The states of each creature include energy level, which direction they are facing and physical location. About one hundred creatures are placed in the arena to start off with enough food to keep them more than happy. The bugs lose energy all the time. Different actions lead to different amount of energy loss. To keep going a bug has to keep eating his greens.
Any energy spent in the arena is reconstituted as more greens randomly.
The usual history of a Neorotic system is first those creatures who have no clue quickly die out. Those unable to move quietly expire whilst those who can move but have not worked out how to eat are next. As the creatures get older so their energy demands grow till it becomes next to impossible to eat enough to move. This is where reproduction comes in. One of the banks of commands open to a creature is to reproduce.