No.897 by Kjell Widlert & Thomas Maeder – A new interesting interpretation of the previously published problem by Kjell Widlert, Sp.Prize, 1st Riga Black Balsam TT-2015. Authors comment: “Compared to the Riga Balsam problem, we now have one extra change of phase – which must be chosen very carefully – in each solution.”  (JV)

Definition:

Half-neutral piece: Piece which can exist in black, white or neutral state and changes its state by the rules:

• A piece in the neutral state may be moved by Black or White, and after move it changes into black or white state respectively.
• A piece in the white state may be moved only by White, and after move it changes into its neutral state.
• A piece in the black state may be moved only by Black, and after move it changes into its neutral state.
• Only a half-neutral pawn can promote into half-neutral figure.

Additional features of half-neutral pieces:

• Castling with half-neutral King is possible with hK in white phase on e1 (White castling) and hK in black phase on e8 (Black castling). After castling the hK becomes half-neutral phase and can become mate.
• A play is possible also with only one half-neutral King on the board (in white, black or neutral phase).
• By the notation: “h”=half-neutral piece, states are marked with “w”(white), “b”(black) and “n”(neutral).