This masterpiece is by Ukrainian composer Vladislav Tarasiuk.

Very often in Christmas Tree puzzles the solution depends on the fact that whilst the pieces are symmetric relative to each other, they are off-centre on the board.  A file is therefore not available on one side that is available on the other and this gives rise to a unique solution.

What is so unusual about this puzzle is that after White’s first move, Black has two reasonable defensive moves, one on each side of the board.  White has to adopt a different winning method in each of those cases.  If either of the methods is applied to the wrong side then it fails, with Black utilising the extra file in a different way in the two cases.

It’s not easy but is a very elegant puzzle!