-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)
-incheck by checkered pawns: not marked (because of turn changed?)
+Finish rules translation in Spanish
+Design: final touch (gain extra space on top, using space on the right)
+Crazyhouse: center reserves, grey if zero available, numbers superimposed