-Styles must be improved (full width for smartphones, selectable text for PGN...)
-Tooltip text should fade (even when mouse stay on it, especially for small screens)
-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)
+Translations (including About page), refresh rules