#A simple Pólya urn model
Here is a simple Pólya urn model : a random draw with reinforcement.
I had this idea while listening to an interview of Mickaël Launay (french) who made his thesis on the subject of reinforced randomness.
At start time the urn (which is represented by an array) contains a certain amount of each element (here color name).
On each turn, one element is drawn from the urn, and this element plus one of same nature is put back into the urn.
At each turn, elements of same nature are summed up and represented in a graph.
You can initialize the urn with some more color names.