Animated GIF captcha

This is an animated GIF being used as a captcha. No idea if this is a good or bad idea, but I thought it might be nice to make something a little different to the usual captchas you see.
Instead of trying to make it hard to read by obscuring the text it relies mostly on human eyes having persistence of vision and being able to read it clearly along with some simple obscuring.

Thanks go to László Zsidi who saved me some time by writing an animated gif class.

captcha

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