Enigma
Stare at the center of the figure for a while. Some scintillating activity will build up in the violet and blue annuli. Some observers also report a circular rotation within these regions; things will begin to turn around in circles?
不可思议的光圈
盯着中心的圆看一会儿，你会觉得紫色和蓝色的圈在变大，还有的人可能觉得这些圆在旋转。