This is one to make your eyes hurt. Or your head.
My office is situated in an industrial estate, and in one of the other units there is a tank of some form. Maybe it holds LPG, maybe it holds water. I don’t know. But I do know that the fence is beside a fence, and that fence faces south. So on those few occasions when the sun shines, that fence casts a shadow on the tank.
The tank is circular. The fence is vertical. The shadows are ever so slightly mind-numbing!