The things in this site are Java applets.
The applets all work pretty much the same:you load them, and they draw.
If you click on them, they quit drawing. The spacebar erases.
That's all the interaction there is.
Some of them need to be stopped (tile2, esp.); others should be run overnight.
They have variables that are randomly set; they will draw different pictures each time.
If you want to learn how to make your own,
look at the source for one of mine, by clicking on the title, under the picture.
hatch3d (2001) -- Java Applet