This simulation pits a group of sheep against a lone wolf. If a wolf catches a sheep, it usually turns it into another wolf. However, there's a slight chance it will turn the sheep into a zombie. Zombies pursue wolves and turn them into sheep. Sheep pursue zombies and turn them into sheep.
The system is like the Sheep vs Wolves + Zombies. However, it introduces enough negative feedback to balance the positive feedback and create an equilibrium.