Secondly, the overall feeling of this book is ok, which is more serious than most books about compasses. I've read a lot of books, most of which have moved the contents of the compass intact, and I dare to publish them without knowing it myself. And this book, with many detailed explanations, can at least be understood by some basic people, which is very rare. Just cut a paragraph for reference, the author made a simple explanation of the destruction and death of water.