Introduction to the Mystery of Huashan: Under the "Sea of ​​Clouds" stone carving in Longkou, there are four circles. Among them, the two vertical ones on the left have only circumferences but no centers; but the two on the right have both circumferences and centers. The first word puzzle in Huashan is "the first difficult problem in Huashan". The "Chong Er" stone carving is located on the west peak, which means the wind and moon are boundless.