This is not a spiral

Slightly off-topic, here, but I see lots of these optical illusion posts on the web, and although some of them are pretty impressive, this one borders on voodoo. I had to run my mouse pointer over the blue traces a few times to persuade myself. I’ve overlaid some big yellow circles on the original image, which you can see, below, after the jump, to save you the trouble. [via Neatorama]