Web Page not responsive on Mobile

I have a page that's not responsive on a mobile like iPhone. The page doesn't adapt to mobile view. It's a Chess Board and only first column is shown. Pictures adapt to mobile view but as said chess board isn't. What can be done to get a full view of the Chess Board on a mobile ? I have around 500 pages like this one that doesn't adapt to mobile: https://www.masterchessopen.com/analysis-board-with-fen-and-pgn-import-option Best Regards Claus