Huangdi (reigned circa 2697-2598 b.c.e.) is regarded as the initiator of Chinese civilization. The color yellow represented earth energy in the Chinese five element system. He is attributed with many inventions, including everything from carts and boats to varioius math calculations and a game of football. Huangdi figures prominently in the medical and sexological teachings of Taoism. A book attributed to him and known as The Yellow Emperor's Classic of Internal Medicine is one of the basic texts of traditional Chinese medical practice, including acupuncture. The "Handbooks of Sex," some of the oldest books on love, were supposedly written by him nearly five thousand years ago. Upon his death he is said to have ascended to heaven because he "perfected himself through practicing the Sexual Secrets."