As the most basic horizontal axis in the coordinate system of life, the X-axis represents the road a person has traveled in his life. It is not necessarily as straight as an axis, but it is always a "central axis". Because everyone has his own higher goal, there is a Y axis in the coordinate system of life. Although the XY axis in the coordinate system is infinitely extended, the life span is not that long. Although the goal can be unlimited, it is not enough to live a truly wonderful life. Therefore, the Z-axis representing depth appeared. .................... should not live too tired, but enrich himself. You have a certain height and a long distance, and infinite depth is the best life.