Zombie Defense

In a world filled with zombies, one thing is important and that is survival.  You need to be with other survivors to have a higher chance of surviving.  That is what the humans do, but the zombies have located their hideout and is now being invaded.   You are the last defender of the town.   This game is played via mouse and you need to defend your town from the undead.  Keep on firing till there are no zombies.  You need to be quick or you will die.  There are no power-ups in the game. Just hold them off till you can.