When the demo is started, a window is created and some things are drawn in it. A menu of options is presented; select an option and then click the mouse one or more times inside the graphics window.
The code is fairly simple.
You must have the Java virtual machine installed to run this demo; you can get it for Windows (msjavx86.exe) here.
The best things in life are free: this demo uses the free software Gnu Common Lisp (GCL), XGCL, X windows [see also XFree86], Java, and WeirdX, a Java implementation of an X server.