"Things You Wouldn't Know If We Didn't Blog Intermittently."
23 March 2011
When you watch the video, you may need to freeze-frame it to inspect the checkerboard pattern. The little dots create the illusion that the board lines are not rectilinear; when they are blown away by the guy wearing the hat (upper left), the pattern becomes evident.
The creator of this video has a much longer video incorporating a variety of optical illusions at this YouTube link.