Read this then follow the link: When one stares at the cross in the center of the image for 10?20 seconds, two effects will appear in order: One, the moving empty space between dots will appear as a green dot. Two, the moving green dot will appear to wipe out the purple dots, until only the green dot is visible. A separate effect appears if the eyes move away from the center, showing a ring of green dots. lilac chaser
