City defense has begun! Alien Zombies are coming, and they're angry! Let's form a defense line now! Protect the bustling metropolis from invasion! End this alien conquest and build one mass control and city defense base, police officers, call all the soldiers for help, quickly clone the soldiers, and let's be the police, push them all! You will visit a post-apocalyptic world in Zombie Idle Defense where most of the people have evolved into alien zombies. Help police officers who must defend themselves against endless waves of enemies.