If the dancer stops pirouetting, you may have looping turned off in your browser preferences. Either turn it back on or just keep reloading the page (Alt R or Command R or see the browser button to do this towards the top of the window, sometimes it is an icon with revolving arrows...)
This figure can appear to be turning clockwise or anti-clockwise (as judged from the left of the picture). Some people think that when the figure is seen upright, this 'one way/another way of seeing it' demonstrates the preponderance of different viewers "left brain" or "right brain". But in the above, there is no top and lower brain to explain the preponderance of a tendency to see it one way rather than another.
If you look very closely at the way the figure is constructed, you might be able to see just why it can be seen both ways. Take the tip of the toe, for instance. It is is a point that moves up and down (in the upright figure it would be across). Every other point is like this. There are no clues whatsoever as to which way in 3 d it is going. All is done by the brain. It is not clear it has to do with left and right brain preponderances.