The shadow is the thing on the floor, below her. It breaks the CW, CCW degeneracy.?? what's impossible about the counter-clockwise spin? her posture seems a little awkward CCW, but as an object I don't see the impossibility (it doesn't have to be a shadow, maybe it's a very opaque black object, or a high-contrast picture with the light source behind the object). both CW and CCW spins work equally well for me.