-End of game a bit too verbose: should just say "Black win" ... + show PGN
-Styles must be improved (full width for smartphones, selectable text for PGN...)
+PGN text is not selectable (understand why?!)
+Checkered stage 2: switch button at reserve position (or on top).
+Mode expert: game.js, button on top (with online indicator)
+Turn indicator on top too (black or white)