http://education.mit.edu/starlogo-tng/index.htm
From MIT.
This is actually a graphicsl programming environment for kids, where they can program creatures running in a 3D world. This is in fact more complex than that, as the programming environment is meant for what is knows as “complex systems”, i.e. the interaction between a large number of “actors” each having it’s own program. This can lead to “emergent behavior”.