Defend Ground - from zombie

This game's goal is to defend ground from zombie.
Zombies come to tank on entrire screen.
You must defeat zombies.
There is a tank in the center.
If you touch anywhere on the screen, tank will fire bullet to the spot.
You must shoot zombie with this bullet.
Shoot zombies which come here and there fast.
Must defend precious ground.
Before zombies occupy the ground, you need to defend the ground by shooting zombies.
Now defending ground is started.
Defend ground! pretect ground!
Start struggling with zombies.
Compare your score with other's in global leaderboard.