the zombie leader, will follow. Your army (if you have one) will follow the leader. Basically, all you need to do is move your mouse. The fighting will be done by the game itself.