I have a suggestion that is to add in ability for the zombies and is activated using right click with a cooldown of 50 seconds. For fast zombie class they go 2x faster for 10 seconds. Half zombies can go invisible for 8 seconds (take no damage after ability runs out for 10 seconds). Headcrab zombies can have health regeneration for the zombies around it with the heal of 120 health. Zombie can jump super high for 15 seconds. I hope my suggestions are good. Peace~!