Via Terra Byte. If you stare at the swirling silhouette figure long enough, you should see her swirling left sometimes and right sometimes, at least, we can.
The swirling silhouette is an optical illusion.
We have discovered that if you stare at the shadow of her lower foot, that shadow foot goes back and forth left and right but never goes full around, and that is the secret of the entire figure – which never does in fact go around in a full circle. We looked at the animated dancer.gif offline with Paint Shop Pro Animation and that is in fact the conclusion to be drawn.
By the way, the shadow of the arms at the bottom goes right – middle – left always.