Kill all zombies before they reach the top of the canyon and wreak havoc on the citizens of Zombville. Kill them all, make money, upgrade your weapon and buy power-ups. Good luck!
It's a nightmare. You are trapped in an abandoned mine with an injured comrade at your side against God-knows-what. Make your stand, get out alive. Three words of advice: shoot to kill. These things are not human, they are monsters..