World of Wator

World of Wator is a screensaver which simulates a predator-prey model on the hypothetical planet of WaTor (Water Torus) whose surface is entirely covered with water, occupied by two species: fish and sharks. The fish exist on a never ending supply of plankton. Both sharks and fish live according to a strict set of rules.

This simulation of a simple ecology is highly dynamic as both species are walking a thin line between continuing life and extinction. In every time step, a fish moves randomly to one of the four neighboring fields, provided it is empty. Every fish has a predefined "breed time". On exceeding this time, it gives birth to a new fish in one of the neighboring cells, provided this randomly selected cell is free. (If not nothing happens.) Breed time counter of both the original and the descendant fish will be reset. Sharks move randomly to fields that are either free or occupied by fish.

Every round they lose one point of energy. If they enter a field occupied by a fish they eat the fish and gain a defined amount of energy. If the energy level drops below zero the shark dies. If the energy exceeds a predefined value sharks create an offspring in a free neighboring field. The energy is split evenly between the parent and the child