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Many thanks goes to @Retudin in a comment on my last question for this idea.


In a chess position, pieces can be restricted as to how many moves they can legally make in theory. Since my previous question covered n=1, it is time for n=2!

Given that:

Every single piece, up to 32 in total, may be used.

Construct:

A position in which as many of them as possible have exactly two legal moves.

In the likely advent of a tie, the position containing the shortest proof game wins.

Good luck!

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Partly based on @Vepir's 19-move answer (Most similarity is due to convergence but I admit I borrowed the Bf1.)

but 2 1/2 moves faster for 16 moves exactly:

Proof game:

[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"] 1.b4 d6 2.Nc3 Bh3 3.g4 h5 4.Bg2 a5 5.Na4 e5 6.Bd5 Be7 7.Bb3 Bg5 8.c4 Bh6 9.Bb2 Bf1 10.Bc3 Nf6 11.f4 Kf8 12.Rb1 Nc6 13.Nb2 Qb8 14.Nf3 Ne8 15.Nh4 Nd8 16.Ng2 d5 *

Final position:

enter image description here

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  • $\begingroup$ Beaten by half a move! Nice work. It seems less symmetry allows more optimization. $\endgroup$ – Vepir May 14 at 10:48
  • $\begingroup$ @Vepir The problem is not symmetric (Q!=K). Also, my gut feeling is that this is still not optimal. No idea why this kind of puzzle is so addictive... $\endgroup$ – loopy walt May 14 at 10:52
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New answer

I found a new solution that is 2 moves better than my previous one!

Big thanks to the answer by Retudin for the new pawn structure idea!

Pieces:

All 32 pieces have exactly 2 legal moves.

Moves:

(16 for each side, then one more for white.)

1. a4 h5 2. c4 f5 3. Nh3 Nc6 4. g4 Ne5 5. Rg1 Nf7 6. Rg3 b5 7. Rb3 Rb8 8. d4 e5 9. Ng1 Rb6 10. Na3 Rg6 11. Nc2 Ba3 12. Bh6 Rg5 13. Rb4 Nf6 14. Qb1 Kf8 15. Qa2 Kg8 16. Rb1 Ne8 17. Qa1

Position:

enter image description here


Old answer

Pieces:

All 32 pieces have exactly 2 legal moves.

Moves:

(18 for each side, then one more for white.)

1. Nc3 b5 2. Nf3 g5 3. h4 Bg7 4. a4 Bd4 5. Rh2 Bb6 6. d4 Bb7 7. Bf4 Be4 8. Be5 Bg6 9. Bg7 Nh6 10. e4 Nf5 11. Bc4 Nd6 12. Bd5 Na6 13. Bb7 Nc5 14. Kf1 Ne6 15. Bf8 Ng7 16. Bc8 Nb7 17. Qb1 f5 18. Nd1 c5 19. Ne1

Position:

enter image description here

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Pieces

All 32 pieces have 2 moves

Correction (thanks to Rewan's remark): The king has a 3rd move (castling)

Moves

1 h4 a5 2 Rh3 Ra6 3 b4 g5 4 Bb2 Bg7 5 Be5 Bf6 6 Bh2 Bd4 7 Nc3 Ba7 8 Rg3 Rb6 9 f4 c5 10 Ne4 Nf6 11 Nf2 Nd5 12 e4 Nc6 13 Ba6 Nc7 14 Nf3 d5 15 Ke2 Bh3 16 Rg4 Rb5 17 Qh1 Qa8 18 Ne1 Nd8 19 Kd1

Position:

enter image description here

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  • $\begingroup$ @Vepir Now you are both tied! $\endgroup$ – Rewan Demontay May 13 at 19:48
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    $\begingroup$ Wait, I just noticed a flaw here! The Black king actually has 3 possible moves due to the possibility of castling! $\endgroup$ – Rewan Demontay May 13 at 19:54
  • $\begingroup$ Oeps.. Does that also count as 3 for the rook? $\endgroup$ – Retudin May 13 at 19:57
  • $\begingroup$ No, castling is specifically a king move as defined by FIDE's laws. The rook only has two moves. $\endgroup$ – Rewan Demontay May 13 at 19:58
  • $\begingroup$ So just move the king to invalidate castling? $\endgroup$ – justhalf May 14 at 2:33

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