Contribute correction: Challenger Reversi

 _    _     _____    _____     __   __  
| || | ||  |  ___|| |  __ \\   \ \\/ // 
| || | ||  | ||__   | |  \ ||   \ ` //  
| \\_/ ||  | ||__   | |__/ ||    | ||   
 \____//   |_____|| |_____//     |_||   
  `---`    `-----`   -----`      `-`'