Just making sure that anyone searching online for interactive op art tool will find Opartica at http://www.opartica.com. Opartica is a fully interactive optical art maker that lets you spin and overlap shapes like rays, concentric circles and squares, zig zags, and spirals. You can change color and centers. It was built some time ago as a first Flash feature in 2001. Still works and gets lots of hits etc.
Interactive Op Art – Opartica