Alice Chess is a chess variant played using two chess boards rather than one. Its name is a reference to Lewis Carroll's character, Alice. Like a number of other variants, it was invented by V.R. Parton.
All pieces move in the same way as in standard chess, except that Alice Chess is normally played without the en passant rule (see rules of chess). At the start of the game, the pieces are set up in their normal position on one board, with the second board empty. When a move is played, the piece moved passes "through the looking glass" onto the other board. For example, after the opening moves 1. d4 Nf6 (see algebraic notation), the position on the two boards is as follows:
Captures are made on the board the piece begins on.
For a move to be legal, the destination square on the board it will end up on must be empty, and the move must be legal on the board on which it is played.
A short game of Alice Chess (notated in algebraic notation) might run 1. e4 d5 2. Bc4 dxe4 (on the second board) 3. Bb5 mate (the bishop moves back onto the first board). All the pieces which moved to the second board have either moved again and so returned to the first, or have been captured, so the final position in this game is as follows:
At first glance it might seem that black can interpose a piece between white's bishop and his king to block the check (playing, for example, Bd7 or Nc6), but any piece so interposed immediately disappears onto the other board. Black can also not play Kd7 to move his king onto the other board, because this move is not legal on the board on which it is played (the king on d7 on the first board is still in check). Therefore, black is checkmated.