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2 problem(s) found in 6306 milliseconds (displaying 2 problem(s)). [COMMENTDATE>=20200919 AND NOT K='Sammlung Brian Stephenson' AND K='Chess4E71'] [download as LaTeX]

1 - P1379499
Andrew Buchanan
1135 Julias Fairies 02/10/2016
P1379499
(3+7)
h#5
Chess4E71
1. c2! b3+ 2. c3 bxc4ep+ 3. d4 cxd5ep+ 4. e5 dxe6ep+ 5. f6 exf7ep#

Not e.g. 1. c3? b4?? 2. Kg7 bxc5 3. Kh8 cxd6 4. Kg7 dxe7 5. Kh8 exf8=D# as wPb2 has lost double move rights

Not 1. c3? bxc3 2. d4 cxd4 3. e5 dxe5 4. f6 exf6 and no h#1 due to bPc5

Not 1. c3? c2 2. cxb2 c3 3. b1=L Lb2 4. La2 La1 5. Lg8 c4#? as 3 bPs can make double move to block the check
play all play one stop play next play all
Either the current position is a starting position, or White has just played 0. ... b1-b2, from a position with an impossible check which must therefore have been the starting position itself. In either case, none of the Black pawns have ever moved, and so are eligible to make a double move. wPc1 has also never moved. But what of wPb2? We are up in the air as to whether b2-b4 is legal.

Since we can never prove that a position is not a starting position, the default convention is that it is *not* the starting position. Therefore, White has just begun the game with Black in check, and played 0. ... b1-b2, so is not able to play b2-b4 later.

Eventually, when Chess960 becomes played out, we will all be playing Chess4E71, so best to learn it now. There are three diagonals wPb2 may move along, but only one of them works. Rigorous retro reasoning allows all the pawns to make a double move *except* for wPb2. (Author)
Henrik Juel: No comment (2020-08-30)
James Malcom: I think that the simplest possbility to animate this, if Gerd has time that is, would be to allow a pawn to commence a double step fro anywhere. (2020-08-30)
A.Buchanan: Would also need non-standard e.p. (2020-08-31)
Mario Richter: Henrik walking in the footsteps of Epimenides: a comment saying "No comment" :-) (2020-09-20)
A.Buchanan: This is basically the simplest set of rules & conventions to allow chess with any starting arrangement of the orthodox pieces (2020-09-21)
comment
Keywords: Chess4E71, En passant (4), Pac-Man, En passant as mating move
Genre: h#, Retro, Fairies
FEN: 5p1k/4p2p/3p4/2p5/2p5/8/1P6/B1P5
Input: A.Buchanan, 2020-08-30
Last update: A.Buchanan, 2022-06-13 more...
2 - P1379502
Andrew Buchanan
1127 Julias Fairies 19/09/2016
P1379502
(2+2) C+
h=3
Chess4E71
1. h1 Kf2 2. Kh3 Sf7 3. Kh2 Sg5=
play all play one stop play next play all
Author's solution: Schema problem to show the idea. At first glance, h=3 seems completely impossible, even without the confusing fact that Black to move is apparently checking White. But this absurdity is what renders the problem solvable.

Law A1.2 tells us that if the player to move is already apparently checking or even checkmating the opposing king, then he is not allowed to capture that king, and must make another move. The assessment whether the opponent is actually checked or mated is made only when the opponent has the move. In normal chess, such a position is illegal, but it is no more and no less illegal than say wBa1 wPb2. Law A1.2, tells us that we can still play chess. (See Lese Majeste)

In Chess4E71 such "illegal" checks can clearly occur, but only in the starting position. Therefore no moves have been made in the game so far. In particular, bPh3 has never moved. Now Article 3.7b of the Laws of Chess says: "on its first move the pawn [...] may advance two squares along the same file, provided that both squares are unoccupied. So 1. h3-h1! is legal.

Now what happens to the pawn when it arrives on h1? Again we consult the Laws. Article 3.7e says: "When a player, having the move, plays a pawn to the rank furthest from its starting position, he must exchange that pawn as part of the same move for a new queen, rook, bishop or knight of the same colour on the intended square of arrival." The pawn began on the 3rd rank, so it would only promote when it reaches the furthest rank, namely the 8th rank (which it never can attain, under orthodox rules, but that's irrelevant). When it arrives on the 1st rank, it merely remains a pawn. I can almost hear the groans :-)

The rest of the problem solves itself. Or an engine does.

The recognition that BTM is delivering check in what must be the starting position is hardly retro reasoning, so the Article 17A bell does not sound to awake the demon of the Dead Position rule from his slumbers. Hence with a forward stipulation, we don't worry that there is no mate possible after B1 move.
Henrik Juel: groan (2020-08-30)
A.Buchanan: Hark, what’s that I hear? :-) (2020-08-31)
James Malcom: Hark, I hear the angels groan! Oh snark, I head their echos spawn!:-) (2020-08-31)
A.Buchanan: Jacobi does not yet support dummy pawns, alas (2021-05-11)
more ...
comment
Keywords: Chess4E71, Lese Majeste, Dummy Pawn, Minimal, Miniature, Dead Position (not!), Golden Age (Dummy Pawn)
Genre: Fairies
Computer test: HC+ Popeye v4.87. No solution in diagram position for h#3 & 1 solution after key as h#2.5. Only other solution might be if B2 or B3 is h1 without promotion. But bK can only be without a move if in corner or adjacent to bP, which cannot happen after 1. Kg5,Kh5?
FEN: 8/8/7N/8/7k/7p/6K1/8
Input: A.Buchanan, 2020-08-30
Last update: A.Buchanan, 2023-08-04 more...
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