This is very cool! All in all it looks like you *can* play offline games now, providing that both players know chess rules. Just like it happens with a physical board.

En-passant, castling and pawn promotion seem to be solid enough to play. All chess moves are now covered. Still some glitches on legal moves but nothing that you opponent couldn't remind you not to do. While the glitches get fixed....

... now all the attention turns to the UI!