Enter an infected zone called "Romero E5". Don't let zombies spread over the city's borders by assigning soldiers to repair barricades and shooting at incoming infectees.
Build towers and defend your base against the waves of blood-thirsty incoming zombies. Earn points to upgrade your existing towers or add more new towers.
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..