Contribute correction: Challenger Reversi

 __   __    ______   _____     _    _   
 \ \\/ //  /_   _// |  __ \\  | || | || 
  \   //    -| ||-  | |  \ || | || | || 
  / . \\    _| ||_  | |__/ || | \\_/ || 
 /_//\_\\  /_____// |_____//   \____//  
 `-`  --`  `-----`   -----`     `---`