Serpent()

         Play the Snake with 100% Clipper code

    Syntax:

         Serpent( cColor, cColorHead, cColorMark ) -> Nil

         cColor     : The screen's color and the Snake's body
         cColorHead : The Snake's head color when it's pressed down
         cColorMark : The color of the screen's brand

    Description:

         Enjoy serpent game.

    Return:

         Nothing.

    Example:

         Serpent ( "W+/B*", "R+/B*", "G+/B*" )