Predray
This is at heart a predator prey simulation, but during development evolved into something more of a sandbox world. It contains various interactive simulations of wind, water, rain, grass, fire, trees, numerous particles and flocking AI.
It is also capable of running genetic algorithms to determine the best animal genes to stabilise the zebra and lion populations for a given environment. This includes variables such as birth rate, hunger rate, thirst rate and more.
This is a basic video showing Predray in action. I'll upload a higher quality one soon as this is quite old and low res.
Downloadable Application
Controls
M - Options menu
Escape - Main menu
Left Click - Use current tool
Middle Click - Draw Zebras
Right Click - Change tool
Mouse Wheel - Change Tool
Hold Right click and drag - Change brush size