If you have ever played Left 4 Dead there are zombies and humans. So, that is what this is. There are witches and tanks, but humans have robots and airstrikes.
Zombies
Hunter: Can jump far distances and pin you.
Smoker: Long tongues, can choke you
Boomer: Barfs on you. All other zombies charge at you if there is barf
All zombies can also run up and punch you. They can also pick up guns and actual user zombies have tons more life.
Humans just get guns.
If you get enough skill points you can get a robot or airstrike, or witch or tank. You can even control them!
Zombies
Witch: DONT SHINE THE LIGHT OR MAKE NOISES. The Witch can kill you very easily. Only hurts humans.
Tank: A Tank is a huge zombie that can throw stuff at you. Only hurts humans
Ghost: Invisible, and can kill people x3 faster than a hunter. Only hurts humans
Humans
Robot: Very Very high armor and loaded with guns. Very slow though. Can only hurt zombies
Air Strike: Air Strike will drop a bunch of missiles and blow up everything. Can only hurt zombies
Helicopter: Helicopters stay above and shoot at zombies. Can shoot missiles every once in a while.