At first glance, the image appears to be a spiral. But if you use your finger or mouse to trace the line, you'll find that the picture is actually composed of concentric circles.
How it works: The background of patterned diamonds is designed in such a way as to draw your eyes to the center of the image. Also, the circles are drawn in such a way that they appear to be made up of two shades of something twisted together, which helps lead your eyes towards the center of the image.
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