Astronomical chess or Astrological chess for seven is a game from the book "Libro de los juegos" (Book of games), written under king Alfonso X the Wise in 1283. The game was played on a round board with concentric circles. The sky, zodiac signs and planets are the elements of this chess. The book described the games and problems of playing situations in chess, dice and other board games that formed the basis of modern backgammon.