created with NetLogo
view/download model file: buttons.nlogo
This is a NetLogo model of the buttons phase transition presented in Stuart Kauffman's book "At Home in the Universe".
To use: click the "setup" control to randomly scatter the initial set of buttons, followed by the "go" control to run the simulation. The "buttons" slider controls the number of buttons used, and the "move" control selects whether or not the buttons move toward the cluster. (The latter was a suggestion by Merle and Dede .. thanks!)
Initially the buttons are randomly placed on the patches. Each step ties a randomly chosen pair together. This results in isolated pairs for quite a few steps .. then threes appear, and fours. When the number of steps is about 1/2 the number of buttons, a rapid rise in the size of the largest cluster occurs. The buttons in the two sets of buttons being merged in any step move towards each other if there are empty spaces for them to occupy.
See the ComplexityWorkshop Tutorials for more information.