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Here's a small problem for you all to breeze through tonight!

It's White to move and selfmate themselves in 7 turns.

enter image description here

Can you tell me what the special concept is that arises from this problem?

As always, have some fun!

This position took me hours to create! It was a personal hunt that I decided to put on PSE as a puzzle!

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  • 1
    $\begingroup$ FEN: 7N/8/2R2B2/1pb1n3/1P2Pp1p/B1kBQp1p/2P1pK1P/4R1Nb w - - $\endgroup$ – Arnaud Mortier Aug 10 at 14:50
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Observe

that the only Black piece that can move is the bishop, and there is nothing it can achieve. If White could remove their Bishop that's in the Queen's way on d3, it would almost force the f4 pawn to capture and deliver checkmate, except that with the Bishop gone now the Black King would be able to move. So we need to cover its escape square first.

A nice idea that doesn't work

is to have the knight travel to capture the wandering bishop and make fxQ the only possible move. It is nice to see that the knight can come as close as g3 safely (since capturing it on g3 would be checkmate which Black is trying to avoid), but then the bishop can simply avoid the h1 square and capturing it would allow uncontrollable pawn moves/promotions.

Final comment

It is a pity that there is no solution where the bishop moves to c4, forcing selfmate but this time with two possible checkmating pieces, the pawn and the newly unpinned bishop on c5. Indeed, for such a solution to exist, you would need to be able to protect the bishop on c4 and cover the escape square c2, which could be done by the knight only if the a3 square was available.

Solution:

[FEN "7N/8/2R2B2/1pb1n3/1P2Pp1p/B1kBQp1p/2P1pK1P/4R1Nb w - - 0 1"]
1. Nf7 Bg2 2. Nd6 Bf1 3. Nb7 Bg2 4. Na5 Bh1 5. Nb3 Bg2 6. Na1 Bh1 7. Bxb5+ fxe3#

apronus link

The concept that could be considered arising from this problem could be

Toroidal chess. Identifying the opposite pairs of edges of the board would allow the knight to jump to the desired square in two moves:
1. Nb7 ... 2. Na1

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  • $\begingroup$ You still need to tell that concept, pretty please! $\endgroup$ – Rewan Demontay Aug 10 at 16:50
  • $\begingroup$ @RewanDemontay I believe it's either related to the rot13(gur xavtug pbzvat nyy gur jnl sebz n pbeare gb nabgure, be gb gur ovfubc orvat hfryrffyl genccrq, ohg V pna'g chg n anzr ba vg...) $\endgroup$ – Arnaud Mortier Aug 10 at 16:56
  • $\begingroup$ It's the first option. $\endgroup$ – Rewan Demontay Aug 10 at 16:57
  • $\begingroup$ @RewanDemontay edited. $\endgroup$ – Arnaud Mortier Aug 10 at 17:05
  • $\begingroup$ Where did you get Toroidal Chess from? Your confirmed guess was good as is. $\endgroup$ – Rewan Demontay Aug 10 at 17:08

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