translation.en: Take a beer mat and rotate it by a quarter of a turn, then flip it. And then do it in the other order, and the picture will be facing in the opposite direction.
translation.zh: 拿一个啤酒垫，把它旋转四分之一圈， 然后翻转它。然后再按其它顺序做， 酒垫上的图将是朝反方向面对你的。