2.1 Repetition using Circles
Look here for my Circles example and the source code. I like the gaussian random number generator that Java provides.
2.2 Variety using Triangles
Here is an example of variety using Triangles and the source code.
2.3 Rhythm using Lines
A simple example of Rhythm using Lines and the source code.
2.4 Physical Balance
This is my whizzy Balance Beam demo, but it depends on some features in JDK 1.1 -- it won't work with older viewers. If you're still interested, here's its source code