Hiding the first clues, a version of Shan Hai Jing (Classic of Mountains and Seas) published in 1180 during the Song Dynasty (960-1279) is the book's earliest edition found to date. Players need to have a specific understanding of the distance between mountains, and then find the answer to the first puzzle using a specially designed "ruler". The "ruler" is made of paper with the mountains' information printed on it. Players will find the answer once it's folded.
