http://www.michaelbach.de/ot/ I just spent the last 45 minutes looking at some of the demonstrations on that site. Apart from sore eyes and a minor headache, I find it fascinating. Most of the demonstrations allow you to manipulate sliders to adjust different aspects of the illusion. Some of them seemed bogus: telling me things were or weren't moving when I swore otherwise. I wouldn't know how to go about proving any shenanigans, though. Anyway, does anyone else like optical illusions? If so, what are some of your favorites?