So here are the rules:
#1 You start with two chessboards: one is just a normal chessboard and one is empty.
#2 If you move any piece (except pawns) into the center on the normal chess board, then it moves to the corresponding central square on the empty board (Board 2).
#3 When any of your pieces are on Board 2, then the only way to get back on Board 1 is to go to any of the edges. If you do this, then the piece will appear on Board 1 on the corresponding edge square.
This creates some interesting tactics. For example, this is mate in two: Queen E4+ (I am threatening to play Queen e8 on Board 2 and to take the King). So, Kf8 is the only move, then Queen e7 on Board 2 Checkmate (because I am threatening to play Queen f8 on Board 2 to move to Board 1 and you cannot stop it!)
And, you may think white has a plus, but if you look deeper, it's not so simple. Take a look at this next position:
He took your rook.
And it's not so clear who is better: white's queen is silly; however, black is down a rook.
I hope you enjoyed this blog post! Julian.