The pieces are moved magnetically apparently. Which means the pieces must be ferromagnetic. Now this is just speculation on my part, but if the pieces are magn

The pieces are moved magnetically apparently. Which means the pieces must be ferromagnetic. Now this is just speculation on my part, but if the pieces are magnetic, they can have a different polarization for black pieces from the white pieces. So during a human move, the computer would observe: 1. A field losing polarization when a piece is moved away 2. Another field gaining polarization when the piece is moved to it or changing polarization when a piece was captured This is enough information to reconstruct moves with multiple involved pieces. Even pawn promotion, though limited to captured pieces, can be tracked assuming the off-board fields are monitored too. One limitation here would be that the player is not allowed to slide their pieces, because the computer would not see when the piece was released and could respond too soon.