A strange attractor is a chaotic system from which patterns emerge. Hopalong is one of a collection of formulae that, when plotted, produce unusual and strikingly beautiful images.
The Go button starts the plotter.
The Random button generates new values for P, Q and R.
New values entered in the P, Q and R fields do not take effect immediately. You'll have to click on Go again to restart the plotter.
The Hopalong Fractal was originally by Barry Martin of Aston University and published in Dewney's article in the Sept 1986 Scientific American.