The Spinning Silhouette - The dancer is a 2d shadow so there are no tricks: it's not changing direction. It depends on how your brain is seeing it... you could be able to see it clockwise, anti-clockwise or both. You can also see it as a test. Here are the results: http://www.news.com.au/heraldsun/story/0,21985,22556281-661,00.html