Creature#exists

Controls if this Game Object is processed by the core game loop.
If this Game Object has a physics body it also controls if its physics body is updated or not.
When exists is set to false it will remove its physics body from the physics world if it has one.
It also toggles the visible property to false as well.

Setting exists to true will add its physics body back in to the physics world, if it has one.
It will also set the visible property to true.