I made a quick & dirty agent simulation with Construct. Here's a screenshot : <img src="http://dl.dropbox.com/u/1412774/AgentSim/demo.png" border="0">
Each agent has some energy at the beginning, and search for some food. If it eats some, he get back some energy. If energy goes down to zero, it dies. They can't see food if it's too far away from them...
http://dl.dropbox.com/u/1412774/AgentSim/index.html
The "graph" shows how much agent you have with energy under 20, with energy between 20 and 40, and so on...
Edit : here's a link to the .capx : http://dl.dropbox.com/u/1412774/AgentSim/agentsim.capx
There's several Layout, each one present a new "complexity" in the simulation, but only one layout at a time is running, you need to set it at the properties of the IDE (and there's no possibility to change layouts during the simulation).