Die Schwalbe

161 problem(s) found in 3826 milliseconds (displaying 100 problem(s)). [COMMENTDATE>=20200919 AND NOT K='Hilfsrückzüger' AND NOT S='Detroit Free Press' AND A='Buchanan, Andrew'] [download as LaTeX]

1 - P1001038
Andrew Buchanan
4v Retros mailing list 21/01/2001
P1001038
(14+1) C+
Last move?
#2
1. 0-0 Kxe2 2. Te1#
R: 1. Ke4-e3
play all play one stop play next play all
Die vorherige Stellung war noch nicht tot, wenn Weiß noch rochieren darf.
AB: First proof of "can castle", without recourse to conventions. (2009-11-22)
A.Buchanan: deadpos doesn't understand about retro logic yet, so does not eliminate R: 1. Ke4xLSBe3? (2022-11-13)
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Keywords: Dead Position, Castling, Rex solus (s), Obvious promotion (L), Last Move?, Type B
Genre: Retro, 2#
Computer test: HC+ Forward Popeye 4.79 DP deadpos
FEN: 8/7Q/8/4BB2/2PP1P2/3NkN2/PP2P1P1/4K2R
Reprints: 13 idee & form 156, p. 5284, 10/2022
Input: Gerd Wilts, 2001-01-25
Last update: A.Buchanan, 2023-12-27 more...
2 - P1006923
Andrew Buchanan
H0657 StrateGems 07-09/2002
in memory of Wolfgang Pauly
P1006923
(3+3) C+
h#2
4 solutions
1) 1. Tf7 Dc1 2. Tce7 Dc8#
2) 1. Te7 Dg1 2. Tcd7 Dg8#
3) 1. Kd8 Dh1 2. Kc8 Da8#
4) 1. Ke7 Df1 2. Kd8 Df8#
play all play one stop play next play all
Suggested by P1001731.
Yuri Bilokin: h#1.5 1...Qf1 2.Kd8 Qf8# (MM) (2021-11-25)
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comment
Keywords: black Bristol, Umnov, Model mate (4), Tempo Move, Echo (4), Miniature
Genre: h#
Computer test: (Popeye WINDOWS98-32Bit-Version 3.75 (2048 KB))
FEN: 4k3/2rr4/8/8/8/8/PK6/Q7
Input: hpr, 2003-01-19
Last update: A.Buchanan, 2021-01-21 more...
3 - P1227253
Andrew Buchanan
N1QCi) Economy Records in Add Unit(s) Problems , p. 4, 06/06/2011
P1227253
(5+5)
Add one unit.
+wDa2
R: Tb2-b1++
play all play one stop play next play all
Impossible treble check, so blocking unit needed on b2 or a2. If the former, then Bl just played R: 1. axb1=T++ & Wh only has a prior move if b2 unit is wS, but then illegal check to sK. So the unit must be added on a2. Last move was not b2-b1=R++ because of prior illegal check from sBb2. So it must be Tb2-b1++ (a capture implies retro pat). So what's on a2? Prior White move was not Kb1-a1, or the check from Tb2 is impossible. So it was L/D allowing L/Db1*a2. If the former, then there is a core cage comprising wKa1 wLb1 wBb3c2d2 sTb2 which can never unlock. So can only be +wDa2, with no problem for wD eventually sliding out.
Economy record for an "Add one unit" problem, type C, in which the unit to add is a Queen.
See http://abrobecker.free.fr/chess/addunits.pdf (2011-12-16)
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Keywords: Type C, Add pieces, Economy record
Genre: Retro
FEN: 8/8/8/8/1P6/rPb5/2PP4/Krnk4
Input: Alain Brobecker, 2011-12-16
Last update: A.Buchanan, 2023-04-13 more...
4 - P1227257
Andrew Buchanan
N18Ci) Economy Records in Add Unit(s) Problems , p. 6, 23/07/2011
P1227257
(9+5)
Add 18 units.
+wBa4b2d2f2h4 +wLc1 +wDc3 +sBa5b6c7d7e7f3g7h5 +sLf8 +sTc4 +sDg3
R: S-d4
play all play one stop play next play all
All pieces will be on board so pawns remain on their original files.
+BPc7d7e7g7 & +WPd2, implying +BBf8. Since BBd5 is out we've +BPb6 +WPb2, entailing +WBc1.
WKb3 is attacked by WNd4, so we need 4 units on the lines to the Ks and one of those lines is blocked by P, so +BPf3 +WPf2. Since all Rs must be out, we have +WPa4h4 +BPa5h5. Lastly, the remaining line interceptions are +BRc4 +WQc3 +BQg3.
Record of the highest number of units to add so that a position becomes legal (Type C, number of units specified).
See http://abrobecker.free.fr/chess/addunits.pdf (2011-12-16)
Henrik Juel: Good problem with well-explained solution (2021-01-17)
A.Buchanan: Thanks Henrik :) (2021-01-18)
comment
Keywords: Type C, Add pieces, Economy record
Genre: Retro
FEN: 8/8/2PNP1P1/1N1b4/1R1n2k1/1K1r4/6Rn/3B4
Input: Alain Brobecker, 2011-12-16
Last update: A.Buchanan, 2023-04-13 more...
5 - P1228018
Enzo Minerva
Andrew Buchanan

Introduction to Proof Games 01/2010
EM, version AB
P1228018
(14+14) C+
Proof game in 9.0
1. e4 f5 2. Lb5 f4 3. Se2 f3 4. 0-0 fxe2 5. e5 exf1=L 6. Dg4 Lc4 7. d3 Kf7 8. Dxc4+ d5 9. exd6ep+ Le6
play all play one stop play next play all
Shortest known proof game showing Valladao-Monteiro (after 8.5 moves - the extra half-move is to move beyond the check, and is the only move which preserves uniqueness of the PG).
Composed for http://abrobecker.free.fr/chess/IntroductionToPGs.pdf
>>> Agreed with Enzo Minerva that this is EM v AB: 24-Dec-2014. (Original is at P1284755.)
Kevin Begley: Partially anticipated, by Enzo Minerva, Best Problems 2005 (which shows Valladao-Monteiro in as many moves, based upon the same idea). (2014-03-01)
A.Buchanan: Thanks for highlighting this, Kevin. I had searched PDB for prior art before composing this one, but Enzo's problem was (and still is) absent. I feel that my little composition does add something more. In mine, the identity-defining Ceriani-Frolkin bishop move is not a capture. And WQ has potentially three routes to its final square, including the CF promotion square, but the two duals are eliminated by the waiting move d3. So, is Enzo still active? I am thinking this partial anticipation probably a case of "AB after EM" but if Enzo is still around I would like to discuss with him out of courtesy. (2014-05-01)
Kevin Begley: Andrew, at best, I see yours as a version. (2014-05-01)
Kevin Begley: Compare to 'P1284755'. Clearly Andrew's version is better (and not only because of the extra move avoiding check in diagram -- which may be forgiven in a proofgame aiming specifically for brevity), however thematically, they are nearly indistinguishable. I leave it for Andrew and Enzo to collaboratively determine the proper credit here. (2014-05-01)
A.Buchanan: Oh for Pete's sake... there's *another*, now I look in WinChloe:
Alexeï GASPARYAN Oakham PG Tourney,
The Problemist Supplement 2009-10
1° Mention d'Honneur.
rnb2rk1/pp1p1ppp/3p4/2q5/1b6/3p4/PPP1PKPP/RNBQ1BNR
PG in 9.0
1.f3 e5 2.f4 Bb4 3.f5 Ne7 4.f6 00 5.f×e7 e4 6.e8=N Qg5 7.Nd6 c×d6 8.Kf2 Qc5+ 9.d4 e×d3ep+ (C+)
Now the date in WinChloe is wrong: what counts is the closing date for the tournament, 31-12-2009 (although the judging was only held in 07-2010, and publication was in 11-2010). Mine was published in 01-2010 (composed on 10-01-2010. I think I fold at this point, and allow Messrs. Minerva & Gasparan to duke it out, if they care. (2014-05-04)
A.Buchanan: @Kevin: and on the subject of versioning. Do you have a link to anything that gives guidelines to relative attribution. The Codex is sketchy (as usual), and I don't know where else to look. (2014-05-04)
Henrik Juel: On versioning:
When inspired by a published problem by AA to improve it, I would write 'hj after AA' if my contribution is large and 'AA, version by hj' is it is small. Of course, 'improve', 'large', and 'small' are not well defined, so it is up to the improver and the editor what to choose, and up to the judge whether an award is warranted.
In the Minerva-Gasparyan-Buchanan case the later authors surely were not inspired by the first, so here I would suggest the following possibilities: anticipated, partially anticipated, and not anticipated, again leaving the final verdict to the judge (2014-05-04)
A.Buchanan: I don't see any fundamental difference between accidental and deliberate partial anticipation. Ultimately the choice is between labeling the problem as "A,version", "A,version B" or "B, after A". I am totally ok with whatever Minerva/Gasparyan eventually determine. However, I don't think that PDB supports "A, version B" currently. (2014-05-05)
A.Buchanan: Not heard anything from Messrs Minerva or Gasparyan. I should rephrase my earlier statement as: "I don't see any fundamental difference between accidental partial anticipation, and acknowledged deliberate versioning, in terms of the set of possible final outcomes." (2014-12-24)
A.Buchanan: Resolved with Enzo :D! (See above!) (2014-12-24)
A.Buchanan: Resolved with Alexey in Facebook yesterday :D! AB: "I would like to ask you: are you ok with the current attribution of my problem?" AG: "Yes I agree." So there we are. Maybe EM & AG will conduct diplomatic negotiations at some point, but that's not my concern :) (2021-10-05)
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Keywords: Valladao Task (swwk), Unique Proof Game, Ceriani-Frolkin Theme (l), Prentos Theme (l), En passant, Castling, Promotion (l)
Genre: Retro
Computer test: Euclide 0.99
FEN: rn1q1bnr/ppp1pkpp/3Pb3/1B6/2Q5/3P4/PPP2PPP/RNB3K1
Reprints: 11 Introduction to Proof Games 03/2010
Input: Alain Brobecker, 2011-12-26
Last update: A.Buchanan, 2021-05-26 more...
6 - P1274528
Andrew Buchanan
15611 Die Schwalbe 261 06/2013
P1274528
(10+5) C+
Proof game in 12.0
1. f4 e5 2. fxe5 Sf6 3. exf6 Ld6 4. fxg7 Lxh2 5. gxh8=L Lxg1 6. Txh7 Le3 7. Txf7 Lxd2+ 8. Dxd2 a5 9. Dxa5 Kxf7 10. Dxc7 Dxh8 11. Dxc8 De8 12. Dxe8+ Kxe8
play all play one stop play next play all
Die Schwalbe 12/2013
MRi: "Nach dem ersten, naturgemäs schlaglosen Zug muss Weiß im Rest der Partie permanent schlagen. Dass sich gleich drei weiße Steine aktiv an dieser Fresserei beteiligen, kommt ebenso überraschend wie der Schnoebelen-Läufer auf h8, den man beim bloßen Blick auf die Endstellung wohl kaum erwartet hätte. Netter (Computer?!)-Fund im Bereich der At-Home-BPs."
HG: Siehe Kommentar zu 15609; hier mit Schnoebelen-Läufer, sK-Rückhehr und sD-Opferzug."
SBa zu 15069 und 15611: "Das dürften die ersten orthodoxen Doppelhomebase it Schnoebelenumwandungen sein. 156909 ist inbesondere weben des genialen Tempozugs Ke7, der die eigentliche Begründung der Umwandlung liefert, viel besser, die andere errinerte eher an Massakerbeweispartien, Nichesdestotrotz will das erstmal konstruiert sein.
A.Buchanan: @Mario: no computer: found by hand over the course of several evenings on a business trip to Mumbai, but I take the suspicion as a compliment! :D (2021-07-18)
comment
Keywords: Unique Proof Game, Homebase (2), Schnoebelen Theme (L), Switchback (k), Ceriani-Frolkin Theme (L), Prentos Theme (L)
Genre: Retro
FEN: rn2k3/1p1p4/8/8/8/8/PPP1P1P1/RNB1KB2
Input: Mario Richter, 2013-07-20
Last update: A.Buchanan, 2021-07-18 more...
7 - P1294321
Andrew Buchanan
www.anselan.com 2001
P1294321
(1+2)
Black to move. Last move?
R: 1. Kb8xSa8
play all play one stop play next play all
Compare P0001033.
Gerald Ettl: steht der sLh5 vielleicht auf h2 ?? (2023-07-02)
SCHRECKE: Why not R: Kb8xLa8? (2023-07-03)
Mario Richter: Wie "SCHRECKE" mit seiner Frage schon illustriert hat: mit dem sL auf h2 wäre das Problem inkorrekt, da neben R: 1. Kb8xSa8 auch R: 1. Kb8xLa8 als letzter Zug möglich gewesen wäre. Grund sind die etwas verwirrenden Dead-Reckoning-Regeln: mit sLh5 kann zuletzt nicht Kb8xLa8 geschehen sein, da in der Stellung wKb8 - sKb6 sLh5 sLa8 wegen der unzureichendes-Material-zum-Mattsetzen-Regel das Spiel schon in dieser Position beendet gewesen wäre, der wK als gar nicht mehr zur Ausführung eines Zuges geommen wäre ... (2023-07-03)
Mario Richter: Dear James, I suggest that you undo last change and put the black bishop back on h5! (2023-07-03)
A.Buchanan: There are 17 valid squares for the wB. Got to be on a light square for reasons given. Also it can't occupy or attack c8. And can't be attacking a8 because BTM. I think h5 selection was random, but could argue for any. (2023-07-04)
A.Buchanan: Or maybe bBa4, with which White by his last move avoided a completely sound #12. (2023-07-04)
Gerald Ettl: Dann waere es vielleicht ganz sinnvoll man schreibt die Bedingung unter das Diagramm. (2023-07-04)
A.Buchanan: Hi Gerald, it's not a condition, it's a FIDE rule since 1997, invented by a problemist who is also a rules committee member (Igor Vereschchagin) and approved by the rules committee (headed by FIDE Head International Arbiter Stewart Reuben), backed up by a WFCC convention since 2015 (Kjell Widlert & Michel Caillaud, responding to a request from some endgame studiers who understood that it was a real thing. Like 50M rule, it applies by default for retro problems. And the PDB keywords here give the game away anyway. If it was a forward stipulation, then I would indeed add a stipulation, e.g. P1208623. Please enjoy the madness that is DP rule :) P.S. I have found recently that it was really invented by Shakespeare. (2023-07-04)
Gerald Ettl: Ich spiele nicht nach den FIDE-Regel. (2023-07-04)
Olaf Jenkner: Allright.
https://www.skat-online.com/regeln-hilfe/regelwerk/internationale-skatordnung.html (2023-07-05)
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Keywords: Type B, Last Move? (KxS), Dead Position, Economy record (Last Move? Type B), Rex solus (W), Aristocrat, Miniature, Minimal
Genre: Retro
FEN: K7/8/1k6/7b/8/8/8/8
Reprints: Retros mailing list 20/02/2007
Input: A.Buchanan, 2015-01-07
Last update: James Malcom, 2023-07-03 more...
8 - P1323914
Andrew Buchanan
PDB Website 14/08/2016
P1323914
(16+15) C+
a) White to move. Last move?
b) KBP in 4.0
b) 1. f4 Sc6 2. Kf2 Se5 3. Kg3 Sg4 4. Kxg4 Tb8
a) R: 1. Ta8-b8
play all play one stop play next play all
See also: P1012898 & P1388527
Henrik Juel: Even though obvious, the a) solution should be included
a) Ta8-b8 (2016-08-15)
A.Buchanan: Can't get both solutions to be animated here, due to hidden interactions with stipulation text (2021-04-14)
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Keywords: Unique Proof Game, Last Move?, Type B
Genre: Retro
Computer test: C+ Retractor 2.0 Last move? C+ Euclide 1.01 SPG
FEN: 1rbqkbnr/pppppppp/8/8/5PK1/8/PPPPP1PP/RNBQ1BNR
Input: A.Buchanan, 2016-08-13
Last update: A.Buchanan, 2021-04-14 more...
9 - P1324999
Andrew Buchanan
9v Problemas 12, p. 285, 10/2015
after Hauke Reddmann
P1324999
(2+2)
Illegal position.
White to move.
How does the game end?

Author's "Solution" from Problemas magazine [edited]:
"White has no move, and is not in check. But for stalemate to apply, and end the game, it basically requires that the move producing the position was legal (see Law A5.2a). Not only is the position illegal, but no legal last move exists, even from a previously illegal position! So we are stuck in some kind of limbo. The result can perhaps be described as “nearly stalemate”.
Hauke Reddmann described a position like this as “dividing by zero”. It's an exception to the general observation that one can continue to play chess if the wrong player is in check. It seems odd to insist that only the final move in a game has to be legal, but that’s what the rules do. And I think that’s as far down the rabbit hole as we should go today."
Not Thema Null, because set play does not already achieve the stipulation.
A.Buchanan: The forward rules can apply perfectly well to illegal positions (e.g. set play, where we never concern ourselves with the position's legality). But a lacuna comes where a position with no precursor position is delivering mate, stalemate or DP. A #0 should work as well as a #2. In all cases, the FIDE Laws currently require that the prior move (and only that move) be legal. The Law is about catching errors/cheating otb, so I think the Codex should ensure it does not get carried over to problem chess. This problem will then lose its point, but it will have served its purpose and it can be retired to Golden Age, much to Henrik's relief :) (2023-12-15)
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Keywords: Lese Majeste, Illegal position, Dead Position, Miniature
Genre: Retro
FEN: 8/8/8/8/8/nk6/P7/K7
Input: A.Buchanan, 2016-09-06
Last update: A.Buchanan, 2019-12-09 more...
10 - P1346927
Andrew Buchanan
ID01 chess.stackexchange.com 10/10/2017
P1346927
(16+16) C+
White to move. Dead position with 32 pieces.
R: 1. b5-b4,c6-c5,d7-d6,g6-g5
play all play one stop play next play all
BTM: living or stalemate, depending on ep convention
WTM: 32 moves none of which relieve the looming pat. And 2 e.p. moves which are illegal considering Lf8. So by dead position rule, the game is drawn. See P1182050 & P1398255.
Retracting c6-c7 gives ID02 Type C from that post.
HBae: with wQg2: Kc6-c7 not possible (2022-01-11)
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comment
Keywords: Dead Position, Construction record, Capture-free, Type B, En passant
Genre: Retro
Computer test: HC+ Popeye v4.87 ~1 halfduplex & h#1 halfduplex both 0 solutions
FEN: bqn1KN2/rrk1pB2/nb1pPp1p/p1pP1PpP/PpP3P1/1P2N1R1/4Q3/1R4B1
Input: A.Buchanan, 2018-02-18
Last update: A.Buchanan, 2023-12-17 more...
11 - P1348600
Andrew Buchanan
chess.stackexchange.com 23/3/2018
P1348600
(12+12) C+
PG in 20.0
1. d4 c5 2. f4 e5 3. f5 d5 4. Lf4 Le6 5. fxe6 exf4 6. e4 f5 7. e5 c4 8. Ld3 Lc5 9. dxc5 cxd3 10. c4 a5 11. b4 a4 12. Db3 axb3 13. a4 b5 14. a5 h5 15. g4 Th6 16. g5 d4 17. gxh6 g5 18. h4 g4 19. Ta4 Dg5 20. hxg5 bxa4 example
play all play one stop play next play all
A shortest game to reach 16 passed pawns
Henrik Juel: Euclide 1.01 confirms that no shorter proof game exists
It seems that the moves are unique, so a challenging part b) suggests itself: How many solutions? (2018-03-27)
A.Buchanan: Thanks, Henrik. Your b) would be challenging indeed! Usually if I make a problem "how many solutions?", the purpose of the problem is to showcase some combinatorial identity, and the play would be structurally simpler.
A different direction is to ask: how many *diagrams* exist that could illustrate the same point: 16 passed pawns in 20.0 moves? I think the answer, including this one, is 12.
Another much harder question is whether one can push the surviving officers around to make a longer but unique proof game. (2018-03-28)
Henrik Juel: 16 passed pawns come in (at least) two varieties
1. A pawn position where all pawns could promote without further captures
2. A pawn position where PxP captures (except possibly ep) are no longer possible
Andrew's definition is probably the latter (2018-03-28)
A.Buchanan: Sorry I don't understand this distinction. (2018-03-28)
Henrik Juel: They are not mutually exclusive, 2 implies 1
Type 1 would apply to your PG, also if the white pawns on the c and e files were lowered to c2,c3 and e2,e3
In type 1 'passed' is interpreted as 'allowing 16 free promotions'; it is equivalent to a game with 8 pawn captures, 1 from each file
To reach type 2, some pawn may have to advance further (2018-03-28)
A.Buchanan: OIC: in the context of playing the game, definition 2 is what counts, because no PxP captures are possible. The only question in people'e minds in stackexchange is whether doubled pawns can count as being passed. The assessment is that they can. (2018-03-28)
Moldenhauer: Computerprüfung: Cooked Diagrammstellung Stelvio 1.31.
Keine Lösung: BP 19.5.
Beispiel: 1. b4 a5 2. d4 a4 3. e4 b5 4. Bd3 c5 5. f4 c4 6. f5 cxd3 7. Bf4 d5
8. c4 e5 9.Qb3 Be6 10. fxe6 Bc5 11. dxc5 axb3 12. a4 d4 13. a5 exf4
14. Ra4 bxa4 15. g4 h5 16. g5 Rh6 17. gxh6 g5 18. e5 g4 19. h4 Qg5 20. hxg5 f5 (2023-06-18)
A.Buchanan: Thanks Moldenhauer. This is "obviously" a non-unique proof game, but there's no syntax in stipulations to distinguish between them. There is also sometimes the notion that a non-unique PG must force some thematic content, but that's not the case here, as the content is visible in the target diagram. So I interpret your Stelvio as C+ for this humble problem. Thanks again. (2023-06-21)
comment
Keywords: Construction record, Non-Unique Proof Game
Genre: Retro
Computer test: Computerprüfung: Non-unique solution Diagrammstellung Stelvio 1.31. Keine Lösung: BP 19.5
FEN: rn2k1n1/8/4P2P/P1P1PpPp/pPPp1pp1/1p1p4/8/1N2K1NR
Input: A.Buchanan, 2018-03-27
Last update: A.Buchanan, 2023-06-21 more...
12 - P1359492
Andrew Buchanan
17464 Die Schwalbe 291, p. 492, 06/2018
to Torsten Linß
P1359492
(2+4) C+
h#6
1. f3 Kg4 2. f2 Kf3 3. c1=L Ke2 4. f1=L+ Kd1 5. Lc4 Kxc1 6. La2 Lc3#
play all play one stop play next play all
See P1316696 and P1359493
Henrik Juel: Pg2 prevents cooks ending 5... Kxc2 6.La2 Lc3# (2019-01-12)
A.Buchanan: I just realized I chose the dedications of these two problems the right way round luckily: L for Linß and S for Schnoebelen :D (2019-01-12)
VL: Reprint: (2) Problemas 37, p.1232, 01/2022 (2022-01-23)
comment
Keywords: Minimal, Schnoebelen Theme (l), Prentos Theme (l), Ceriani-Frolkin Theme (l), Miniature, Promotion (ll)
Genre: h#
Computer test: Popeye WINDOWS98-32Bit-Version 3.77 (8192KB)
FEN: 8/8/8/7K/5p2/8/2pB2p1/k7
Input: Felber, Volker, 2019-01-12
Last update: A.Buchanan, 2021-01-21 more...
13 - P1359493
Andrew Buchanan
17465 Die Schwalbe 291, p. 492, 06/2018
to Philippe Schnoebelen
P1359493
(2+4) C+
h#6
1. c1=S Lxe7 2. d3 Kf2 3. d2 Ke3 4. d1=L Kd2 5. Lb3 Kxc1 6. La2 Lf6#
play all play one stop play next play all
See P1316696 and P1359492
And see P1375440 for a fairy version
Mario Richter: Henrik wrote: "The term Schnoebelen theme first was used in proof games".

Even if it's like fighting against windmills, "Schnoebelen promotions" were *NOT* first used in proof games, but in orthodox retros. Ceriani invented the theme in 1948, maybe even before Philippe was born!
See my post in the Retros Mailig List:
https://pairlist1.pair.net/pipermail/retros/2008-December/002752.html (2019-01-13)
VL: Reprint: (3) Problemas 37, p.1232, 01/2022 (2022-01-23)
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Keywords: Minimal, Promotion key (s), Schnoebelen Theme (s), Prentos Theme (s), Ceriani-Frolkin Theme (s), Miniature, Promotion (sl)
Genre: h#
Computer test: Popeye WINDOWS98-32Bit-Version 3.77 (8192KB)
FEN: 8/4p3/5B2/8/3p4/8/2p5/k5K1
Input: Felber, Volker, 2019-01-12
Last update: A.Buchanan, 2021-01-21 more...
14 - P1368554
Andrew Buchanan
OzProblems.com 16/10/2019
P1368554
(4+3) C+
Gewinn
1. Sd3! Kf8 2. Se3 Sg6+ 3. Kd4 Td8+ 4. Kc3 Tc8+ 5. Sc4 Kg7 6. Sf2 Sh8 7. Tf1 Sf7 8. Se4 Td8 9. Sf6 Sg5 10. Se3 Ta8 11. Kb4 Tb8+ 12. Kc4 Tc8+ 13. Kb5 Tb8+ 14. Kc6 Ta8 15. Sfd5 Ta3 16. Kb5 Se4 17. Te1 Sg5 18. Kb4 Ta2 19. Tf1 Kg6 20. Tf6+ Kh5 21. Kb3 Ta7 22. Sf4+ Kh4 23. Se2 Tb7+ 24. Kc4 Sf7 25. Tf1 Kg5 26. Sd4 Se5+ 27. Kd5 Sd3 28. Se6+ Kg6 29. Sf8+ Kg5 30. Ke4 Sc5+ 31. Kd4 Sd7 32. Se6+ Kg6 33. Sd5 Ta7 34. Se7+ Kh5 35. Tg1 Ta4+ 36. Ke3 Tg4 37. Ta1 Sb6 38. Kf2 Sd7 39. Ta8 Tc4 40. Tg8 Tc2+ 41. Ke3 Tc3+ 42. Kf4 Tc4+ 43. Kf5 Kh4 44. Sf4 Sf6 45. Tg2 (thr 46.Sg6#) Tc5+ 46. Kxf6 Tc6+ 47. Kf5 Tc5+ 48. Sed5 (thr 49.Tg4#) Txd5+ 49. Sxd5 (switch to Syzygy DTM) Kh3 50. Sf4+ Kh4 51. Tg4#
Compare 44. ... Tc5+ which gives a longer DTM at the cost of a slightly sub-optimal DTZ. 45. Sed5 (thr 46.Tg4#) Txd5+ 46. Sxd5 (switch to Syzygy DTM) Kh3 47. Tc8 Kg3 48. Ke6 Sb6 49. Sxb6 Kf2 50. Sc4 Ke1 51. Td8 Ke2 52. Td2+ Ke1 53. Kd5 Kf1 54. Ke4 Kg1 55. Kf3 Kh1 56. Kg3 Kg1 57. Td1#
play all play one stop play next play all
According to the Syzygy tablebase, *any* move wins for White except the silly 1. Sa2??
However, the tablebase does not know about castling!
The quickest winning move 1. Sd3!? would be defeated by 1. ... 0-0-0!? which attacks Sd3 and threatens the skewer Re8+. After this, White can only draw - or even loses after 2. Sc1??
But by a simple retro argument, Black cannot castle.
Since this retro point is essential to the solution, we have a retro problem, and hence the 50 move rule, which by Codex default is disengaged, is switched on.
When working with the 50 move rule, the key concept is not the number of moves to mate, but the number of moves to the first capture, pawn move or checkmate, known as DTZ.
All the alternatives to 1. Sd3 take more than 50 moves to force the first capture. The closest are 1. Sc3 & Se3 which according to Syzygy require exactly 50.5 moves, so seem *just* too slow. (For positions close to the cut-off, one has to be careful about *rounding*, see https://syzygy-tables.info/metrics. The number of half-moves for DTZ can be n or n+1. In fact here, after 1. Sc3/Sf3, the zeroing move is at its earliest White's 52nd move, not 51st.)
By the retro property therefore *only* 1. Sd3!, which requires 45 moves to force the first capture, can win. So this removes all the cooks for the first White move.

Lomonosov DTM #59: 1. Nd3!! Kf8!! 2. Ne3! Ng6+! 3. Kd5 Rd8+ 4. Kc4 Rc8+ 5. Kb5 Rb8+ 6. Ka6 Kf7 7. Nc5 Ne5 8. Nd5 Re8 9. Kb7 Nc4 10. Rf1+ Kg7 11. Kc6 Re5 12. Nd3 Re6+ 13. Kc5 Ne5 14. N3f4 Nd7+ 15. Kb5 Rd6 16. Nc7 Kf7 17. Nfd5+ Kg6 18. Ne7+ Kg5 19. Ncd5 Kg4 20. Rf4+ Kg5 21. Rf2 Kg4 22. Ne3+ Kg5 23. N7d5 Kg6 24. Rf1 Nf6 25. Nf4+ Kf7 26. Nc4 Rd8 27. Ne5+ Kg8 28. Rg1+ Kh7 29. Kc6 Rc8+ 30. Kd6 Re8 31. Re1 Ra8 32. Rh1+ Kg8 33. Ke7 Ra4 34. Rg1+ Kh7 35. Ne6 Nd5+ 36. Kd6 Nf4 37. Nc5 Rd4+ 38. Ke7 Rd2 39. Rg4 Rf2 40. Ncd7 Nd5+ 41. Ke6 Nf4+ 42. Kd6 Rd2+ 43. Ke7 Nd5+ 44. Kf8 Kh6 45. Rh4+ Kg5 46. Nf3+ Kf5 47. Nxd2 (zeroing 50M) Nc7 48. Re4 Ne6+ 49. Ke7 Nf4 50. Nf6 Ng6+ 51. Kf7 Ne5+ 52. Kg7 Kg5 53. Nf1 Kf5 54. Ne3+ Ke6 55. Nc4 Ke7 56. Rxe5+ Kd8 57. Rc5 Ke7 58. Rd5 Ke6 59. Re5# 1-0.
http://www.ozproblems.com/walkabout/walkabout2019#WA1610
https://www.chess.com/blog/Rocky64/a-heraldic-endgame-tablebase-composition

The school shield which inspired the problem:
http://www.calvert-trust.org.uk/images/colour.jpg
Henrik Juel: With White to move, last move was made with Ta8 or Ke8, so Black may not castle
An endgame connaisseur may supply the solution... (2019-10-25)
James Malcom: It is now supplied, Henrik. :) I worked through the Sygyzy tablebase, move by move, to get the computer recommended line. (2020-10-09)
A.Buchanan: Thanks James for this hard work to record a solution. Alas there is not just a single recommended line - White has a choice as early as W3. I wonder too if there is a DTM line which is faster than #57, and still clears the DTZ hurdle although maybe not as quickly as B45 as here. There is no DTM engines for 7 pieces yet.
What is certain is that the key works, and is unique. The exactly details of the best mating line remain to be revealed by improving technology. (2020-10-09)
A.Buchanan: For example, 2. Nc5 has DTZ 90, compared to the "superior" 2. Ne3 DTZ 88. However, if you keep picking the top move all the way through, then the final DTZ is in fact checkmate! I haven't all the Black choices though, but there aren't that many of them (2020-10-09)
A.Buchanan: The Lomonosov tablebase is DTM, and is available for free on Android. Today I found a PC app called Blue Stacks which emulates Android. According to Lomonosov, the position is #59, compared to Syzygy's DTZ offering #57 via zero at B45. When I run through the L. indicative solution (very quick to download and grab all of it), it is close to S.'s choices and all the mainline positions are safe from 50M. The zero is at W47, and the final mate is attractive in the middle of the board.
The real questions are:
(1) Is the #59 sound from 50M perspective? Or can Black force White to delay a few moves in order to avoid 50M trouble somewhere?
(2) How dualized is the solution? How does 50M play into pruning that?
What is clear is that both tablebases agree the solution begins 1. Nd3!! Kf8!! 2. Ne3! Ng6! (2020-10-10)
A.Buchanan: James' Syzygy solution had seemed a little odd, because it seemed to go against Syzygy's assertion that DTZ=n means that zeroing happens at n or n+1 ply (it's not exact because of Syzygy's rounding of the units bit of the integers, which apparently saves a vast amount of data, and is allegedly "safe"). But James's solution has zeroing at n-1. If Black was indeed forced to zero prematurely in this way, this would show a bug in Syzygy.

In no sense is this a criticism of James: for whose talent, hard work & existence I am incredibly grateful. But it turns out there is a tiny issue in the solution he posted, just before DTZ=0.

Quarantine lockdown in Hong Kong has given me a chance to look at the position after W44, https://syzygy-tables.info/?fen=6R1/3nN3/8/5K2/2r2N1k/8/8/8_b_-_-_0_1, Black has two choices Tc5+ & Sf6. James chose the first for simplicity, as sensibly he always did, but 45. Sed5 threatens 46. Tg4#. The only way to avoid this 45. ... Txd5+ prematurely zeroing. But Syzygy makes no promises about DTM - it just happens that the random path that James found has mate as the zeroing move! This is not typical, so a better illustrative solution has 44. ... Sf6. With best play by both sides, I think this results in mate at W51.

How to compare this with the Lomonosov solution with mate at W59? How is it possible that Syzygy, with the extra constraint of avoiding 50M draw, has found a *shorter* mate? If you think about it, there is no issue here. Syzygy is only focusing on DTZ, and there are many points in the long solution at which there are choices of equal DTZ. What Lomonosov tells us is that Black can somehow force a Syzygy branch which gives #59 or longer. For 6 or 7 pieces, we just don't have the visibility in Syzygy to find that DTM path. That is the explanation. However for 5 pieces, Syzygy also gives us the DTM value, and as long as one has escaped 50M range, it makes case to switch to that as soon as 5 pieces are reached. (2022-08-05)
A.Buchanan: As problemists, what we would really like to know is the minimum number of moves to mate, while not falling foul of 50M. Even with both DTZ & DTM values known, this is not easy to find. Here is a toy example to show one difficulty: https://syzygy-tables.info/?fen=7k/8/7K/4P2R/8/8/8/8_b_-_-_0_1 Black's forced move leads to DTZ=1 DTM=3, but White must choose which he wants to achieve, as they are mutually exclusive. If the 50M clock is low, 1.e6 gives DTM=16. But otherwise 1.Rf5 gives DTM=2. Now White will know which he wants, but Black is usually free to decide whether to defend the DTZ or the DTM or potentially to delay the commitment. The tactical richness of a position is not captured by simply the DTZ & DTM values (2022-08-05)
A.Buchanan: OK it turns out that what I'd been arguing for already exists to some extent: it's called DTM50 - see http://galen.metapath.org/egtb50/ (2022-08-05)
comment
Keywords: Cant Castler, Aristocrat, 50 move rule, Miniature
Genre: Retro, Studies
Computer test: www.syzygy.com
FEN: r3k2n/8/8/4K3/8/8/8/2NNR3
Reprints: www.chess.com 17/10/2019
Input: A.Buchanan, 2019-10-25
Last update: A.Buchanan, 2022-08-05 more...
15 - P1370911
James Malcom
Andrew Buchanan

(4) MatPlus.net Forum Retro/Math 21/12/2019
P1370911
(12+14)
PG in 12.5
(-:
1. e4 d5 2. e5 Dd6 3. exd6 Kd7 4. dxe7 Kc6 5. Lb5+ Kxb5 6. c4+ Kxc4 7. e8=T Kd3 8. Df3+ Kc2 9. d3 Lh3 10. Ld2 Lxg2 11. Lb4 Lxh1 12. Sc3 Lg2 13. 0-0-0-0-0-0#
play all play one stop play next play all
http://matplus.net/start.php?px=1609818957&app=forum&act=posts&fid=xshowr&tid=2402&pid=20379#n20379
Objective: Staugaard (Pam-Krabbé) castling as mating move.
more ...
comment
Keywords: Unique Proof Game, Staugaard castling, Joke, Prenix, Promotion (T), Castling as mating move, Superseded by (P1385595)
Genre: Retro, Fairies
Computer test: C+ Natch 3.1 has no solutions in 12.5 moves & 1 solution for first 12.0 moves. (H.Juel)
FEN: rn3bnr/ppp2ppp/8/3p4/1B6/2NPKQ2/PPk1RPbP/R5N1
Input: A.Buchanan, 2019-12-23
Last update: James Malcom, 2022-02-26 more...
16 - P1375286
Andrew Buchanan
James Malcom

PDB Website 30/4/2020
P1375286
(6+3)
#2
(-:
1. dxc7ep! b4 2. c8=D,T#

R: 1. ... c8-c6?! and earlier c8=sB?!
play all play one stop play next play all
Supersession of P1380851

Superseded by P1380851

The 2018 FIDE laws state: "3.7.2 on its first move the pawn may move as in 3.7.1 or alternatively it may advance two squares along the same file, provided that both squares are unoccupied."

Hence Black's newborn 8th rank pawn, which has never been moved before, reserves the right to commence a double-step on its first move, and likewise White receives the right to capture it en passant as they do with a 7th rank pawn.
Henrik Juel: This un-dummy-pawn is like a pawn created on c8 by the Einstein condition
The retroplay looks wrong, what about 1... d8-d6!? 2.d7-d8=sB!? c6xYb5 (2020-04-30)
James Malcom: That makes much more sense Henrik. I have edited it accordingly. (2020-04-30)
A.Buchanan: You don't like Adrian's (: haha? What about :) then? In heraldic terms, it would be described as "regardant". See 270 on https://www.heraldica.org/cgi-bin/atlas.pl?12. I don't know the word for "non-regardant", which is the default direction for the head, e.g. most of the others on that page.
We could replace wBa6a7 with wSa6, but alas having the 3rd knight is non-thematic & distracting. The other thing I would've liked to do is empty b2 so the promotion is forced to be to D. Such a tiny problem should have precision promotion. Needs more thinking. (2020-05-01)
James Malcom: UPDATE: The position has been edited to have one less piece and a precise queen promotion. (2020-10-12)
A.Buchanan: There is dialogue here which is now orphaned by a change of diagram with new matrix. Suggest we revert to the older diagram and mark it superseded by a new PDB entry here (2020-10-12)
James Malcom: I agree-it is now done. (2020-10-12)
more ...
comment
Keywords: En passant as key, Joke, Joke promotion (b), Tolerated dual promotion (D/T), Promotion (D/T), Superseded by (P1380851)
Genre: 2#, Retro
FEN: k7/PN1N4/PKpP4/1p6/8/8/8/8
Input: James Malcom, 2020-04-30
Last update: A.Buchanan, 2022-09-18 more...
17 - P1375440
Andrew Buchanan
17465v Die Schwalbe 291, p. 492, 06/2018
to Rewan Demontay
P1375440
(3+4) C+
h#6
White Dummy f2
1. c1=DU Lxe7 2. d3 Kf1 3. d2 Ke2 4. d1=L Kd2 5. Lb3 Kxc1 6. La2 Lf6#
play all play one stop play next play all
Added 1 Dummy to P1359493, and changed the dedicatee. My luck with this little series continues to hold: the dedicatee's surname begins with a D!
James Malcom: Andrew, I just found this today-I thank you very much, but perhaps it holds no more, for my true name is known now! (2020-10-28)
comment
Keywords: Miniature, Promotion key (du), Schnoebelen Theme (du), Prentos Theme (du), Ceriani-Frolkin Theme (du), Promotion (du,l)
Pieces: i = Dummy (DU)
Genre: h#, Fairies
Computer test: Popeye 4.81
FEN: 8/4p3/5B2/8/3p4/8/2p2I2/k5K1
Input: A.Buchanan, 2020-05-03
Last update: A.Buchanan, 2021-05-01 more...
18 - P1375654
Andrew Buchanan
(2) MatPlus.net Forum 09/05/2020
in memory of Wilhelm Steinitz
P1375654
(13+14) C+
PG in 8.0 (-:
1. f4 a5 2. f5 a4 3. f6 a3 4. fxe7 axb2 5. exf8=B! bxa1=L 6. Lb2 Ke7! 7. Lf6+ Ke6! 8. Sc3 Dxf8!
play all play one stop play next play all
Henrik Juel: The solution is almost given away by the keywords
1.f4 a5 2.f5 a4 3.f6 a3 4.fxe7 axb2 5.exf8! bxa1=L 6.Lb2 Ke7 7.Lf6+ Ke6 8.Sc3 Dxf8
Even though Black captures the white man on f8, promotion to DTLS will not work
First Schnoebelen with dummy pawn as the captured man, I would think
Very good, Andrew (2020-05-08)
Henrik Juel: Another first:
Never before was a problem commented in the PDB before it was published... (2020-05-08)
James Malcom: When Andrew messaged me this asking about a PG with two dummies, I came back almost right away with the same idea, albeit in a flawed form-1. a4 f5 2. a5 f4 3. a6 f3 4. axb7 fxe2 5. bxa8=Q exd1 6. Ke2 e6 7. Ke3 Qg5+ 8. Kd4 Qxg2 9. Qf3 Qxh1 10. Qxd1. Great minds think alike after all! The best way. I think, to have two dummies is to have one per side and have both kings make the same journey. An idea to make it all unique is the problem though. (2020-05-08)
A.Buchanan: Haha Henrik thank you. Well I'm in lockdown in Singapore, and it was 9-May already when I posted in Matplus. (2020-05-09)
A.Buchanan: Can claim that this is not Schnoebelen because the pawn wasn't promoted! Just remained as a pawn! But I'm sure the Schnoebelen theme was interpreted in a looser sense in 1860s. Although exponents in that era would have been baffled as to *why* the theme was termed "Schnoebelen", as Philippe was not yet born. (2020-05-09)
Henrik Juel: I am sorry to learn about the Singapore lockdown, but here the merriment has no bounds (apart from the notational dilemma: exf8 is not a promotion and still the PDB animation requires exf8=B) (2020-05-09)
Olaf Jenkner: If you consider each pawn move onto the 8th rank as a promotion then we have the Schnoebelen. (2020-05-09)
A.Buchanan: This is not "non-standard material", removing that keyword. (2022-01-26)
more ...
comment
Keywords: Unique Proof Game, Schnoebelen Theme (B), Phoenix (l), Prentos Theme (B), Ceriani-Frolkin Theme (B), Dummy Pawn, Golden Age (Dummy Pawn), Promotion (Bl)
Genre: Retro
Computer test: Jacobi v0.7.4 2020-05-08
FEN: rnb2qnr/1ppp1ppp/4kB2/8/8/2N5/P1PPP1PP/b2QKBNR
Input: A.Buchanan, 2020-05-08
Last update: A.Buchanan, 2023-08-04 more...
19 - P1377152
J. B. McKim
Andrew Buchanan

MatPlus.net Forum 20/6/2020
JBMcK, correction AB
P1377152
(6+4) C+
#2
1. Sc7! zz
1. ... Lxe7 2. Sb5#
1. ... Lxc7 2. Sc8#
1. ... Kxc7 2. Df4#
1. ... Kxe7 2. Dc5#
play all play one stop play next play all
Correction of 317 American Chess Journal, p. 49, 07-08/1877
See P1213947
A.Buchanan: 2-for-1 flight exchange + sacrificial key, together with the asymmetrical position perhaps compensates for the cook-blocking tied pawn pair on a4/a5 (2021-07-06)
more ...
comment

Genre: 2#
Computer test: Popeye 4.61
FEN: 3bB3/4N3/K2k1p2/p2N1Q2/P7/8/8/8
Input: A.Buchanan, 2020-06-20
Last update: A.Buchanan, 2021-07-06 more...
20 - 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...
21 - 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...
22 - P1380440
James Malcom
Andrew Buchanan

MatPlus.net Forum 23/09/2020
P1380440
(10+1) C+
#4
A retro try is:
1. c4? Kxd3 2. Sc3 Kd4 3. Ld6 Kd3 4. 0-0-0#?
2. ... Kc2 3. c5 Kd3 4. 0-0-0#?
but wK has moved, so neither line works.

1. f3! Kxd3 2. Kf2 Kc2 3. Se3+ Kd3 4. Td1#

R: 1. Kc1xLc2 Lb1xTc2,Lb1xSc2
So OK for WTM
play all play one stop play next play all
Henrik Juel: Compared to James's P1380439:
1. Last move could be Kc1xLc2, so White has the move
2. White may not castle, so
1.c4? Kxd3 2.Sc3 Kd4 3.Ld6 Kd3 4.0-0-0, 2... Kc2 3.c5 Kd3 4.0-0-0 is a try
The solution is
1.f3 Kxd3 2.Kf2 Kd2 3.Se3 Kd3 4.Td1#
2... Kc2 3.Se3+ Kd3,Kd2 4.Td1#
C+ Popeye 4.61
Very nice, James and Andrew (2020-09-29)
A.Buchanan: Thanks Henrik - Belen precondition of bKc1 was satisfied 1.0 move ago. From that position there is a sound #5 but position is clunky and not Meredith.
You didn’t fall into the trap of thinking Black has no last move: there is a dualized solution with BTM waiting for you if you did. (2020-09-30)
James Malcom: Haha, yeah. I fell for Andrew's trap, hook, line, and sinker! :-) (2020-09-30)
comment
Keywords: Rex solus, Belen Theme (Normal & Anti-), Cant Castler
Genre: n#, Retro
FEN: 8/8/8/8/8/BPPP4/PPk2P2/R2NK3
Input: A.Buchanan, 2020-09-29
Last update: A.Buchanan, 2021-07-17 more...
23 - P1380852
James Malcom
Andrew Buchanan

MatPlus.net Forum 12/10/2020
after Josef Cumpe
P1380852
(1+7)
Last two moves?
(-:
R: 1. 0-0-0+ a7-a8=sT
play all play one stop play next play all
See P1234039 and P1375777
The joke here is that pawns may promote to enemy officers (but not to pawns or kings)
Henrik Juel: R: 1... 0-0-0+ 2.a7-a8=sT! (2020-10-12)
A.Buchanan: Maybe this is a moderate joke where we allow promotion to Bl officers, while son-of-P1375777 can be the extreme joke where promotion to any Bl unit is allowed (i.e. pawn & king too), including in the history of the game. What would Josef Cumpe think? :-) He and I are both dressed as clerics in out chesscomposers' blogspot pics: http://chesscomposers.blogspot.com/2012/08/august-16th.html. Perhaps he was a real one though? (2020-10-13)
comment
Keywords: Last Moves?, Joke promotion (t), Rex solus, Type C, Castling in the retro play, Joke, Promotion in the retro play (t), Castling (sg)
Genre: Retro
FEN: 2kr2K1/1p1p1npr/8/8/8/8/8/8
Input: A.Buchanan, 2020-10-12
Last update: A.Buchanan, 2023-08-15 more...
24 - P1380882
James Malcom
Andrew Buchanan

PDB Website 14/10/2020
after Josef Cumpe
P1380882
(2+7)
Last two moves?
(-:
R: 1. ... 0-0-0+ 2. a7-a8=sT
play all play one stop play next play all
See P1234039, P1375777 and P1380852.
The joke here is that pawns may promote to *any* unit (friend or enemy; officer, king or pawns).
Henrik Juel: R: 1... 0-0-0+ 2.a7-a8=sT
not 2.e7-e8=sK, because then sTa8 would have moved, and castling not allowed (2020-10-14)
A.Buchanan: Exactly, Henrik. Also: sB on 7th rank could retract to 8th rank, so we need sT instead (2020-10-14)
more ...
comment
Keywords: Last Moves? (2), Type C, Castling in the retro play, Non-standard material (tt), Joke, Joke promotion (t), Promotion in the retro play (t), Minimal, Castling (sg)
Genre: Retro
FEN: 2kr3K/1r1r1qrR/7p/8/8/8/8/8
Input: A.Buchanan, 2020-10-14
Last update: A.Buchanan, 2023-08-15 more...
25 - P1380896
Andrew Buchanan
MatPlus.net Forum 12/10/2020
P1380896
(13+13) C+
PG in 6.5
(-:
1. b4 g5 2. b5 g4 3. b6 g3 4. bxa7 gxh2 5. axb8=sS! hxg1=wT! 6. Txh7 Txh7 7. Th1
play all play one stop play next play all
The joke here is that pawns may promote to foreign units.
Henrik Juel: The testers probably do not work here, but this seems unique
1.b4 g5 .. 4.bxa7 gxh2 5.axb8=sS hxg1=wT 6.Txh7 Txh7 7.Th1 (2020-10-14)
A.Buchanan: According to Joost De Heer, WinChloe has a category “promotions adverses”, and under this, the problem is C+. Looking now for a full Homebase without utilising promotion to enemy pawn, which makes it too easy (2020-10-15)
comment
Keywords: Unique Proof Game, Joke, Joke promotion (sT), Homebase (w), Phoenix (s), Prenix (T), Impostor (sT)
Genre: Retro, Fairies
Computer test: C+ WinChloe
FEN: rnbqkbn1/1ppppp1r/8/8/8/8/P1PPPPP1/RNBQKB1R
Input: A.Buchanan, 2020-10-14
Last update: A.Buchanan, 2022-09-18 more...
26 - P1381285
Andrew Buchanan
James Malcom

MatPlus.net Forum 25/10/2020
P1381285
(5+7) C+
#3
Bosma
1. Tf5+! Sxf5+ 2. Se4+! Sxe4 3. De6#
play all play one stop play next play all
James Malcom: I've added in the solution now. (2020-11-02)
Henrik Juel: Thanks, James
I cannot test the problem, but it seems OK (2020-11-02)
A.Buchanan: Thanks Henrik: it's C+ according to WinChloe (2020-11-03)
comment
Keywords: Aristocrat, Bosma
Genre: 3#, Fairies
Computer test: C+ WinChloe v3.51
FEN: 3r2R1/3Q4/3K1k2/2n1R3/1b6/6n1/3N3q/3r4
Input: A.Buchanan, 2020-10-25
Last update: A.Buchanan, 2020-11-03 more...
27 - P1381369
Andrew Buchanan
MatPlus.net Forum 28/10/2020
P1381369
(14+14) C+
KBP in 4.0
1. e3 a6 2. Lxa6 bxa6 3. De2 Lb7 4. Dxa6 Lxa6
play all play one stop play next play all
shortest PG with 4 units captured on 1 square
Henrik Juel: 1.Be2-e3 Ba7-a6 2.Lf1xa6 Bb7xa6 3.Dd1-e2 Lc8-b7 4.De2xa6 Lb7xa6
Very easy and C+ by Natch 3.1
Nice tempo move 3... Lb7 (2020-10-29)
A.Buchanan: Thanks - tempo is to force unique order on Wh moves (2020-10-30)
comment
Keywords: Unique Proof Game, Tempo Move, Task (Construction) (4), Superseded by (P1381879), x pieces capture on one square (4)
Genre: Retro
Computer test: C+ by Natch 3.1
FEN: rn1qkbnr/2pppppp/b7/8/8/4P3/PPPP1PPP/RNB1K1NR
Input: A.Buchanan, 2020-10-29
Last update: A.Buchanan, 2021-04-18 more...
28 - P1381879
Andrew Buchanan
MatPlus.net Forum 3/11/2020
P1381879
(13+13) C+
BP in 7.0
1. e4 a6 2. Lxa6 bxa6 3. De2 Lb7 4. Dxa6 Sxa6 5. b4 Db8 6. b5 Da7 7. bxa6 Dxa6
play all play one stop play next play all
Inspired by P1381620

See also P1381369
Henrik Juel: C+ Natch 3.1
1.Be2-e4 Ba7-a6 2.Lf1xa6 Bb7xa6 3.Dd1-e2 Lc8-b7
4.De2xa6 Sb8xa6 5.Bb2-b4 Dd8-b8 6.Bb4-b5 Db8-a7
7.Bb5xa6 Da7xa6
Six captures on a6 (2020-11-14)
comment
Keywords: Unique Proof Game, x pieces capture on one square (6), Construction task
Genre: Retro
Computer test: Natch 3.1
FEN: r3kbnr/1bpppppp/q7/8/4P3/8/P1PP1PPP/RNB1K1NR
Input: A.Buchanan, 2020-11-14
Last update: James Malcom, 2021-02-01 more...
29 - P1382432
Andrew Buchanan
Facebook 26/11/2020
P1382432
(11+15) C+
KBP
1. g4 h5 2. Lg2 hxg4 3. Lf3 gxf3 4. Kf1 fxe2+ 5. Kg2 exd1=T! 6. Kf3! Txc1 7. Ke2 Te1+ 8. Kxe1
play all play one stop play next play all
Henrik Juel: Excellent find, Andrew
Hint: length is 7.5 (2020-11-25)
A.Buchanan: Thanks Henrik - amazed to find it’s not in WinChloe or Yacpdb (2020-11-26)
A.Buchanan: The animation fails for "SPG", instead "KBP" is needed. (2020-11-26)
more ...
comment
Keywords: Unique Proof Game, Homebase (2), Pure Round Trip (K5), Ceriani-Frolkin Theme (t), Prentos Theme (t), Tempo Loss
Genre: Retro
Computer test: C+ Natch 3.1 C+ Euclide 1.01 for 6.0, 6.5, 7.0 & 7.5 moves, which is conclusive.
FEN: rnbqkbnr/ppppppp1/8/8/8/8/PPPP1P1P/RN2K1NR
Reprints: chess.stackexchange.com 26/11/2020
Input: A.Buchanan, 2020-11-25
Last update: A.Buchanan, 2020-11-26 more...
30 - P1382488
Andrew Buchanan
Thomas Thannheiser

1509 Julias Fairies 25/05/2020
P1382488
(13+15) C+
PG in 8.5
Alphabetic Chess
1. a4 a5 2. Ta3 Ta6 3. Tb3 Tb6 4. Sa3 Txb3 5. Sb5 Ta3 6. b4 Txa4 7. bxa5 Txa5 8. Sa3 Ta8 9. Sb1
play all play one stop play next play all
Aims to be the shortest SPG for a homebase position which demonstrates this fairy condition.
Henrik Juel: I cheated and used Jacobi
Nice condition-specific manouver by Sb1 (2020-11-26)
comment
Keywords: Unique Proof Game, Homebase (2), Alphabetic Chess, Economy record (Alphabetic homebase)
Genre: Retro, Fairies
Computer test: Jacobi v0.4.7
FEN: rnbqkbnr/1ppppppp/8/8/8/8/2PPPPPP/1NBQKBNR
Input: A.Buchanan, 2020-11-26
Last update: A.Buchanan, 2021-10-05 more...
31 - P1382808
Ronald Turnbull
Andrew Buchanan

PDB Website 20/01/2012
RT, correction AB
P1382808
(4+12)
h#3
AP
PRA
1. bxc3ep 0-0! (for AP reasons, not 1...Kf2?/Th2? etc) 2. Ta1 Txa1 3. Kc4 Txa4#
1. fxe3ep 0-0! (for AP reasons, not 1...Tf1?/Txh3? etc) b2 Txf3 3. Tc3 Tf4#
play all play one stop play next play all
For AP as for anything else, the default meta-convention is PRA before RS. Here we use AP to lock down wK & wTh1, so the last move was R: 1. c2-c4 or 1. e2-e4. There is a different h#3 in either case, beginning with ep and then 0-0.
Chessically corrects P1012059 following discussions. It's doubtful that AP logic works as simplistically described here, so this may still be unsound logically. Nevertheless, might as well fix the chess!
See P1399112, where the two parts each prove that one side of White castling rights remain. If this is correct, and only *one* part is required per castling, this implies that this Turnbull-Buchanan problem doesn’t work. For one part we have solution c_S and tries c_T1 & c_T2. In the other part, solution e_S and tries e_T1 & e_T2. Any of 5 combinations work:
c_S + e_S
c_S + e_T1
c_S + e_T2
c_T1 + e_S
c_T2 + e_S
because they all confirm that White retains castling rights.
Classify this problem as Golden Age because it’s on the wrong side of the evolving standard.
A.Buchanan: Let ??? Indicate respectively that w00, c ep & e ep are ok. Then YYN, YNY, NYN, NNY, NNN are the contenders.
Under PRA we reduce to YYN, YNY & NNN but the last has no solution so not the right paradigm.
Under SPRA with AP we reduce to YYN, YNY. Each considered as a separate part has kind of AP h#3, but I don’t understand how consolidation would take place over PRA anyway
Under RS with AP, we have 2 solutions assuming again that no consolidation. (2022-03-23)
comment
Keywords: a posteriori (AP) (Type Petrovic - cee), En passant as key (2), Castling (wk), Retro Strategy (RS), Golden Age (AP unconsolidated)
Genre: h#, Retro
Computer test: Forward logic sound by Popeye v4.85 However, seems that AP logic is not sound
FEN: 8/8/8/1nr1n3/ppPkPp2/rp1p1p1p/8/4K2R
Input: A.Buchanan, 2020-12-08
Last update: A.Buchanan, 2023-04-06 more...
32 - P1382819
Vladimir Korolkov
Andrew Buchanan

PDB Website 09/12/2020
VK, version AB
P1382819
(12+14) C+
h#3
1. 0-0 Tf1 2. Txf2 Txf2 3. Kh8 Tf8#
For parity reasons, not 1...0-0?
play all play one stop play next play all
Corrects (with a little more functionality) P0001361
Henrik Juel: How does one find the parity of the white moves, with DLSS missing? (2020-12-09)
Henrik Juel: Never mind
If White can castle, then last move was e2-e3, so we know where the missing white men were captured, and the parity is easily found (2020-12-09)
Henrik Juel: Suppose (for contradiction) that both sides may castle
Black has the move, so last move was e2-e3, and [Dd1,Lf1] were captured at home, and [Sb1,Sg1] were captured on e6,d5
The number of white and black moves in the game leading to the diagram are both even, so White should have the move
Conclusion: the castlings are mutually exclusive
In the solution Black must castle to get his king to h8, so White cannot get his Th1 to f1 by castling (2020-12-09)
comment
Keywords: Parity Argument, Castling (wksk), Castling, mutual exclusive
Genre: h#, Retro
Computer test: C+ Popeye v4.85 + thinking
FEN: 2b1k2r/rpppp1pp/p2n4/3p4/8/4P3/PPPP1PPP/RnB1K2R
Input: A.Buchanan, 2020-12-09
Last update: A.Buchanan, 2020-12-09 more...
33 - P1382844
Hans Gruber
Andrew Buchanan

PDB Website 11/12/2020
HG, version AB
P1382844
(6+6) C+
h=4
1. d1=D g7 2. Dd5 g8=S 3. Db7+ axb7 4. a1=L bxc8=T = patt
play all play one stop play next play all
corrected version of P1013759, agreed with composer
Henrik Juel: 1.d1=D g7 2.Dd5 g8=S 3.Db7+ axb7 4.a1=L bxc8=T =
Nice version with just Pe4 as a technical unit preventing cooks (2020-12-10)
comment
Keywords: Allumwandlung
Genre: Fairies
Computer test: C+ Popeye v4.85
FEN: 1Kn5/3k4/P3p1P1/4P3/4P3/8/pp1p4/1N6
Input: A.Buchanan, 2020-12-10
Last update: A.Buchanan, 2021-07-05 more...
34 - P1382870
Andrew Buchanan
1 The Problemist Supplement 169, p. 120, 11/2020
P1382870
(1+4) C+
h#6.5
Illegal position
1. ... f4 2. Sf6 f5 3. Sh5 f6 4. Sg7 fxg7 5. Kd8! g8=D+ 6. Kd7 Dg4+ 7. Ke8 Dc8#
play all play one stop play next play all
A.Buchanan: These are not part of the TPS solving competition: the solutions are given in the same issue. But the automatic PDB problem blocker stops them from being commented on. As a work-around for now, I have set the year to 1020 (famous of course as the year Byzantine troops under Catepan Basil Boioannes (supported by his ally Prince Pandulf IV) captured the fortress of Troia). (2020-12-12)
Henrik Juel: Thanks for the enlightenment, Andrew, and for the history lesson
Solution
1... f4 2.Sf6 f5 3.Sh5 f6 4.Sg7 fxg7 5.Kd8! g8=D+ 6.Kd7 Dg4+ 7.Ke8 Dc8# (2020-12-12)
Henrik Juel: Adding wKe1 for legality while maintaining homebase causes many cooks, e.g.
1...f2-f4 2.e7-e5 f4*e5 3.Ke8-e7 e5-e6 4.Ke7-f6 e6*f7 5.Kf6-f5 Ke1-f2 6.Kf5-g4 f7*g8=Q+ 7.Kg4-h3 Qg8-g3# (2020-12-12)
A.Buchanan: Yes wK is just too dominant in these longer h#. But homebase is awesome constraint on design. There are some tremendous h# already, and much of their impact is because of homebase. (2020-12-12)
Olaf Jenkner: Now I see, homebase was the theme... (2020-12-12)
Olaf Jenkner: The king could easily stand at a1 without impact of correctness. (2020-12-12)
A.Buchanan: Yes thematic (2020-12-12)
more ...
comment
Keywords: Illegal position (no wK), Homebase (2), Minimal (super)
Genre: h#
Computer test: C+ Popeye 4.61
FEN: 4k1n1/4pp2/8/8/8/8/5P2/8
Input: A.Buchanan, 2020-12-11
Last update: A.Buchanan, 2023-12-11 more...
35 - P1382871
Andrew Buchanan
Geoff Foster

2 The Problemist Supplement 169, p. 120, 11/2020
P1382871
(1+4) C+
h#7
Illegal position
1. Sc6 e4 2. Sd8! e5 3. Sf7 e6 4. Kd8 exf7 5. Kc8! f8=D+ 6. Kc7 Df4+ 7. Kd8 Db8#
play all play one stop play next play all
more ...
comment
Keywords: Homebase (2), Illegal position (no wK), Minimal (super), Excelsior
Genre: h#
Computer test: C+ Popeye 4.61
FEN: 1n2k3/3pp3/8/8/8/8/4P3/8
Reprints: chess.stackexchange.com 27/05/2023
MatPlus.net Forum 28/05/2023
Input: A.Buchanan, 2020-12-11
Last update: A.Buchanan, 2023-12-11 more...
36 - P1382872
Andrew Buchanan
3 The Problemist Supplement 169, p. 120, 11/2020
P1382872
(2+3) C+
h#7
Illegal position
1. c5 Sd2 2. c4 Sb3 3. cxb3 c4 4. b2 c5 5. b1=T c6 6. Te1 (not 6.Tb7?) c7 7. Te7 c8=D#
play all play one stop play next play all
Out of about 90 examples, this is the only orthodox homebase h# with a rook sub-promotion.
more ...
comment
Keywords: Homebase (2), Illegal position (no wK)
Genre: h#
Computer test: C+ Popeye 4.61
FEN: 4k3/2p2p2/8/8/8/8/2P5/1N6
Input: A.Buchanan, 2020-12-11
Last update: A.Buchanan, 2023-12-11 more...
37 - P1382873
Andrew Buchanan
4 The Problemist Supplement 169, p. 120, 11/2020
P1382873
(1+5) C+
h#8
Illegal position
1. Lh3 gxh3 2. g5 h4 3. g4 h5 4. g3 h6 5. g2 h7 6. g1=D h8=D+ 7. Dg8 Dh3 8. Df7 Dc8#
play all play one stop play next play all
Henrik Juel: C+ Popeye 4.61
This one is my favorite in the series
Why not add white king somewhere to make the position legal? (2020-12-11)
A.Buchanan: Thanks Henrik. There are now about 100 homebase h# compositions in PDB, following an article I wrote in TPS a couple of years ago, and the legal length limit seems to be about 6.0 moves. Since wK is very good at enabling cooks beyond that point, it's interesting and funny to see what happens if he is removed. The homebase criterion however is paramount, so I absolutely can't just stick wK somewhere else. If I remember properly, Geoff did find out-of-the-way places to stick wK for the other three compositions, but not for this one. As a retro enthusiast, obviously I love the fractal landscape of legal positions, but by the same token, I see nothing wrong with thematic illegality: illegality never prevents one from playing forwards if one is calm about it. And it opens the door to an otherwise inaccessible region of design space, with novel king-free mating patterns. Can anyone push the length further, or find any homebase h# with a bishop promotion? (2020-12-12)
Henrik Juel: Now I understand what is going on
I do not care much about Codex issues, but for some reason I dislike illegal positions for regular problems
Possibly this should be categorized as a fairy problem
Solution
1. Lh3 gxh3 2. g5 h4 3. g4 h5 4. g3 h6 5. g2 h7 6. g1=D h8=D+ 7. Dg8 Dh3 8. Df7 Dc8# (2020-12-12)
A.Buchanan: Thanks for you perspective, Henrik.
Surely some might consider white king as a fairy condition. As you implicitly point out while the *effect* is no white king, there can be multiple *justifications*, just one of which is the direct fairy condition (nowk). As a composer, I chose a different explanation: illegal position. These positions are exactly as illegal as a position with wPb1 & wBa1. In both situations, we can prove there is no sequence of legal moves from the initial game array (PAS). And in both situations we can simply play forward chess, with no issue. Obviously I love retrograde analysis, which has the fractal landscape of legal positions as its bedrock. But it's nice to look at the other side sometimes, and I find it odd that some other people are nervous about doing that.
The distinction between justification and effect wasn't clear to me until recently. Other examples are Bosma & Dummy Pawn. An instance of either may be a joke or a fairy problem. Dummy pawn might also be due to illegal position, or it might be a historical problem, or a contemporary problem set in a previous historical period (which would not make it fairy, it would just have an invalid timestamp).
You may consider threats and set play 20 times a day, but never worry about the legality of the positions in which those moves are playable. And that's because the laws extend smoothly to such illegal positions (except for certain corner cases, and even those can be worked out with a little trying). But even if you found that a threat was in a position from which White couldn't actually have the move, you wouldn't care. So in this area you accept illegality. Orthodox problems couldn't exist without the principle that the laws work happily in illegal positions. It's like mathematics & complex numbers.
The Codex is surprisingly astute about illegality. An illegal position does not prevent soundness: the only stated downside is it *might* not be acceptable to a tourney. The Codex also says that illegal and fairy positions do not normally support retrograde analysis. Although, these days fairy retro analysis exists. The implication in any case is that from the fairy position, illegality and fairy concepts are distinct.
For me, the position is just a node in a graph which happens to be inaccessible from the start node. It's horribly inefficient to have to invoke a specific fairy condition out of so many. Much cleaner and more satisfying to say, well we are in that inaccessible node, so let's play chess. (2020-12-12)
comment
Keywords: Homebase (2), Illegal position (no wK), Minimal (super)
Genre: h#
Computer test: C+ Popeye 4.61
FEN: 2b1k3/2p1p1p1/8/8/8/8/6P1/8
Input: A.Buchanan, 2020-12-11
Last update: A.Buchanan, 2023-12-11 more...
38 - P1382903
Andrey Frolkin
Andrew Buchanan

2 Die Schwalbe 360-1, p. 737, 12/2020
P1382903
(14+12)
Erster Zug des wTf6?
R: 1. Tf1xBf6! b6xSa5 2. 0-0! a7xSb6 3. Lf1-e2 Kd4-e5,Kf4-e5 4. e2-e3+
play all play one stop play next play all
James Malcom: How does this work exactly? What forbids the rook from just making some random tempi move in a game that leads to this position? (2020-12-12)
Mario Richter: James, think of time pressure. In the diagram, Black has only two retractions (a7xSb6xSa5). The only way to unlock the position is the retraction of e2-e3.
Little hint: castling is considered as a king m,opve ... (2020-12-12)
Henrik Juel: By now there are so many clues revealed for this fine retro that I dare to give a retroplay despite the Byzantine dating, in this case indicating an ongoing solving competition
R: 1.Tf1xPf6 b6xSa5 2.0-0 a7xSb6 3.Lf1-e2 Kd4,Kf4 4.e2-e3+ etc.
Incidentally, TxP is not the first move, but the last... (2020-12-12)
Henrik Juel: I missed the from square in the retraction by the black king, sorry
3... Kd4-e5,Kf4-e5 (2020-12-12)
A.Buchanan: Ha, there is no solving competition for these either. But it's to avoid Gerd's solving competition protection algorithm picking up false positives (2020-12-12)
A.Buchanan: TxP happens to be the last move, but it's also the first effective move of the rook, as it is considered to be a *passenger* in the castling, and not to have moved yet. Otherwise can't get first move of a rook fixed if it capturing (except possibly by DP logic). See the explanatory article: https://www.dieschwalbe.de/download/artikel/Passenger_Rooks.pdf (2020-12-12)
A.Buchanan: Your solution is completely correct, Henrik! (2020-12-12)
comment
Keywords: Economy record (First move), Type A, First Move? (TxB), Castling in the retro play (wk), Non-standard material (l), Castling (wk)
Genre: Retro
FEN: 5b1n/1p2prBP/P2PrRQb/p2pk1pR/7p/3PP3/1P2B1PP/6K1
Reprints: 2 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
39 - P1382904
Andrey Frolkin
Andrew Buchanan

3 Die Schwalbe 360-1, p. 737, 12/2020
P1382904
(14+10)
Erster Zug des wTf6?
R: 1. Lg2-f3 b4-b3 2. Tf1xSf6! b5-b4 3. 0-0! b6-b5 4. Lf1-g2 Kf4-g5,Kh4-g5 5. g2-g3+
play all play one stop play next play all
Henrik Juel: Oh, I was confused by the LLLLl, which should be TLLLLl, I believe
R: 1.Lg2-f3 b4-b3 2.Tf1xSf6! b5-b4 3.0-0 b6-b5 4.Lf1-g2 Kf4-g5,Kh4-g5 5.g2-g3+ (2020-12-12)
A.Buchanan: Thanks for the catch. I copied the diagrams straight from the article FEN, so should be clean of transcription errors, but then I put in the non-standard material field by hand & eye, so could be other errors as here. (2020-12-12)
A.Buchanan: Your move sequence is again correct! :D (2020-12-12)
more ...
comment
Keywords: Economy record (First move), Type A, First Move? (TxS), Castling in the retro play (wk), Non-standard material (TLLLLl), Castling (wk)
Genre: Retro
FEN: 3bRBB1/2ppBQRp/3ppRBb/6kB/6p1/1p3BP1/4P2P/6K1
Reprints: 3 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
40 - P1382906
Andrey Frolkin
Andrew Buchanan

4 Die Schwalbe 360-1, p. 738, 12/2020
P1382906
(14+9)
Erster Zug des wTf8?
R: 1. Tf1xLf8! e4-e3 2. 0-0! e5-e4 3. Lf1-g2 e6-e5 4. g2xBh3 h4-h3 and e.g. 5. d4-d5 h5-h4 6. Le4-c6 h6-h5 7. c7-c8=L! h7-h6 8. c6-c7 c7xLb6
play all play one stop play next play all
Henrik Juel: Good motivation for TxL
R: 1.Tf1xLf8! e4-e3 2.0-0 e5-e4 3.Lf1-g2 e6-e5 4.g2xPh3 h4-h3 and e.g.
5.d4-d5 h5-h4 6.Le4-c6 h6-h5 7.c7-c8=L! h7-h6 8.c6-c7 c7xLb6
f7xTg8=L happened early (2020-12-12)
comment
Keywords: Economy record (First move), Type A, First Move? (TxL), Castling in the retro play (wk), Non-standard material (LL), Castling (wk)
Genre: Retro
FEN: k1B2RQ1/Pp1pp1p1/rpB3N1/pN1P4/8/4p2P/2P1P1BP/6K1
Reprints: 4 Die Schwalbe Online 12/2020
www.thbrand.de 13/12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
41 - P1382907
Andrey Frolkin
Andrew Buchanan

5 Die Schwalbe 360-1, p. 738, 12/2020
P1382907
(13+12)
Erster Zug des wTf6?
R: 1. Tf1xTf6 c3-c2 2. Lf3-a8 c4-c3 3. 0-0 c5-c4 4. Lg2-f3 c6-c5 5. Lf1-g2 Kf4-g5,Kh4-g5 6. g2-g3+
play all play one stop play next play all
Hans-Jürgen Manthey: 1. Lg2-a8 c3-c2 2. Tf1xTf6 c4-c3 3. O-O ??? (Rochade nicht möglich wegen sTf6 !)

mögliche Lösung:
1. Tf1xTf6 c3-c2 2. Lf3-a8 c4-c3 3. O-O c5-c4 4. Lg2-f3 c6-c5 5. Lf1-g2 Kf4-g5 6. g2-g3+ Sg5-h7 7. Ld3-g6 Se4-g5 8. Th7-g7 Dg6-f7 9. f7-f8L Tf5-f6 10. Le5-h8 Lf8-h6 11. Lh4-e7 Dg5-g6 12. La7-e5 Tf6-f5 13. Lb8-a7 Th6-f6 14. Lf6-d8 Sc5-e4 15. Lb2-f6 Dd8-g5 16. Lf2-h4 Kg5-f4 17. f6-f7 Sa6-c5 18. Te7-h7 Th8-h6 19. f5-f6 Kh6-g5 20. La3-b2 Kg7-h6 21. Lf7-e8+ Kf6-g7 22. Lc1-a3 Kg7-f6 23. b7-b8L h7-h5 24. La7-f2 Kf6-g7 25. Lb8-a7 Kg7-f6 26. b6-b7 Kf6-g7 27. b7-b8L Kg7-f6 28. Te8-e7 Df6-d8 29. Ta8-e8 g5-g4 30. Le8-f7 f7xSe6 31. Sf4-e6+ Sb8-a6 32. Ta1-a8 Dd8-f6 33. e7-e8L Kf6-g7 34. e6-e7 Ke7-f6 35. b5-b6 g6-g5 36. b6-b7 g7-g6 37. c4xLb5 La6-b5 38. c2-c4 Lc8-a6 39. La6-d3 Ke8-e7 40. Lb7-a6 Ke7-e8 41. La8-b7 Ke8-e7 42. a7-a8L Ke7-e8 43. d5xTe6 Te3-e6 44. a6-a7 Ke8-e7 45. a5-a6 Ke7-e8 46. a4-a5 Ke8-e7 47. a2-a4 Ta3-e3 48. Sh3-f4 Ta8-a3 49. Sg1-h3 b7xSc6 50. Sa7-c6 Sc6-b8 51. Sb5xa7 e7xDd6 52. Dh6-d6 Sb8-c6 53. Dd2-h6 Sc6-b8 54. Dd1-d2 Sb8-c6 55. f4-f5 Sc6-b8 56. f2-f4 Sb8-c6 57. d4-d5 Sc6-b8 58. d2-d4 Sb8-c6 59. Sc3-b5 Sc6-b8 60. Sb1-c3 Sb8-c6 61. b5-b6 Sc6-b8 62. b4-b5 Sb8-c6 63. b2-b4 (2020-12-14)
more ...
comment
Keywords: Economy record (First move), Type A, First Move? (TxT), Castling in the retro play (wk), Non-standard material (LLLLL), Castling (wk)
Genre: Retro
FEN: B2BBBnB/2ppBqRn/3ppRBb/6kp/6p1/6P1/2p1P2P/6K1
Reprints: 5 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
42 - P1382908
Andrey Frolkin
Andrew Buchanan

6 Die Schwalbe 360-1, p. 738, 12/2020
P1382908
(11+14)
Erster Zug des wTf6?
R: 1. Tf1xDf6 b3xLc2 2. Le4-c2 and e.g. 2. ... c5-c4 3. Lf3-e4 c6-c5 4. 0-0 b4-b3 5. Lg2-f3 b5-b4 6. Lf1-g2 Kf4-g5 7. g2-g3+
play all play one stop play next play all
more ...
comment
Keywords: Economy record (First move), Type A, First Move? (TxD), Castling in the retro play (wk), Non-standard material (L), Castling (wk)
Genre: Retro
FEN: 3BBn2/2pRBrPn/3pQRrb/3pp1kp/2p3p1/6P1/2p1P2P/6K1
Reprints: 6 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
43 - P1382909
Andrey Frolkin
Andrew Buchanan

7 Die Schwalbe 360-1, p. 740, 12/2020
after Schwarzkopf, Dittmann & Murkisch
P1382909
(10+1)
Erster Zug des wTg1?
See P0007812.
Typo in published version, stip given incorrectly as "Last move?"
Henrik Juel: Last move was e2xDTLSPd3+
The top four pawns seem unnecessary (2020-12-12)
Henrik Juel: Sorry, the pawns are necessary to rule out Th1xg1 as first move (2020-12-12)
comment
Keywords: Economy record (First move), Type C, First Move? (T-)
Genre: Retro
FEN: 8/8/5PPP/8/2k4P/3P4/2K3PP/5BR1
Reprints: 7 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2021-05-08 more...
44 - P1382910
Andrey Frolkin
Andrew Buchanan

8 Die Schwalbe 360-1, p. 740, 12/2020
P1382910
(16+6)
Erster Zug des wTf3?
R: 1. Tf1xBf3+! f4-f3 2. f3xBe4+ e5-e4 3. 0-0! Kg2-g3
play all play one stop play next play all
Henrik Juel: White captured TxPf3+, axbxcxd, bxcxd, cxd, fxPe, g5xh6, and h6xg7-g8=L
R: 1.Tf1xPf3+ f4-f3 2,f3xPe4+ e5-e4 3.0-0 Kg2-g3 (2020-12-12)
comment
Keywords: Economy record (First move), Type C, First Move? (TxB), Castling in the retro play (wk), Non-standard material (DTLL), Castling (wk)
Genre: Retro
FEN: 3N4/ppp4P/4NBpB/5BQp/4P1BR/R3QRk1/3PP3/6K1
Reprints: 8 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
45 - P1382911
Andrey Frolkin
Andrew Buchanan

9 Die Schwalbe 360-1, p. 740, 12/2020
P1382911
(12+6)
Erster Zug des wTd1?
R: 1. Tf1xSd1+! Sc3-d1 2. 0-0+!
play all play one stop play next play all
Henrik Juel: Black has played c3/a3xLb2-b1=T, earlier Kb4-a3-b2-b1, and still earlier Sb3xTa1
R: 1.Tf1xSd1+ Sc3-d1 2.0-0+ (2020-12-12)
Henrik Juel: A very impressive set of retros
Thanks for making them available, Andrew (2020-12-12)
A.Buchanan: Very welcome Henrik: thanks for your invaluable solving! (2020-12-13)
comment
Keywords: Economy record (First move), Type C, First Move? (TxS), Castling in the retro play (wk), Castling (wk)
Genre: Retro
FEN: N7/p1p5/8/8/8/PP6/qrPPPPPP/nNkR2K1
Reprints: 9 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
46 - P1382912
Andrey Frolkin
Andrew Buchanan

10 Die Schwalbe 360-1, p. 741, 12/2020
P1382912
(10+8)
Erster Zug des wTf8?
R: 1. Tf1xLf8+ & e.g. f4xSg3,f4x~g3 2. 0-0 e5xLf4,e5x~f4 3. Lf1-g2 d6xDe5,d6x~e5 4. g2xSh3,g2x~h3
and later White unpromotes via a7,c7&f7
play all play one stop play next play all
more ...
comment
Keywords: Economy record (First move), Type C, First Move? (TxL), Castling in the retro play (wk), Castling (wk)
Genre: Retro
FEN: R4R1k/1p1pp1pP/6pp/3N4/8/6pP/4P1BP/3B2K1
Reprints: 10 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
47 - P1382913
Andrey Frolkin
Andrew Buchanan

11 Die Schwalbe 360-1, p. 741, 12/2020
P1382913
(13+8)
First move of [wTh1]?
R: 1. ... g3xTf2+! 2. Tf1xTf2+! Tf3xTf2 (not 2.Tf1xSf2+?Sh1xTf2? because the second wT delivers illegal check) 3. 0-0! Dh2-h3 and e.g. 4. Tf1-f2 Lg1-e3 5. Sf2-d1 Ke5-f4 6. e3xBd4+
play all play one stop play next play all
Henrik Juel: R: 1... g3xTf2 2.Tf1xTf2 Tf3xTf2 3.0-0 Dh2-h3 and e.g.
4.Tf1-f2 Lg1-e3 5.Sf2-d1 Ke5-f4 6.e3xPd4+
The remaining capture by Black was f5xLg4
[Pa7] was captured by a white officer (2020-12-13)
comment
Keywords: Economy record (First move), Type C, First Move? (TxT), Castling in the retro play (wk), Castling (wk)
Genre: Retro
FEN: 8/1p5p/8/5PP1/3PNkpB/2PPb2q/P1pPPpQ1/3N2K1
Reprints: 11 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
48 - P1382914
Andrey Frolkin
Andrew Buchanan

12c Die Schwalbe 360-1, p. 741, 12/2020
P1382914
(16+8)
Erster Zug des wTf2?
R: 1. Tf1xDf2+ Dg3-f2+ 2. Lf2xBb6 b7-b6 3. 0-0! Dh2-g3
play all play one stop play next play all
Minor correction: sBd7->c6 wSb2->wL
Henrik Juel: Not R: 1.Tf1xDf2+ Dg3-f2+ 2.Lf2xPb6 b7-b6 3.0-0 Dh2-g3,
because White can no longer uncapture hxgxh
What was the intention? (2020-12-13)
A.Buchanan: Attempted repair to avoid accidentally retro-blocking c8 (2020-12-23)
Hans-Jürgen Manthey: mögliches Retrospiel: 1. Tf1xDf2# Dg3-f2 2. Lf2xb6+ b7-b6 3. O-O Dh2-g3 4. Se3-g2 Dg2-h2 5. Sc4-e3 Dh2-g2 6. Tg1-g4 Dg2-h2 7. Sa3-c4 Dh2-g2 8. g4-g5 Dg2-h2 9. Lb6-f2 Dh2-g2 10. Ld8-b6 Ke3-f3 11. d7-d8L Kd4-e3 12. Sc3-e2+ Kc5-d4 13. Le2-d1 Kd6-c5 14. Lf1-e2 Tf2-d2 15. Tg2-g1 Tf3-f2 16. Td2-g2 Se2-c1 17. Td1-d2 Te3-f3 18. Tb1-d1 Te6-e3 19. Lc1-b2 Th6-e6 20. f2-f4 Th8-h6 21. g2-g4 Sf4-e2 22. Se2-f3 Sd5-f4 23. Sg1-e2 Ke6-d6 24. Df4-h4 Ta8-h8 25. Da4xBf4 f5-f4 26. Da5-a4 Db8-h2 27. g4xTh5 h4-h3 28. b2-b3 Sb3-a1 29. Dd8xBa5 Sc5-b3 30. Df8-d8 a7-a5 31. Dh8xLf8 f7-f5 32. d6-d7 Kd7-e6 33. e5xBd6 Sf6-d5 34. Dh7-h8 Ke8-d7 35. De4-h7 Sg8-f6 36. Ta1-b1 Dd8-b8 37. Sb1-a3 Th8-h5 38. h3xLg4 h5-h4 39. h2-h3 Lc8-g4 40. De2-e4 h7-h5 41. e4-e5 c7-c6 42. d2-d3 Sa6-c5 43. Dd1-e2 d7-d6 46. e3-e4 Sb8-a6 47. e2-e3 (2020-12-25)
more ...
comment
Keywords: Economy record (First move), Type C, First Move? (TxD), Castling in the retro play (wk), Non-standard material (S), Castling (wk)
Genre: Retro
FEN: 8/4p1p1/1Bp5/6PP/5PRQ/1P1P1k1p/PBPrNRN1/n1nB2K1
Reprints: 12 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
49 - P1382915
Andrey Frolkin
Andrew Buchanan

13 Die Schwalbe 360-1, p. 741, 12/2020
P1382915
(15+10)
Erster Zug des wTf3?
R: 1. Tf1xDf3+! Sf2-h1 2. 0-0! Se4-f2 and e.g. 3. Sf2-h3 Lh3-g4 4. Lg4-h5 Th5-g5 5. g5-g6 Th6-h5 6. Lh5-g4
play all play one stop play next play all
more ...
comment
Keywords: First Move? (TxD), Type C, Castling in the retro play (wk), Non-standard material (t), Castling (wk)
Genre: Retro
FEN: 8/4p2p/6P1/5PrB/5pbb/1PPPkRRN/1PPr2Pr/2BQ2Kn
Reprints: 13 Die Schwalbe Online 12/2020
Input: A.Buchanan, 2020-12-12
Last update: A.Buchanan, 2023-08-15 more...
50 - P1383249
Markus Johannes Ott
Andrew Buchanan

0 Die Schwalbe Online 12/2020
P1383249
(12+1)
Erster Zug des wBa3?
R: 1. b2xTa3 Tb3-a3,Tb3xSa3,Tb3xLa3
play all play one stop play next play all
Henrik Juel: White pawns captured all 15 missing black men, so last move was not, say, Kxc2
Last move was b2xTa3 allowing Tb3-a3 or Tb3xLSa3 as preceding move
So first move by Pa3 was just this: b2xTa3 (2020-12-23)
comment
Keywords: First Move? (BxT), Type A, Economy record (First move)
Genre: Retro
FEN: 8/1P6/2P5/PP1B4/kBP5/P2N4/P1K5/1N6
Input: A.Buchanan, 2020-12-23
Last update: A.Buchanan, 2020-12-26 more...
51 - P1384899
Andrew Buchanan
Facebook 03/01/2021
motto = "God save the queen!"
P1384899
(2+3) C+
h#3.5
1. ... Lc8 2. Ke8 Kf5 3. Df8+ Ke6 4. Ld8 Ld7#
play all play one stop play next play all
After I posted the meme https://knowyourmeme.com/photos/1459595-queen-elizabeth-chess-moves in Chess Studies and Composition group in Facebook, I was asked to augment it with a composition. So I added three pieces, but kept the spatial relationship between Her Majesty and some (arch)bishop I don't recognize. However an earlier version https://knowyourmeme.com/photos/1459589-queen-elizabeth-chess-moves shows that someone j'adoubed the board! (It's probably treason to j'adoube the queen herself.)
Henrik Juel: C+ Popeye 4.61 (2021-01-03)
comment
Keywords: Aristocrat, Minimal (L), Miniature, Ideal mate, Parody (QE2)
Genre: h#
Computer test: C+ Popeye 4.61
FEN: 8/4k3/3q4/5Bb1/4K3/8/8/8
Input: A.Buchanan, 2021-01-03
Last update: A.Buchanan, 2022-01-31 more...
52 - P1385595
Andrew Buchanan
James Malcom
Hauke Reddmann
Michel Caillaud

MatPlus.net Forum 06/01/2021
in memory of Conrad Staugaard
P1385595
(14+13)
PG in 10.0
Staugaard castling
b) 1. d4 f5 2. Kd2 f4 3. Kd3 f3 4. Ke4 fxe2 5. Kf5 e1=T 6. De2 g5 7. Dxe7+ Sxe7+ 8. Kf6 Lg7+ 9. Kxg7 Sd5 10. Kxh8 0-0-0-0-0-0#
play all play one stop play next play all
Objective: Staugaard (Pam-Krabbé) castling as mating move.
Henrik Juel: solution
1. Bd2-d4 Bf7-f5 2. Ke1-d2 Bf5-f4 3. Kd2-d3 Bf4-f3
4. Kd3-e4 Bf3xe2 5. Ke4-f5 Be2-e1=T 6. Dd1-e2 Bg7-g5
7. De2xe7 Sg8xe7 8. Kf5-f6 Lf8-g7 9. Kf6xg7 Se7-d5
10. Kg7xh8 0-0-0-0-0-0#
First 9.5 moves are C+ Euclide 1.01
On behalf of the danish inventor of the looong castling, I thank for the dedication (2021-01-21)
James Malcom: After the 12.5 Andrew and I made, this turns out the fastest possible. 9.0 if you go non-unique. (2021-01-21)
A.Buchanan: Welcome, Henrik. Any idea what his initial "C." stands for? I couldn't find it online. (2021-01-22)
Henrik Juel: Unfortunately not, Andrew
In those days the first name was almost always abbreviated to an initial
Christian was a very common first name, but this was usually abbreviated to Chr.
So a wild guess is Carl, but it really could be anything starting with C
In a Skakbladet issue he is referred to as Direktør Staugaard, but this just means that he was in charge of a company (2021-01-22)
A.Buchanan: I have posted an English definition of the keyword. Please check if it suits. (2021-01-22)
Henrik Juel: Searching for direktør staugaard, randers (a danish city) yields
Conrad Staugaard (1852-1922)
so this is my best bet
Conrad Staugaard headed a bank in Randers, founded by him in 1891, but the CV in
http://historiskranders.dk/randers-biografier/
does not mention anything about playing chess or chess problems
Chess playing was very common in the middle class, so the biographer may not have found it worth mentioning (2021-01-22)
Henrik Juel: Your keyword definition seems fine,
except for the spelling of showcase... (2021-01-22)
A.Buchanan: Haha bingo: "Staugaard was a well-known and excellent chess-player, one of the many traits he had in common with Lewis Carroll". MMA SAM - Tidsskrift.dk. Googling for "Conrad Staugaard skak" brings up the pdf for Rama Sama. Please tell us what you make of it, Henrik :) In the mean time, I have updated the author info for him (2021-01-22)
Henrik Juel: Very good, Andrew
Ah, the joys of Google...
In the danish text there is not only your citation on chess, but also one on chess problems
There are also examples of Conrad's excentric behaviour, in line with him inventing the looong castling
That C. Staugaard might be Conrad's younger brother Carl (who surely also knew about chess) is ruled out by the fact that Carl emigrated to South America in 1901, because he experienced disappointments in his love live... (2021-01-22)
A.Buchanan: Yes it said he had lots of amazing concepts. The idea about the banner for his nursemaid to take his children for walks without getting her arms stretched is very funny. This is our man. He also seems to have been a good man, and an effective businessman. And loved enough by his friends for a 120 page book to have been commissioned in his memory. He is reminiscent of other children’s authors like Edward Lear, Dr Seuss, Heinrich Hoffmann... I’m so happy that this problem has brought him back to our awareness (2021-01-23)
comment
Keywords: Unique Proof Game, Staugaard castling, Prenix (t), Promotion (t), Castling as mating move, Economy record
Genre: Retro, Fairies
Computer test: HC+ the last move can only have been 0^6 discovering mate & the first 9.5 moves are C+ Euclide 1.01.
FEN: rnbq3K/ppppr2p/4k3/3n2p1/3P4/8/PPP2PPP/RNB2BNR
Input: A.Buchanan, 2021-01-21
Last update: Rainer Staudte, 2021-05-10 more...
53 - P1385597
Andrew Buchanan
MatPlus.net Forum 08/01/2021
P1385597
(14+14) C+
PG in 7.5
Staugaard castling
b) 1. e4 d5 2. Ld3 Lf5 3. exf5 Dd6 4. f6 Sd7 5. Lg6 0-0-0 6. fxe7 Dxh2 7. e8=T Dxh1 8. 0-0-0-0-0-0
play all play one stop play next play all
Popeye says there's no orthodox solution in 7.5, so it must be Staugaard. With castling as W8, there Popeye finds a unique solution for the first 7.0. Otherwise we can count both sides' moves, with e2-e4xLf5-f6xBe7-e8=T. If we R: 1. Ld3-g6 Dh7xTh8 2. 0^6, then Popeye says no solution, and there is no alternative White retraction. This is enough for me to say HC+.
Objective: Staugaard (Pam-Krabbé) + queenside castling.
more ...
comment
Keywords: Unique Proof Game, Staugaard castling, Castling (2), Prenix (T), Promotion (T)
Genre: Retro, Fairies
Computer test: HC+ Popeye v4.85 + argument in sol text
FEN: 2kr1bnr/pppn1ppp/6B1/3p4/8/4K3/PPPPRPP1/RNBQ2Nq
Input: A.Buchanan, 2021-01-21
Last update: Rainer Staudte, 2021-05-10 more...
54 - P1385598
Andrew Buchanan
MatPlus.net Forum 10/01/2021
P1385598
(14+14)
PG in 7.5
Staugaard castling
1. d4 e5 2. Lf4 exf4 3. Dd3 f3 4. Dxh7 fxe2 5. f4 g6 6. Kf2 e1=T 7. Dxh8 0-0-0-0-0-0 8. De5#
play all play one stop play next play all
Objective: Staugaard (Pam-Krabbé) king is mated.
Henrik Juel: The first 6.5 moves are C+ Euclide 1.01 (2021-05-08)
A.Buchanan: Thanks Henrik. In the advance of an engine supporting Staugaard, here is my purely HC+ proof of soundness. No orthodox solution so 6 Bl moves needed to Staugaard. Other Bl move was g7-g6 or h7xg6. bRh8 & other bPg/bPh never moved - captured by Wh raider(s). Only piece that could have captured wPe was bPe, so it captured twice, other prey being wB, which thus moved once, and could not have been the raider. 6 Wh moves now countable without raiding, so wQ raided, and took 4 moves. All Wh moves now accounted for, so bPe7-e5xf4-f3xe2-e1=T. wQ could only have exited on d file, as diagonal d1-h5 open too late. Thus wQ-d3xh7xh8-e5#. All moves are known, and jigsaw of them moves is unique, ensuring each side can always move. (2021-05-08)
A.Buchanan: I forgot to say that I think my manual proof, while watertight, is too complex to make the status of this problem HC+. I think HC+ is for where the H part is self-evident. (2021-05-08)
more ...
comment
Keywords: Unique Proof Game, Staugaard castling, Prenix (t), Promotion (t), Castling
Genre: Retro, Fairies
FEN: rnbq1bn1/pppprp2/4k1p1/4Q3/3P4/5P2/PPP2KPP/RN3BNR
Input: A.Buchanan, 2021-01-21
Last update: Rainer Staudte, 2021-05-10 more...
55 - P1385601
Andrew Buchanan
MatPlus.net Forum 16/01/2021
to Joost de Heer
P1385601
(12+15)
PG in 11.5
b) Is the position before the last black move a sound proof game in 10.5?
Staugaard castling
a) 1. e3 h6 2. Ld3 Th7 3. Lxh7 e6 4. Lf5 exf5 5. Sf3 f4 6. 0-0 fxe3 7. Se1 exd2 8. Df3 dxe1=T 9. Le3 b6 10. Sd2 b5 11. Lb6 0-0-0-0-0-0 12. Tfb1
b) No: 1. e3 h6 2. Ld3 Th7 3. Lxh7 e6 4. Lf5 exf5 5. Sf3 f4 6. 0-0 fxe3 7. Se1 exd2 8. Df3 and now d1=T 9. Le3 Txe1/b5/b5 10. Sd2/Sd2/Lb6 b5/Txe1/Txe1 11. Lb6/Lb6/Sd2 have no P-K castling rights.
play all play one stop play next play all
Objective: Play of Staugaard (Pam-Krabbé) castling makes unsound PG sound.
Henrik Juel: I see no castling paradox (2021-01-21)
A.Buchanan: I must complete the stipulation, sry (2021-01-22)
A.Buchanan: Not really paradox in the usual hidden/fake sense. Need a different term for the occasional idea that an earlier point in the proof game is not unique. (2021-01-22)
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comment
Keywords: Unique Proof Game, Staugaard castling, Phoenix (t), Promotion (t), Castling (2)
Genre: Retro, Fairies
FEN: rnbq1bn1/p1pprpp1/1B2k2p/1p6/8/5Q2/PPPN1PPP/RR4K1
Input: A.Buchanan, 2021-01-21
Last update: A.Buchanan, 2021-05-09 more...
56 - P1386033
Andrew Buchanan
chess.stackexchange.com 30/01/2021
to "Peter" and "jmamos"
P1386033
(16+16) C+
Result? Duplex
1. ... fxg3 2. Dxg3 exf2 3. f4 droht 4. Dxa3# 3. ... fxg1=S+ 4. Lxg1 gxf4 5. Dxa3#
1. ... exf2? 2. Dxf2 fxg3 3. De3 g2,gxh2 4. Dxa3#
play all play one stop play next play all
Full-point zugzwang with full board. 2nd player mates by 4th move at the latest.
Henrik Juel: We cannot deduce who has the move, so we cannot say who wins
If Black has the move, White wins (and vice versa by symmetry)
0... fxg3 1.Dxg3 exf2 2.f4 fxg1=S+ 3.Lxg1 gxf4 4.Dxa3#
0... exf2? 1.Dxf2 fxg3 2.De3 g2,gxh2 3.Dxa3# (2021-01-31)
A.Buchanan: Exactly right, Henrik. I have added “duplex” to the stip as I think it belongs (2021-01-31)
Hans-Jürgen Manthey: in max. 35 Zügen gewinnt Schwarz:
1. d4 e5 2. d5 e4 3. c4 f5 4. f3 c6 5. g4 b5 6. h4 a5 7. h5 a4 8. h6 a3 9. Kf2 Da5 10. Kg3 Da6 11. Kh4 Kd8 12. De1 Kc7 13. Dg3+ Kb6 14. Dh3 Ka5 15. Lg2 Lb7 16. Lf4 Lc5 17. Sd2 Se7 18. d6 e3 19. Sf1 Sc8 20. Sg3 Sb6 21. Tf1 Tc8 22. Tf2 Tc7 23. Lf1 Lc8 24. Dg2 Db7 25. Th3 Ta6 26. Sh1 Sa8 27. Lh2 La7 28. Tg3 Tb6 29. Kh3 Ka6 30. c5 f4
und nun:
31. b4 g5 mit Schwarz gewinnt:
32. cxb6 Dxb6 33. dxc7 c5 34. cxb8S+ Lxb8 35. gxc5 Dxh6#
32. dxc7 Dxc7 33. cxb6 Dd6 34. bxa7, b7 Dxh6#
oder 31. b3 g5 32. b4 mit Weiß gewinnt:
32. ... fxg3 33. Dxg3 exf2 34. f4 fxg1S+ 35. Lxg1 gxf4 36. Dxa3#
32. ... exf2 33. Dxf2 fxg3 34. De3 gxh2, g2 35. Dxa3# (2021-02-01)
comment
Keywords: Construction task, Capture-free, Symmetrical position
Genre: Studies
Computer test: C+ Popeye 4.85
FEN: nnb5/bqrp3p/krpP3P/1pP3p1/1P3pP1/p3pPRK/P3PRQB/5BNN
Input: A.Buchanan, 2021-01-31
Last update: A.Buchanan, 2022-07-27 more...
57 - P1386410
Andrew Buchanan
chess.stackexchange.com 11/02/2021
P1386410
(16+16)
Find a diagram which can recur a maximum number of times, such that it also has a unique KBP (shortest proof game) to its first occurrence.
a) with 3-fold repetition & 50-move rules
b) with 5-fold repetition & 75-move rules
a) e.g. 1. a4 e5 2. a5 e4 3. a6 Sxa6 4. f4
b) e.g. 1. e3 a5 2. La6 e6 3. Se2
play all play one stop play next play all
a) 22 occurrences possible, with 44.5 moves, so no issue with 50-move rule even if it were mandatory.
b) 37 occurrences possible, with 74.0 moves + 0.5 for 3. Se2 in proof game.
The theoretical maximum of 42 is impossible, because it would take 84.5 moves, breaching the mandatory 75-move rule.
Other shortest unique SPGs are possible, but need:
(1) both sides have at least 2 of K,R & R able to move.
(2) both sides must have officer to triangulate.
(3) (for player on the move) triangulating officer must be B or Q.
(4) (for 3+50 case only) e.p. set up.
A.Buchanan: Without German KBP in the stip the animation won't work (2021-02-12)
comment
Keywords: Construction task (non-unique), Synthetic problem, 50 move rule, 75 move rule, Draw by repetition, En passant, Castling, Homebase
Genre: Retro
FEN: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR
Input: A.Buchanan, 2021-02-12
Last update: A.Buchanan, 2024-03-19 more...
58 - P1386489
Aurel M. Karpati
Adrian Storisteanu
Yuri Bilokin
Hans-Jürgen Manthey
Viktoras Paliulionis
Andrew Buchanan

PDB Website 15/02/2021
AK, correction AS, YB, HJM, VP & AB
P1386489
(7+4) C+
h#5
1. b2xa1=S Sc4 2. Sxb3 Se3 3. Sd4 Lc4 4. Sdf3 Lf1 5. Sg1 Lg2#
play all play one stop play next play all
corrects and simplifies P0552475
A.Buchanan: Please forgive me but I think “under-promotion” is only meaningful for directmates and studies. That’s why I had put in promotion as a keyword, not under-promotion. In helpmates, promotions need to be distinguished of course, and we can put in the officer type in the parameter slot. Under-promotion would still need such a parameter because it’s inexact itself: the worst of all worlds. Even for directmates and studies of course some people consider knight promotion not to be an under-promotion at all, but I wouldn’t go that far myself. There are far too many keywords covering promotion, and at some time we should clean them up, but in the mean time I am open to considering another opinion if it is explained to me. Thank you. (2021-02-15)
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comment
Keywords: Promotion (s), Schlüssel = Eckzug, Promotion key (s), Corner mate, Selfblock, Model mate, Entblockung
Genre: h#
Computer test: Popeye v4.85
FEN: 8/8/1N6/3P4/8/1Pp5/BpP4n/NK5k
Input: A.Buchanan, 2021-02-15
Last update: A.Buchanan, 2021-02-18 more...
59 - P1386614
Thomas R. Dawson
Lion Xray
Andrew Buchanan

PDB Website 19/02/2021
TRD, version LX & AB
P1386614
(13+9) C+
#2
1. hxg6ep+ Lg5 2. Dxg5#
R: 1. g7-g5 Te3-e7+ 2. Kg5-h6+ Lf5-h7+ 3. Kf6-g5 Sd6-e8+
play all play one stop play next play all
Black has captured 3 white units. dxcxb accounts for 2. With only one left over, we know that bPh3 never captured. So to explain wPh4, White must have played fxgxh or hxgxh. Combined with dxcxb & exdxcxb, that accounts for all of White's captures.
(a) If White played fxgxh, then the original [wPh] was "waylaid" by an officer, without promoting or capturing.
(b) If White played hxgxh, then the original [wPf] did not capture. We know that [bPf] or [bPg] promoted, using at most one capture.
(b.1) If Black did capture fxg or fxe, then [wPf] did promote to make the balance, and Black's last move can't have been fxg, or the f-file would be blocked to wP.
(b.2) If Black didn't capture fxg or fxe, then [wPf] was waylaid to clear the way for [bPf] to promote.
We don't know which of these three possibilities happened, but in every case:
(1) All captures are accounted for (so e.g. Kg5xSh6 was not possible).
(2) Black did not just play f6xg5.
If Black just played g6-g5, retract prior checking moves and discover retropat as g6 is blocked preventing discovered check by wB now on h7. By elimination, last move was g7-g5 and ep key is ok.
Removes 2 pieces from P1106295, and enriches the retro logic
Henrik Juel: Nice clean-up and careful retro argumentation (2021-02-18)
A.Buchanan: Thanks Henrik - in fact I've just seen that one can uniquely retract a couple of single moves further, see the animation (2021-02-19)
comment
Keywords: En passant as key, Last Moves? (6)
Genre: 2#, Retro
Computer test: HC+ retro musing + Popeye v4.85
FEN: 3KN3/rPp1R2B/pp5k/Q5pP/PPP4b/1p4Pp/1P6/2B5
Input: A.Buchanan, 2021-02-18
Last update: A.Buchanan, 2021-04-16 more...
60 - P1386615
Evgeny Balashov
Andrew Buchanan
Joost de Heer

Facebook 14/01/2021
EB, version AB & JdH
P1386615
(5+7) C+
s#4
1. Lb5! g3 2. f3
2. ... c5,c6 3. Lc4,Lc6 e5,dxe6 4. dxe6ep g2#
2. ... e5,e6 3. dxe6ep,dxe6 c5,c6 4. Lc4,Lxc6 g2#
1. ... c5,c6 2. Lc4,Lxc6 g3 3. f3 e5,e6 4. dxe6ep,dxe6 g2#
2. ... e5,e6 3. dxe6ep,dxe6 g3 4. f3 g2#
1. ... e5,e6 2. dxe6ep,dxe6 g3 3. f3 c5,c6 4. Lc4,Lxc6 g2#
2. ... c5,c6 3. Lc4,Lxc6 g3 4. f3 g2#
play all play one stop play next play all
Version of P1262214
Henrik Juel: 1.Lb5
Lb5 captures or blocks Pc7, Pd5 captures Pe7
Whenever Black plays g4-g3, White immediately responds with f2-f3 (2021-02-18)
comment
Keywords: En passant (x2)
Genre: s#
Computer test: C+ Popeye v4.85
FEN: 8/2p1p3/8/3P1p2/5Ppp/3B3k/5P1p/7K
Input: A.Buchanan, 2021-02-18
Last update: A.Buchanan, 2021-10-25 more...
61 - P1386621
Andrew Buchanan
1 Problemas , p. 1050, 01/2021
motto: "Fake Gnus!"
P1386621
(12+15) C+
PG in 8.5
Gnus instead of knights
sSR=Gnu
wSR=Gnu
1. f4 GNc5 2. f5 GNxd2 3. f6 GNxg1 4. Dxd7+ GNxd7 5. Kd1 GNxe2 6. Tg1 GNf5 7. La6 GNfg8 8. c4 GNb8+ 9. Kc2
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Henrik Juel: Solution
1.f4 GNc5 2.f5 GNxd2 3.f6 GNxg1 4.Qxd7+ GNxd7 5.Kd1 GNxe2 6.Tg1 GNf5 7.La6 GNfg8 8.c4 GNb8+ 9.Kc2
As intimated by the motto, the black Gnus have switched places
TRD's classical fairy men, Grasshopper and Nightrider, are traditionally depicted by rotating a queen and a knight 180 degrees; so I would prefer the Gnus here represented by a 90 degrees rotation (either way) (2021-02-19)
A.Buchanan: Hi Henrik thanks for the "orientation on orientation" :) I have pivoted the knights. The 100 gnu problems in PDB are 30 L, 20 U & 50 R, so I've gone for the last (2021-02-19)
comment
Keywords: Unique Proof Game, Impostor (gn gn), Homebase (s)
Pieces: sr = Gnu (GN)
Genre: Retro, Fairies
Computer test: C+ WinChloe v3.52
FEN: r*1nbqkb*1nr/ppp1pppp/B4P2/8/2P5/8/PPK3PP/R*1NB3R1
Input: A.Buchanan, 2021-02-19
Last update: A.Buchanan, 2021-11-02 more...
62 - P1386625
Andrew Buchanan
4 Problemas , p. 1052, 01/2021
P1386625
(16+16) C+
a) h#2
b) SPG to game array diagram but with *Black* to move
Köko Okök
Grasshoppers instead of queens
a) 1. h6! (1.h5? Köko) Gb3 2. Th7 Gxg8#
b)
1. ... Sc3 Gd6 2. Sd5 Gd4 3. Sc3 Gd8 4. Sb1
Tries:
1. ... Sf3 Gf6 2. Se5 Gd4 3. Sf3 Gd8? Okök 4. Sg1
1. ... Sf3 Gd6 2. Sd4? Köko Gd3 3. Sf3 Gd8 4. Sg1
1. ... Sf3,Sh3 Gf6 2. Sg5 Gh4+ 3. Sf3 (3. Sh3? still in check Gd8) Gd8? Okök 4. Sg1
Fun tries: two uses of each condition!
play all play one stop play next play all
Henrik Juel: Nice Fake series, Andrew
Tiny typo, hidden:
Your Okök definition
'A piece can move only it is in contact with another piece.'
seems to have an 'if' or a 'when' missing (2021-02-19)
A.Buchanan: Fixed, thanks (2021-02-19)
comment
Keywords: Unique Proof Game, Köko, Okök, Fake game array, Homebase (2), Initial Game Array (2), Twinning by continuation
Pieces: du = Grasshopper (G)
Genre: h#, Retro, Fairies
Computer test: C+ WinChloe v3.52
FEN: rnb*2qkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNB*2QKBNR
Input: A.Buchanan, 2021-02-19
Last update: A.Buchanan, 2022-02-16 more...
63 - P1388086
Vladimir Koci
Andrew Buchanan

540a OzProblems.com 03/04/2021
P1388086
(3+10) C+
h#5
(3 solutions)
1. De5+ dxe5 2. Sf6+ exf6 3. Tc3 f7 4. T3c1 f8=D 5. c3 Df2#
1. Sc3 d5 2. Dg3 d6 3. Ld3 d7 4. Le2 d8=L 5. De1 Lg5#
1. Dc5 dxc5 2. Sb6 cxb6 3. Kc3 b7 4. Kb3 b8=D 5. c3 Dxb5#
play all play one stop play next play all
Peter Wong (OzProblems): "While dispensing with two black pawns, this setting renders a different queen promotion in [a new] third solution which ends in another model mate."
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comment
Keywords: Promotion (D,D,L), Model mate (3)
Genre: h#
Computer test: C+ Popeye 4.61
FEN: 4K3/7b/3q4/1p1n4/2pP4/r7/3k2p1/nB1r4
Input: A.Buchanan, 2021-04-03
Last update: A.Buchanan, 2023-12-04 more...
64 - P1388090
Yuri Bilokin
Andrew Buchanan

PDB Website 03/04/2021
after Martin Gohn
P1388090
(3+7) C+
h#5
1. Kd7 g4 2. Lh1 Lg2 3. Ke6 Lh3 4. Ld5 g5+ 5. f5 gxf6ep#
play all play one stop play next play all
correction of P0505412 with greater economy
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comment
Keywords: Bahnung, En passant as mating move, Model mate
Genre: h#
Computer test: C+, Gustav 4.1d, Brute Force
FEN: B4n2/1bk2pKn/3q4/4p3/8/8/6P1/8
Input: A.Buchanan, 2021-04-03
Last update: A.Buchanan, 2021-11-22 more...
65 - P1388091
Andrew Buchanan
James Malcom

PS3645 The Problemist Supplement 171, p. 139, 03/2021
P1388091
(5+9) C+
#10
1. h7! dxc2 2. h8=S d3 3. Sg6 d4 4. Sf4 d5 5. Sxd3 d6 6. Sxb4 d3 7. Sxd3 d4 8. b4 d5 9. Sc5 d3 10. Sb3#
play all play one stop play next play all
Henrik Juel: C+ Popeye 4.61
At first sight I thought that 1.h7 Lxc2 2.h8=DL thr. 3.DLxd4# would be a cook
but Black defends better by 1... dxc2!
Very impressive that the main variation is dual-free (2021-04-03)
comment
Keywords: Promotion (S)
Genre: n#
Computer test: C+ Popeye 4.61
FEN: 8/3p4/3p3P/3p4/1p1p4/1P1p4/p1PP4/kbK5
Reprints: Facebook 02/04/2021
Input: A.Buchanan, 2021-04-03
Last update: Felber, Volker, 2021-12-16 more...
66 - P1388527
Andrew Buchanan
Retros mailing list 14/04/2021
dedicated to Theodore Hwa
P1388527
(16+14) C+
a) White to move. Last move?
b) KBP in 4.0
b) 1. e4 Sa6 2. Lxa6 f6 3. Lc4 a6 4. Lxg8 Ta7
a) R: 1. ... Ta8.a7
play all play one stop play next play all
See also: P1012898 & P1323914
Henrik Juel: C+ Euclide 1.01
1. Be2-e4 Sb8-a6 2. Lf1xa6 Bf7-f6 3. La6-c4 Ba7-a6 4. Lc4xg8 Ta8-a7
With White to move, last move could not be f7-f6, so it was Ta8-a7 (2021-04-14)
A.Buchanan: That was quick, Henrik! This is the first PDB problem validated by Retractor 2.0! Note that Black could also not have just played Kf7-e8. (2021-04-14)
Henrik Juel: Actually, I solved part a) by hand, but now it has been verified by Retractor 2.0, so your Computer test stuff is correct, Andrew (2021-04-14)
A.Buchanan: In principle, one could chain the output of an SPG engine into Retractor, to see if any other compositions with this stipulation can exist. Beyond trivial pawn nudges, maybe 3 is the lot? (2021-04-15)
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comment
Keywords: Unique Proof Game, Last Move?, Type B
Genre: Retro
Computer test: C+ Retractor 2.0 Last move? C+ Euclide 1.01 SPG
FEN: 2bqkbBr/rpppp1pp/p4p2/8/4P3/8/PPPP1PPP/RNBQK1NR
Input: A.Buchanan, 2021-04-14
Last update: Alfred Pfeiffer, 2021-04-29 more...
67 - P1388687
Andrew Buchanan
Retros mailing list 16/04/2021
P1388687
(11+16) C+
Last two single moves?
b) KBP in 9.0
b) 1. Sf3 d6 2. Se5 dxe5 3. Sc3 Dd5 4. Se4 Dxa2 5. Sg3 Db3 6. Ta4 Da3 7. Tf4 exf4 8. h3 fxg3 9. Th2 gxh2
a) R: 1. g3xTh2 Th1-h2
play all play one stop play next play all
Henrik Juel: Part a)
Black has captured [Pa2] on its file, because White never captured, and dxexfxg-g3xTh2, because [Th1] fell in its corner
White has no possible last move, so Black made the last move
Not R: 1... DxPa3? 2.a2-a3, preventing [Ta1] from coming home
R: 1... g3xTh2 2.Th1-h2 (2021-04-17)
Henrik Juel: Part b) C+ Euclide 1.01 (no solution in 8.5 moves)
1. Sg1-f3 Bd7-d6 2. Sf3-e5 Bd6xe5 3. Sb1-c3 Dd8-d5
4. Sc3-e4 Dd5xa2 5. Se4-g3 Da2-b3 6. Ta1-a4 Db3-a3
7. Ta4-f4 Be5xf4 8. Bh2-h3 Bf4xg3 9. Th1-h2 Bg3xh2
Good problem, Andrew (2021-04-17)
Mario Richter: Retractor 2.0 gives 74 possible last moves, so calling a) "C+ Retractor 2.0 + elimination of false positives" sounds a little bit strange to me. (2021-04-17)
A.Buchanan: Yes you are right Mario: I wanted to be encouraging. I should have written HC+, but even that is a stretch. I suggested to Theodore Hwa that he contact you. What does rawbats make of this problem, may I ask? (2021-04-18)
comment
Keywords: Unique Proof Game, Last Moves? (2), Type A
Genre: Retro
Computer test: a) HC+ Retractor 2.0 + elimination of false positives b) C+ Euclide 1.01 (no solution in 8.5 moves)
FEN: rnb1kbnr/ppp1pppp/8/8/8/q6P/1PPPPPPp/2BQKB2
Reprints: Facebook 17/04/2021
www.thbrand.de 17/04/2021
Input: A.Buchanan, 2021-04-17
Last update: A.Buchanan, 2021-10-31 more...
68 - P1388688
Andrew Buchanan
Retros mailing list 16/04/2021
P1388688
(16+15) C+
(a) Last move?
(b) KBP in 3.5
b) 1. c3 f5 2. Db3 Sf6 3. Dg8 f4 4. Dxf8+
a) R: 1. ... Dg8xLf8+
play all play one stop play next play all
Henrik Juel: Part a)
Last move was Dg8xLf8+
Part b) C+ Euclide 1.01
1.c3 f5 2.Db3 Sf6 3.Dg8 f4 4.Dxf8+
Little solver challenge (2021-04-17)
comment
Keywords: Unique Proof Game, Last Move?, Type C
Genre: Retro
Computer test: a) Retractor 2.0 b) C+ Euclide 1.01
FEN: rnbqkQ1r/ppppp1pp/5n2/8/5p2/2P5/PP1PPPPP/RNB1KBNR
Input: A.Buchanan, 2021-04-17
Last update: A.Buchanan, 2021-04-17 more...
69 - P1389166
Andrew Buchanan
Retros mailing list 12/12/2012
P1389166
(2+1) C+
#3
b) Capture the King: win in 2 moves
a) 1. Kf6 Kh7 2. f8=T Kh6 3. Th8#
b) 1. Kg6 Kg8 2. fxg8=D,T,L,S
1. ... Kg7,Kh7 2. Kxg7,Kxh7
play all play one stop play next play all

Duplicate Diagram: P1013439

zu a) s. z.B. P1133499
Henrik Juel: part a) is C+ Popeye 4.61
1.Kf6 Kh7 2.f8=T Kh6 3.Th8#
part b) is damaged by a promotion dual...
1.Kg6 Kg8 2.fxg8=DTLS, 1... Kg7,Kh7 2.KxK (2021-05-02)
A.Buchanan: The point about promotion dual hadn't occurred to me: interesting! On reflection, I think it's like the tolerated dual in regular chess, where if the mating move is =Q/R or =Q/B that's ok, because it would be unreasonable to exclude from soundness all promotion mates where the mated king is not very near to the promoted unit. Similarly here, the promotion captures the opposing king, so the promotion choice is academic. Nevertheless, we would not wish to render unsound *all* king-capturing promotion moves, so we need a tolerated dual! Ground-breaking! :D Thanks so much (2021-05-02)
SP: Herr Buchanan: You are not claiming to have composed part (a), are you?
It has been published by several others. (2023-01-08)
A.Buchanan: The contrast between the two win conditions is the entire point. However this must be represented using the a)&b) notation, which gives the impression that each twin is separate. The composition was just a self-published schema anyway, so who cares? (2023-01-09)
comment
Keywords: Capture the King, Kindergarten Problem, Minimal, Miniature, Tolerated dual promotion (DTLS)
Genre: 2#, 3#, Fairies
Computer test: HC+ Popeye 4.61 part a ok part b has "tolerated dual" for Capture the King stip :-)
FEN: 7k/5P2/8/5K2/8/8/8/8
Reprints: chess.stackexchange.com 2/5/2018
Discord Chess Problems & Studies Server 2/5/2021
Input: A.Buchanan, 2021-05-02
Last update: Mario Richter, 2023-01-09 more...
70 - P1389167
Noam D. Elkies
Andrew Buchanan

v Retros mailing list 21/12/2012
NDE, version AB
P1389167
(3+6)
#1
b) Capture the King: win in 3 moves
a) 1. Sg3#
b) 1. Lf2 e1=D,L,T,S 2. Sg3 Db4,~ 3. Sxh1
play all play one stop play next play all
more ...
comment
Keywords: Capture the King, Stalemate dissolution
Genre: 3#, Fairies
FEN: 8/8/8/5N2/K7/8/4p1pp/4Bbrk
Reprints: chess.stackexchange.com 2/5/2018
Discord Chess Problems & Studies Server 2/5/2021
Input: A.Buchanan, 2021-05-02
Last update: Alfred Pfeiffer, 2021-08-02 more...
71 - P1389168
Noam D. Elkies
Andrew Buchanan

Retros mailing list 21/12/2012
NDE, version AB
P1389168
(3+7)
#1
b) Capture the King: win in 3 moves (2 solutions)
a) 1. Sf7#
b1) 1. Kg4! g5 2. Sf7 Lf5,L~ 3. Sxh8
1. Kf4,Kh4? g5 2. Sf7 gxf4,gxh4!
b2) 1. Sxg6! Lxg6 2. Kxg6 Kh7 3. Kxh7
1. Sf7=,S~=?
play all play one stop play next play all
more ...
comment
Keywords: Capture the King, Stalemate dissolution
Genre: 3#, Fairies
FEN: 5brk/4p1pb/4P1p1/4N1K1/8/8/8/8
Reprints: Discord Chess Problems & Studies Server 2/5/2021
Input: A.Buchanan, 2021-05-02
Last update: A.Buchanan, 2021-10-24 more...
72 - P1389169
Thomas R. Dawson
Andrew Buchanan

PDB Website 14/10/2019
TRD, correction AB
P1389169
(4+5) C+
h#2
1. d4 Sg6 2. Tg5 Ta6#
play all play one stop play next play all
See P0515072
Henrik Juel: C+ Popeye 4.61
1.d4 Sg6 2.Tg5 Ta6#
pawn asymmetry (2021-05-02)
A.Buchanan: Yes Henrik exactly - every symmetry has to be broken somehow to make the solution unique, and here the point is that the symmetry is just visual, broken by the pawn movement rules (2021-05-02)
comment
Keywords: Symmetrical position, Asymmetrical solution, Model mate
Genre: h#
Computer test: C+ Popeye 4.61
FEN: 5N1K/8/5k1N/1r1p4/4p3/8/4r3/R7
Input: A.Buchanan, 2021-05-02
Last update: A.Buchanan, 2021-05-08 more...
73 - P1389195
Andrew Buchanan
PDB Website 02/05/2021
P1389195
(12+12) C+
#1
PG in 8.0
1. h4 Sf6 2. h5 Se4 3. h6 Sxd2 4. hxg7 Sb3 5. gxf8=S Sxa1 6. Sxh7 Sxc2 7. Dxc2 Txh7 8. Dd1 Th8
play all play one stop play next play all
See P1389196 for the companion.
more ...
comment
Keywords: Unique Proof Game, Homebase (2)
Genre: Retro
Computer test: Popeye v4.85
FEN: rnbqk2r/pppppp2/8/8/8/8/PP2PPP1/1NBQKBNR
Input: A.Buchanan, 2021-05-02
Last update: A.Buchanan, 2021-05-20 more...
74 - P1389196
Andrew Buchanan
PDB Website 2/5/2021
P1389196
(12+11) C+
#1
PG in 8.0
1. c4 b5 2. Db3 bxc4 3. Dxb8 La6 4. Dxa7 Db8 5. Dxa6 Dxb2 6. Dxc4 Dxc1 7. Dxc1 Txa2 8. Dd1 Ta8
play all play one stop play next play all
In full agreement with the organizer of the Discord #1 tourney, someone asked me to post two problems now. They are not entered in the competition, but are registered here in order to avoid later potential anticipation. The author's name will be made public when the Discord results are announced :) Feel free to solve them and comment on them. See P1389195 for the companion.
Henrik Juel: A nice couple of shorties
What is the prize for guessing the author? (2021-05-02)
A.Buchanan: I don't know the prize: I will ask the author when I relay your kind words. Maybe it's a fraction of the prize given for the Discord #1 competition itself? (I.e. glory only.) Apparently a third problem of this set was submitted to the competition (you can probably guess the mate), and the composer was concerned that the publication of that one might cause imaginative folks to construct these other two.
To my mind, this one here is the most interesting of the three.
In any case, all will be revealed very soon. (2021-05-16)
A.Buchanan: Well, bless my soul - look who the author turned out to be :D (2021-05-20)
Henrik Juel: The chess problem community at large may be stunned by this revelation
But not all of us... (2021-05-21)
more ...
comment
Keywords: Homebase (2), Unique Proof Game
Genre: Retro
Computer test: Popeye v4.85
FEN: r3kbnr/2pppppp/8/8/8/8/3PPPPP/RN1QKBNR
Input: A.Buchanan, 2021-05-02
Last update: A.Buchanan, 2021-05-20 more...
75 - P1389375
Andrew Buchanan
MatPlus.net Forum 22/01/2021
P1389375
(14+14) C+
PG in 7.0
Staugaard castling
1. g3 e6 2. Lg2 e5 3. Lxb7 e4 4. Sf3 exf3 5. 0-0 fxe2 6. Lxa8 e1=T 7. Lg2 0-0-0-0-0-0
play all play one stop play next play all
Objective: fastest Staugaard (Pam-Krabbé) + another castling (happens to be kside)
A.Buchanan: Now we know more about Conrad Staugaard and his life, I enthusiastically agree with Henrik's earlier suggestion that we change this theme to be "Staugaard", which would also align with WinChloe. I can make necessary changes in PDB as a batch, and retain also "Pam-Krabbe" as a deprecated keyword, pointing to Staugaard. Pam & Krabbé are famous already, and only popularized Staugaard's funny idea. Any objections? (2021-05-08)
A.Buchanan: OK thank you: I've made the move. Please check the definitions, and let me know anything that needs changing (2021-05-09)
Henrik Juel: Very good, Andrew; the Staugaard fan club (both of us) thanks you
You might want to add that after a white Staugaard castling, wK is on e3 and promoted wR is on e2
I wonder whether the solution notation should be changed to 0-0-0-0-0 with 5 zeroes, so that the number of zeroes is one less than the length of the rook displacement for all three castlings (2021-05-09)
Henrik Juel: Forget my very last remark, please
Short and long castling has rook displacement = number of zeroes,
so Staugaard should remain with 6 zeroes, of course (2021-05-09)
A.Buchanan: Ok listed the target squares as requested. (2021-05-09)
A.Buchanan: Curious that this economy record must begin with a tempo move (2021-05-20)
A.Buchanan: Staugaard seems a much better basis than Chess960 for further generalization of castling. Basically move an unchecked royal king 2 unattacked square towards the rook, and the rook hops the otherside. This works whatever the gap between the two. This is more similar to rokagogo. (2021-05-21)
more ...
comment
Keywords: Unique Proof Game, Staugaard castling, Castling (2), Phoenix (t), Promotion (t), Tempo Loss, Economy record, Pure Round Trip (L3)
Genre: Retro, Fairies
Computer test: HC+ no orthodox solution in 7.0, and last Bl move can only have been 0^6 (else switchback, taking more than 7 Bl moves in total). Retracting 0^6, C+ Euclide 1.01 in 6.5
FEN: 1nbq1bnr/p1pprppp/4k3/8/8/6P1/PPPP1PBP/RNBQ1RK1
Input: A.Buchanan, 2021-05-08
Last update: Rainer Staudte, 2024-02-28 more...
76 - P1389458
Lord Dunsany
Andrew Buchanan

PDB Website 11/05/2021
"No more cross-capturing to inconvenience you, Milord."
Lord Dunsany, correction AB
P1389458
(10+9) C+
#3
1. 0-0-0! droht 2. Txb7 droht 3. Tb8#
1. ... Kd8 2. Txa6+ b6,Kc8,Ke8 3. Ta8#
play all play one stop play next play all
Mutex castling
Corrects P1323157.
Henrik Juel: If both White and Black can castle, there is no way to explain sTh7
If only White can castle, both black rooks are original
If only Black can castle, sTh7 is a promoted pawn
So the castlings are mutually exclusive, and the solution
1.0-0-0 thr. 2.Txb7 thr. 3.Tb8# is C+ Popeye 4.61 (2021-05-11)
Henrik Juel: I had a hard time finding the correct Popeye input, which is 'opt cas a1h8'
Good work, Andrew; if you continue like this, you may expect a peerage letter from the british queen, provided Scotland stays in the union... (2021-05-11)
A.Buchanan: Thanks Henrik: yes I can never remember these parameters, but Olive gave me a hint after I got it wrong :) I replaced wSa7 by wLa5 for an extra variation. These problems were just Christmas puzzles for Dunsany every year in the main Literary magazine of the time. So I fix it in that spirit, but I'm sure I've seen other more intricate problems where both sides have one side boxed in by possibly cross-capturing pawns depending on capture-counting (2021-05-11)
Henrik Juel: The additional variation is 1... Kd8 2.Txa6+ b6,Kc8,Ke8 3.Ta8#
Still C+ Popeye 4.61 (2021-05-11)
comment
Keywords: Castling
Genre: 3#, Retro
Computer test: HC+ simple retro thinking + Popeye v4.85
FEN: 4k2r/1p1p1p1r/pRpP1P2/B6p/8/7P/1PP3P1/R3K3
Input: A.Buchanan, 2021-05-11
Last update: A.Buchanan, 2021-07-09 more...
77 - P1389660
Werner Kuntsche
Andrew Buchanan

PDB Website 14/05/2021
WK, correction AB
P1389660
(10+11) C+
h#2
1. exd3ep g5 2. Lb3 Se6#
play all play one stop play next play all
HJ: Black captured all six missing white men with dxe, exfxgxh, and fxgxh.
So White captured all five missing black men with axb, bxa, cxb/d, and e2xf3xg4, and promoted twice.
Last move was d2-d4, because all other attempts give illegal checks, so the ep key is legitimized.
Corrects P1389486
more ...
comment
Keywords: En passant as key
Genre: h#, Retro
Computer test: HC+ Popeye 4.61 with analysis
FEN: 8/6pp/7b/7P/P1kPpNPR/n1p2B1p/p4PPp/2Kb4
Input: A.Buchanan, 2021-05-16
Last update: A.Buchanan, 2021-05-16 more...
78 - P1389698
Andrew Buchanan
Retros mailing list 04/2007
after Bernd Schwarzkopf
P1389698
(12+10)
Last 15 single moves?
Duplex
See http://abrobecker.free.fr/chess/lengths.pdf
Henrik Juel: R: 1.h7-h8=L Lg1-h2 2.h6-h7 Lh2-g1 3.h5-h6 Lg1-h2 4.h4-h5 Lh2-g1 5.h3-h4 Lg1-h2 6.h2-h3 h3xLg2 7.Lh1-g2 h4-h3 8.Lg2-h1
R: 1... Lg1-h2 2.h7-h8=L Lh2-g1 3.h6-h7 Lg1-h2 4.h5-h6 Lh2-g1 5.h4-h5 Lg1-h2 6.h2-h4 h3xLg2 7.Lh1-g2 h4-h3 8.Lg2-h1 h5-h4 (2021-08-18)
comment
Keywords: Last Moves?, Type D, Non-standard material (l), Obvious promotion (Ll)
Genre: Retro
FEN: 7B/1p1p2p1/8/8/1P6/1PPPkPP1/NPK1bppb/NQn2b2
Reprints: VIII Length Records in Last Single Moves? 11/2009
Input: A.Buchanan, 2021-05-17
Last update: A.Buchanan, 2021-10-13 more...
79 - P1390561
Guus Rol
Andrew Buchanan

Discord Chess Problems & Studies Server 02/05/2021
5th Place
Discord Composition Tourney 1
P1390561
(15+9)
#1
1. Dd2!#
1. 0-0-0?#
R: 1. Kc3-d3 De4-b4+ ( 2. Kd3-c3 Db4-e4 retro loop)
2. Kb2-c3 Lb4-a3+ ( 3. Kc3-b2 La3-b4+ retro loop)
3. Kb1-b2 Ta2-a1,Ta3-a1+
play all play one stop play next play all
Authors' solution: hey wait: so is there a dual? Well no. What was Black's last move? Let's look at all the captures & promotions first:
White: captured P promoted RRRRRBS
Black: captured QRRBBSS promoted -

bPs all on original columns: no black cross-captures. So 7 wPs captured once and promoted. The exception must have been poor wPh, because it can't get past bPh anyway, and was waylaid on its starting file by an officer. Other wPs captured as axb, bxc, cxd, dxc/e, exd, fxe, gxh before promoting.

The sequence of bP moves must have been one of:
(i) bPc6 (allows wPd to pass) then bPd5 (allows promoted rooks to escape) then bPe6 (when all the rooks are out, letting wPf to pass)
(ii) bPe6 then bPd5 then bPc6.

So which? In (i) the units promoting late on e8 & h8 must have been S & B, as the door was closed on escaping rooks. But e8 is a light square, and h8 is blocked by bPg7 which never moved. So neither could have promoted to B. Therefore it was option (ii), pawn move sequence roughly:
bPe6 & bPh6
gxh=R, fxe=R, dxe=R,
bPd5
exd=R, cxd=R
5 Rs all exit
bPc6
bxc=S
bPb6
axb=B

Bottom line: all the bP moves and captures were historical, and so it must be bK which just moved. We can now use Retractor 2 program from Theodore Hwa at http://xenon.stanford.edu/~hwatheod/retractor2/retractor.html to validate our manual analysis of the retro play, ignoring any suggestions which involve capture. So wRa had already moved: no castling now.
Henrik Juel: Black captured [Ph2] with an officer
The other white pawns captured all missing black men to promote seven times
Last move was not made by a black pawn as this would ruin the promotions, so it was Kc3-d3
Retroplay: 1... Kc3-d3 2.De4-b4+ Kb2-c3! 3.Lb4-a3+ Kb1-b2! 4.Ta3-a1+ or Ta2-a1+ (other K retractions just postpone the inevitable), so 1.0-0-0 is illegal
1.Dd2#
Good problem, maybe the best in the tourney (2021-06-08)
A.Buchanan: Thanks Henrik. Can you figure out which pawns promoted to which kind of officers on which squares? (2021-06-09)
Henrik Juel: No, I would expect there were several feasible promotion patterns
But the need to move [Pb7c7d7e7] very carefully can easily make your suggestion correct
Offhand I do not see the right sequence, so you are welcome to enlighten me (2021-06-10)
Henrik Juel: I think I got it
(promote [Pg2] to rook on h8 at some early time)
first e7-e6, promote [Pd2f2] to rooks on e8
then d7-d5, promote [Pc2e2] to rooks on d8
get all promoted rooks out
finally [Pb2] promotes to knight on c8 and [Pa2] to bishop on b8 (2021-06-10)
A.Buchanan: Exactly! If you try the other way round, there’s nowhere to promote B (2021-06-10)
comment
Keywords: Non-standard material (TTTTTLS), Cant Castler
Genre: Retro
Computer test: HC+ Popeye v4.85 Retractor v2.0 + thinking
FEN: 8/p4pp1/1pp1p2p/1RBpR3/RQ3RB1/BN1k4/2N3NR/R3K2R
Reprints: Facebook 28/05/2021
Input: A.Buchanan, 2021-06-08
Last update: A.Buchanan, 2021-06-11 more...
80 - P1390567
Andrew Buchanan
Discord Chess Problems & Studies Server 02/05/2021
P1390567
(12+12) C+
#1
PG in 8.0
1. h2-h4 Sb8-c6 2. h4-h5 Sc6-d4 3. h5-h6 Sd4xe2 4. h6xg7 Se2-g3 5. g7xh8=S Sg3xh1 6. Sh8xf7 Sh1xf2 7. Ke1xf2 Ke8xf7 8. Kf2-e1 Kf7-e8 9. Dh5#
play all play one stop play next play all
Henrik Juel: The proof game was harder to solve than the #1...
more ...
comment
Keywords: Unique Proof Game, Homebase (2), under-promotion (S), Excelsior white
Genre: Retro
Computer test: Euclide 1.01
FEN: r1bqkbn1/ppppp2p/8/8/8/8/PPPP2P1/RNBQKBN1
Input: A.Buchanan, 2021-06-08
Last update: Alfred Pfeiffer, 2021-09-30 more...
81 - P1390927
Andrew Buchanan
v MatPlus.net Forum 26/06/2021
after Bedrich Formanek
P1390927
(11+2)
#1 (-:
9 solutions
PPRA (Partial PRA = PRA except ignore cases having no solution)
1) 1. g8=CM# R: 1. Kg6xCMh5 CMe4-h5+
2) 1. g8=AD# R: 1. Kg6xADh5 ADc2(d3,e4)-h5+++
3) 1. c8=GZ# R: 1. Kg6xGZh5 GZc2-h5+
4) 1. c8=GQ# R: 1. Kg6xGQh5 GQc2-h5+
5) 1. b8=GF# R: 1. Kg6xGFh5 GFd3-h5+
6) 1. bxa8=GE# R: 1. Kg6xGEh5 GEe4-h5+
7) 1. b8=N# R: 1. Kg6xNh5 Nd3-h5+
8) 1. g8=QN# R: 1. Kg6xQNh5 QNe4-f6-h5+
9) 1. h8=TP# R: 1. Kg6xTPh5 TPf5-h5+
Minor duals, with both mates separately provided elsewhere:
1) 1. g8=GR,b8=GR# R: 1. Kg6xGRh5 GRd3(e4)-h5+
2) 1. g8=MG,h8=MG# R: 1. Kg6xMGh5 MGc2(d3,e4)-h5+
play all play one stop play next play all
What was Black's last move? It can only have been Kg6-h5, fleeing check. But what was White's prior move: it could only have been a fairy piece moving to h5 from the diagonal c2-f5, discovering check. Then this piece was captured by bK. What kind of piece was it? The idea is that for each feasible piece, there should be exactly one corresponding promotion mate.

1) Camel = (1,3)-Leaper
2) Eagle
3) Gazelle = (3-5)-Leaper
4) Giraffe Quintessence = right-angle turn Girafferider, Giraffe = (1,4)-Leaper
5) Greater Leafhopper
6) Greater Treehopper
7) Nightrider
8) Quintessence = right-angle turn Nightrider
9) Rookhopper

Minor duals, where both solutions are separately provided elsewhere:
1) Gnurider
2) Marguerite = Eagle+Grasshopper+Hamster+Moose+Sparrow, only the first two sub-creatures are used)

Tries:
1)It looks as if one might rotate the board 180 degrees: 1. Bb3#! Not 1. b3+? Kxa3!
The position is legal because e.g. R: 1. g8=B+.
However this doesn't work because it's not thematic :)
2) It looks as if R: 1. Kg6-h5 c2-c3+ might be good. Who's to say in a fairy form that wL can't begin on b1? Well if you can show me a fairy piece which can throw other pieces around the board, then let's consider it, but fairy conditions are excluded here, for sanity's sake.

Would be cooks - but the soundness is protected by the halo of PPRA :)
Bishop Eagle, Boy Scout, Dabbaba, Equihopper, Lancer, Moarider Lion, Radial Leaper
AB: See P0001924. Bedrich Formanek is happy with his problem, but welcomes a larger zoo.

I think this is a kind of PRA problem (although PRA is defined currently only for castling and ep). A PRA problem is regarded has having one solution with many parts. So maybe that points the way how to stipulate the problem. The joke version PRA (= Partial PRA) says that PRA applies to all the parts that it does, but not to the others, particularly those with no solution).

It's clear that there are more pieces which would solve the problem. Why not Gnurider or Gazellerider instead of Gnu or Gazelle? Why not Gnurider instead of Nightrider? Etc. Why not Grasshopper instead of Rookhopper? The PRA notion would prevent these from cooking the problem: each is indeed a separate part. As long as whatever was just captured can be uniquely reborn to deliver mate, the problem is sound. The published solution shows the most basic representative piece for each of the patterns, with no unused capability.

As a PRA problem, if a kind of fairy piece might legitimately have been captured on h5, yet does not offer a mating promotion, that would make the problem unsound. And indeed there are two such creatures known: Dabbaba and Lancer. However fortunately we are working with the looser PPRA meta-convention which only applies where it applies.

In earlier versions, the eagle was considered a try, but actually I think it implied an insoluble PRA part, but fortunately could be fixed.
Henrik Juel: if last move was Kg6xGh5, 1.gxh8=G#
if last move was Kg6xYh5 (Y=1,3-S=Camel), 1.g8=Y#
if last move was Kg6xYh5 (Y=rookhopper), 1.gxh8=Y# (This looks like a cook)
if last move was Kg6xYh5 (Y=5,3-S), 1.c8=Y#
if last move was Kg6xNh5, 1.b8=N# (2021-06-20)
A.Buchanan: Thanks Henrik - as discussed: I don’t think Rookhopper is a cook, but is a separate part of the PRA solution. Maybe it’s the fundamental solution and Grasshopper is the one with unneeded additional functionality but Grasshopper is the more common one. Nice for some of these unfamiliar creatures to get some exposure... (2021-06-20)
comment
Keywords: Joke (PPRA), Phoenix (9), Last Moves?, Partial Retro Analysis (PRA), Rex solus, Promotion (9), Minimal
Pieces: tu = Rookhopper (TP), sr = Camel (CM), su = Nightrider (N), lu = Gazelle (GZ), dl = Eagle (AD), sl = Quintessence (QN), lr = Giraffe Quintessence (QG), du = Greater Treehopper (GE), dr = Greater Leafhopper (GF)
Genre: Retro, Fairies
FEN: b7/1PP3PP/7B/6Pk/8/2P3K1/P3P3/1B6
Input: A.Buchanan, 2021-06-19
Last update: A.Buchanan, 2022-01-09 more...
82 - P1391117
Andrew Buchanan
Discord Chess Problems & Studies Server 26/06/2021
P1391117
(3+0)
If playing chess on a 5x5 toroidal board, which is abstractly the most powerful: a bishop, a knight or a rook?
[Example pieces are shown in the diagram for visual jollity, particular locations don't matter.]

All 3 pieces can move to 8 squares in 1 move, and any square on the board in 2 moves. Indeed any two directions can be mapped by a linear transformation onto any two directions. I.e. any of these pieces, which can be regarded as moving in two directions, can be transformed to any other, or indeed to a "chimera" e.g. something which moves N-S, or diagonally NW-SE: half-rook and half-bishop.

So given that all of these lines are equivalent, how could one piece be better than another? Bishops and rooks are riders, so can be blocked, even on a torus. So for example Ra1 cannot move to a3 if a2 & a4(or a5) are blocked. However, the knight remained a leaper. Although the 4 squares accessed by a left knight-move (two squares away, then one to the left) do fall on a straight line on the 5x5 Torus, the knight cannot be blocked from accessing any of them. Similarly for right knight-moves.

There are 6 straight line directions on the 5x5 torus, so there are 15 pieces one might conceive which can move on exactly 2 lines. Three are the orthodox R,B,S, and 12 are chimerae. The knight is the most powerful of the 15. The 8 chimerae which share half the knight DNA are the next most powerful, blockable only on one of their two lines, while the 6 with no knight DNA (rook, bishop and 4 chimerae) are the weakest.
Henrik Juel: Your very first sentence is probably right, Andrew, but I am not convinced
I can see that TLS all can move to eight squares in one move
and it is clear that T (and probably L) can reach all 25 squares in two moves
But how does Sc3 reach a1 in two moves? (2021-06-27)
Henrik Juel: Never mind
Sc3-e4-a1 or Sc3-d5-a1 (2021-06-27)
A.Buchanan: A "left-knight" on c3 can move to a2,b5,e4,d1. These look as if they are just scattered, but in fact they are on a straight line with gradient 1/2. It runs from c3 - e4 -b5 - d1 - a2 and back to c3. Similarly the "right-knight" defines an orthogonal line with gradient 2: c3 - d5 etc. A whole knight makes a move on one of these lines, just like a rook makes a move on a file *or* a rank. It's then obvious that the knight can access any square in 2 moves. The catch is that while a rook can be blocked on a line by two pieces (*two* needed because it's a cycle), a knight accesses all the points as a leaper: it's not actually riding *along* the line, it's just mimicking that effect. So it's unblockable. The "stars are right" for this trick only when the torus is 5x5. (2021-06-28)
A.Buchanan: I think this space has 25*24*20 = 12,000 symmetries. Map a1 anywhere (25), then map a2 anywhere else (24), then map b1 anywhere but the 5 points on the line containing a1 & a2 (20). So it's "doubly transitive" on directions - this means any of these 15 piece types can be mapped to any other. (2021-06-28)
Henrik Juel: Your enlightenment is appreciated, Andrew (2021-06-28)
comment
Keywords: Torus (5x5), no 8x8 board
Genre: Fairies, Mathematics
FEN: qqqqqqqq/qqqqqqqq/q5qq/q5qq/q1BNR1qq/q5qq/q5qq/qqqqqqqq
Input: A.Buchanan, 2021-06-27
Last update: A.Buchanan, 2021-06-27 more...
83 - P1394190
Andrew Buchanan
1 Problemas 36, p. 1182, 10/2021
after Tivadar Kardos and Jozsef Bajtay
P1394190
(15+6) C+
s#2*
* 1. ... Sxc1/Sxc3/Sxb4 2. Txc1/Txc3/Dxb4 Lxg7#
1. cxd6ep+ Sxc3 2. d7 Lxg7#
play all play one stop play next play all
corrects P1007465 from 65 years before.
Henrik Juel: set play 1... Sxc1/Sxc3/Sxb4 2.Txc1/Txc3/Dxb4 Lxg7#
solution 1.cxd6ep+ Sxc3 2.d7 Lxg7#
Last move was not c4xd3 or e4xd3 (on a light square), because the missing white man is the dark-squared [Lc1], so it was d7-d5, legitimizing the ep key (2021-10-03)
A.Buchanan: Sound + lighter + W2 becomes sole viable tempo move (with 10 other White pieces able to move). (2021-10-04)
comment
Keywords: En passant as key, Grab, Tempo Move
Genre: s#, Retro
Computer test: HC+ Popeye v4.87 & simple retro-thinking
FEN: 7b/1p4P1/1Pk1P3/PNPpKB2/QP1P1P2/2Rp4/n2N4/2R5
Input: A.Buchanan, 2021-10-03
Last update: A.Buchanan, 2021-10-13 more...
84 - P1394373
Michel Caillaud
Andrew Buchanan

MatPlus.net Forum 29-08-2021
P1394373
(14+14) C+
PG in a) 7.0 b) 7.5
Staugaard castling
a) 1. e4 f5 2. e5 Sf6 3. exf6 Kf7 4. fxe7 Kf6 5. e8=T La3 6. 0-0-0-0-0-0 Lxb2 7. Kd3 Lxa1
b) 1. e4 f5 2. e5 Sf6 3. exf6 Kf7 4. fxe7 Kf6 5. e8=T La3 6. Ke2 Lxb2 7. Kd3 Lxa1 8. Te2
play all play one stop play next play all
Engine shows orthodox solution in 7.5 and nothing shorter. Staugaard implies at least 7 White moves of which 2 are captures to promote on d8. So Black needs 7 moves. sL only released after W5 promotion, so last 3 Black moves are with bishop. If 7.0 moves exactly, then can use engine for first 5.0, which has unique solution. If 7.5, then White must lose a tempo. b2-b4 is too late, so must be with wK. But cannot triangulate via e4 or d4 because of checks. So no Staugaard castling in 7.5.
Henrik Juel: Part b) is an orthodox proof game, which is C+ Euclide 1.01
The solution is
1. Be2-e4 Bf7-f5 2. Be4-e5 Sg8-f6 3. Be5xf6 Ke8-f7
4. Bf6xe7 Kf7-f6 5. Be7-e8=T Lf8-a3 6. Ke1-e2 La3xb2
7. Ke2-d3 Lb2xa1 8. Te8-e2
In part a) you can save a white move by Staugaard castling
1.-5. as above, then 6. 0-0-0-0-0-0 Lxb2 7. Ke3-d3 Lxa1
Note that after this castling you cannot reach 7.5 moves by going Ke3-e4-d3 or Ke3-Kc4-d3, so part b) is also correct as a fairy proof game (2021-10-05)
Henrik Juel: Trying to waste a white move early in part b) also fails
1.e3? f5 2.e4 Sg6 3.e5 Kf7 4.exf6 Kf6??
because Black cannot make his 4th move (2021-10-05)
Henrik Juel: 2... Sg6 should be Sf6, of course (2021-10-05)
comment
Keywords: Unique Proof Game, Staugaard castling, Promotion (T), Prenix (T)
Genre: Retro, Fairies
Computer test: a) HC+ Popeye v4.87 for first 5.0 + reasoning: see Solution Text b) C+ Popeye v4.87 in 7.5 and and not shorter
FEN: rnbq3r/pppp2pp/5k2/5p2/8/3K4/P1PPRPPP/bNBQ1BNR
Input: A.Buchanan, 2021-10-04
Last update: A.Buchanan, 2021-10-06 more...
85 - P1394484
Andrew Buchanan
A The Problemist Supplement 174, p. 182, 09/2021
Motto="U for Uplex"
P1394484
(4+3) C+
h#2.5 Duplex
w) 1. a2 a6 2. Ka3 Ta5#
s) 1. b2 Td5 2. b1=D Td3 3. Db2#
play all play one stop play next play all
BTM in both twins.
Numerous retro tries but none distinct in the retro twin w).
AB: Duplex means that there is a twin where B/W roles are reversed. If we can deduce who must have the move then, e.g. in a helpmate, one of those twins will lose the first single move. So here it's Black to move, and the twins are BWBWB# (Black checkmating White) and BWBW# (White checkmating Black). "Uplex" is not a Fairy Condition - it's just an identifier of an obvious idea for retro-active compositions, which curiously hasn't been explored before, as far as Geoff Foster and I can see.
Henrik Juel: Thanks for the explanation, Andrew
Here Black has no last move, so he has the move
1.b2 Td5 2.b1=D Td3 3.Db2#
1.a2 a6 2.Ka3 Ta5#
C+ Popeye 4.61 (using 'sti h#2.5 opt hal' and 'sti h#2') (2021-10-09)
comment
Keywords: No legal last move for Black, Miniature, Character problem (U)
Genre: h#, Retro
Computer test: HC+ Last move analysis + Popeye 4.61
FEN: 8/8/8/P1R5/k1P5/ppK5/8/8
Input: A.Buchanan, 2021-10-08
Last update: A.Buchanan, 2023-12-06 more...
86 - P1394485
Andrew Buchanan
B The Problemist Supplement 174, p. 182, 09/2021
P1394485
(16+15) C+
h#2.5 Duplex
w) 1. Se6 Sd5 2. Sd8 Sxc7#
s) 1. Sxd1 Kxd1 2. Se4 Se1 3. Sxf2#
play all play one stop play next play all
BTM in both twins.
Numerous retro tries but none distinct in the retro twin w).
Henrik Juel: The total number of white moves in any proof game is even, and the number of black move is odd
The different parities imply that White made the last move, so it is Black to move
1.Sxd1 Kxd1 2.Se4 Se1 3.Sxf#
1.Se6 Sd5 2.Sd8 Sxc7#
C+ Popeye 4.61 (2021-10-09)
comment
Keywords: No legal last move for Black, Parity Argument
Genre: h#, Retro
Computer test: HC+ Parity counting + Popeye 4.61
FEN: r1b1kb1r/pppppppp/8/2n5/8/2nNN3/PPPPPPPP/R1BQKB1R
Input: A.Buchanan, 2021-10-08
Last update: A.Buchanan, 2023-12-06 more...
87 - P1394486
Geoff Foster
Andrew Buchanan

C The Problemist Supplement 174, p. 182, 09/2021
P1394486
(16+16) C+
h#2.5 Duplex
w) 1. e5 Sxg7+ 2. Ke7 Sd5#
s) 1. g6 d3 2. Lh6 Kd2 3. Sf3#
play all play one stop play next play all
BTM in both twins
Numerous retro tries but none distinct in the retro twin w).
Henrik Juel: A parity argument shows that it is Black to move
1.g6 d3 2.Lh6 Kd2 3.Sf3#
1.e5 Sxg7# 2.Ke7 Sd5#
C+ Popeye 4.61 (2021-10-09)
comment
Keywords: No legal last move for Black, Parity Argument, Capture-free
Genre: h#, Retro
Computer test: HC+ Parity counting + Popeye 4.61
FEN: r1bqkb1r/pppppppp/3n4/6nN/8/2N5/PPPPPPPP/R1BQKB1R
Input: A.Buchanan, 2021-10-08
Last update: A.Buchanan, 2023-12-06 more...
88 - P1394487
Andrew Buchanan
D The Problemist Supplement 174, p. 182, 09/2021
P1394487
(15+15) C+
h#3 Duplex
w) 1. Sb4 Sg5 2. Sc6 Se6 3. Sd8 Sxc7#
s) 1. Sb4 Sf3 2. Sd3 Se1 3. Sxf2#
play all play one stop play next play all
BTM in both twins
Numerous retro tries but none distinct in the retro twin s).
Henrik Juel: A parity argument shows that it White to move
Popeye 4.61 found lots of solutions with 'sti h#3 opt hal' and none with 'sti h#2.5' (2021-10-09)
Henrik Juel: Here are the correct details of the parity argument
White has made an odd number of moves (K odd, TT odd, SS even, P odd)
Black has mad an even number of moves (K even, TT even, SS even, PP even)
So White made last move, and it is Black to move
1.Sb4 Sg5 2.Sc6 Se6 3.Sd8 Sxc7# (White mates, 'h#3')
1.Sb4 Sf3 2.Sd3 Se1 3.Sxf2# (Black mates, 'h#2.5 opt hal')
C+ Popeye 4.61 (2021-10-09)
comment
Keywords: No legal last move for Black, Parity Argument
Genre: h#, Retro
Computer test: HC+ Parity counting + Popeye 4.61
FEN: 2b1kbrn/rppppppN/p6p/8/8/P7/nPPPPPPP/1RBK1BNR
Input: A.Buchanan, 2021-10-08
Last update: A.Buchanan, 2023-12-06 more...
89 - P1394490
Ayrton Twigg
Andrew Buchanan

Discord Chess Problems & Studies Server 10/05/2021
P1394490
(4+3) C+
h#4
1. La4 Lh7 2. Ld1 Tg6 3. Ke4 e3 4. Lf3 Te6#
play all play one stop play next play all
Henrik Juel: C+ Popeye 4.61
1.La4 Lh7 2.Ld1 Tg6 3.Ke4 e3 4.Lf3 Te6#
Very nice (2021-10-09)
comment
Keywords: Miniature, Tempo Move (l), Indian, Model mate
Genre: h#
Computer test: C+ Popeye 4.61
FEN: K7/8/4R3/3p4/5k2/1b6/4P3/1B6
Input: A.Buchanan, 2021-10-09
Last update: A.Buchanan, 2023-05-08 more...
90 - P1394496
Vladimir Archakov
Andrew Buchanan

PDB Website 10/10/2021
VA, correction AB
P1394496
(15+3) C+
#2*
Set Play
1. ... Kxh1 2. Kf2#
1. ... Kxh3 2. Sf4#
1. ... Kxf3 2. Lb7#
BTM
1. ... hxg5 2. Sc3
2. ... Kxh1 3. Kf2#
2. ... Kxh3 3. Lf1#
2. ... Kxf3 3. 0-0#
play all play one stop play next play all
Corrects P0000914.
Black to move.
Missing White unit captured on h-file. So wPa promoted, hence 11 necessary captures by White, within budget.
more ...
comment
Keywords: No legal last move for Black, Mutate (2), Castling (wk)
Genre: 2#, Retro
Computer test: Henrik Juel: C+ Popeye 4.61 (2021-10-10)
FEN: 8/6PR/B6p/6BP/3P2Np/5P1P/3PN1kP/Q3K2R
Input: A.Buchanan, 2021-10-10
Last update: A.Buchanan, 2023-08-15 more...
91 - P1394553
William Geary
Andrew Buchanan

Discord Chess Problems & Studies Server 12/10/2021
WG, version AB
P1394553
(12+1) C+
#2
1. Sd6! zz
1. ... Ke5 2. Lc3#
1. ... Kxd6 2. Sge4#
1. ... Kc5 2. Le3#
1. ... Kd4 2. Sf3#
play all play one stop play next play all
Version of P1022259.
more ...
comment
Keywords: Plus flights, Rex solus (s)
Genre: 2#
Computer test: C+ Popeye 4.61
FEN: 3K4/3B1P2/4P3/3k2NR/4N3/P5P1/3BP3/3R4
Input: A.Buchanan, 2021-10-13
Last update: A.Buchanan, 2022-06-08 more...
92 - P1394733
Andrew Buchanan
PDB Website 19/10/2021
to Tivadar "of Thorn" Kardos
P1394733
(13+12) C+
BP in 6,0
1. Sf3 e5 2. Sxe5 Dg5 3. Sc6 Dxd2+ 4. Dxd2 Sf6 5. Dxd7+ Sfxd7 6. Sxb8 Sxb8
play all play one stop play next play all
Suggested by P0000541. If Tivadar's problem had been a double homebase, it would have been the first in the world, pipping by 8 months P0002288, Andrey Frolkin's rendering of E.C.Mortimer.
See also: https://gatherer.wizards.com/pages/card/details.aspx?name=Tivadar%20of%20Thorn
The flavour text suggests the impostor theme: "His blade came down upon the neck of a goblin — but not the one he had charged. When Tivadar looked up, the world he had known was gone."
Since the beginning in 1993, Magic the Gathering has had white and black knights as a kind of homage to chess. These creatures have evolved and Tivadar of Thorn is literally a white knight, who in chess terms we see charging out from g1. There are two main kinds of white knight: the anti-black and the anti-red, and Tivadar is the latter.
YM: Sorry - two impostors were in P1329742 (2021-10-20)
A.Buchanan: Is there a mode for viewing PDB problems where one doesn't get to see the keywords (or the solution, which also a bit of a hint)? (2021-10-20)
A.Buchanan: Yes, YM, your P1329742 is very good. And single impostor in homebase:2 is demonstrated in PG in 4.0. I wanted to post this one because I was surprised to render the problem sound just by j'adoubing one unit to its home square! There's also an interesting artistic cross-over with Magic the Gathering. (2021-10-21)
more ...
comment
Keywords: Unique Proof Game, Homebase (2), Impostor (s), Quasi-symmetrical position
Genre: Retro
Computer test: C+ Euclide 1.01
FEN: rnb1kb1r/ppp2ppp/8/8/8/8/PPP1PPPP/RNB1KB1R
Input: A.Buchanan, 2021-10-20
Last update: A.Buchanan, 2021-10-24 more...
93 - P1394836
Andrew Buchanan
ChessBase India 21/10/2021
after Georges Glaeser
P1394836
(15+15) C+
h#2.5 (who?) b) bK->d8
a) WTM 1. ... Sc3 Sc6 2. Sxd5 Sd8 3. Sxc7#
b) BTM 1. Sc6 2. Sc3 Sxd4 3. Sd1 Sxc2#
play all play one stop play next play all
See P0005272
more ...
comment
Keywords: Parity Argument, Symmetrical position (2), Asymmetrical solution (2), Whose move?
Genre: h#, Retro
Computer test: HC+ Popeye v4.87 & trivial retro-logic
FEN: r1b1kb1r/pppppppp/8/3nn3/3NN3/8/PPPPPPPP/R1B1KB1R
Reprints: Facebook 21/10/2021
Input: A.Buchanan, 2021-10-23
Last update: A.Buchanan, 2022-02-16 more...
94 - P1396159
Tivadar Kardos
James Malcom
Andrew Buchanan

PDB Website 24/11/2021
TK, correction JM & AB
P1396159
(6+15) C+
h#3
1. dxe3ep+ Kxc4 2. Lc3 Sxc2 3. Ta5 axb3#
R: 1. e2-e4 Tf3-d3+ 2. Ke4-d5
play all play one stop play next play all
See P0003211

Example Proof Game: 1. b3 a5 2. c4 a4 3. Na3 b5 4. d4 c5 5. Bg5 h6 6. f4 hxg5 7. Nf3 gxf4 8. Qd3 bxc4 9. Nc2 axb3 10. Rc1 Bb7 11. Na1 Nf6 12. Rc3 Nh5 13. Qe3 fxe3 14. Nd2 exd2+ 15. Kf2 Nf4 16. Rg1 Nh3+ 17. gxh3 Bh1 18. Rcg3 Ra6 19. Rg6 Rf6+ 20. Ke3 Rh5 21. Bg2 Nc6 22. Be4 Na5 23. Bc2 bxc2 24. R1g4 Rf3+ 25. Ke4 Nb3 26. Rd6 exd6 27. Rf4 Qh4 28. Rg4 Qe1 29. Rf4 Kd8 30. Rg4 Kc7 31. Rf4 Kb6 32. Rg4 Ka5 33. Rf4 Ka4 34. Rg4 Rhf5 35. Rh4 g5 36. Rg4 Bg7 37. Rh4 Be5 38. Rf4 cxd4 39. Rg4 f6 40. Rh4 Qf1 41. Rf4 gxf4 42. Kd5 Rd3+ 43. e4
Henrik Juel: Black pawns captured all 10 missing white men, and White captured g2xSh3
Last move was not e3-e4 (because of the check from Lh1), but e2-e4
HC+ Popeye 4.61 (2021-11-24)
A.Buchanan: I’d like to claim that Popeye + Retractor + example proof game means this problem is C+. If not, what more would be required. (2021-11-24)
Henrik Juel: I guess that suffices (2021-11-24)
comment
Keywords: En passant as key, Checking key
Genre: h#, Retro
Computer test: C+ Popeye 4.61 for forward play Retractor 2.0 for retraction Lichess to check demo game
FEN: 8/3p4/3p1p2/3Kbr2/k1ppPp2/1n1r3P/P1pp3P/N4q1b
Input: James Malcom, 2021-11-24
Last update: A.Buchanan, 2023-07-13 more...
95 - P1396163
Tivadar Kardos
Andrew Buchanan

PDB Website 24/11/2021
TK, correction AB
P1396163
(8+14) C+
h#3
1. cxb3ep+ Sb4+ 2. Kb1 Sxe2 3. b2 0-0#
R: 1. b2-b4 Tc3-a3+ 2. Sa3-c2
play all play one stop play next play all
Black captured 8 white men with pawns. Critically sBd & sBe never captured, therefore White pawns captured onto d- & e-files (to explain the pawn inversions there). Therefore wBb4 did not come from c3.
See P0574383.

With the ink still wet on this correction, I would like to remove sD. Sound by Popeye & Retractor, but needs an adapted proof game for C+.

Proof Game: 1. c4 a6 2. g3 Nc6 3. Bg2 Na5 4. Bc6 h5 5. Bb5 axb5 6. g4 c5 7. d4 cxd4 8. e4 f5 9. Be3 fxe4 10. f4 g5 11. Qf3 Nb3 12. Na3 hxg4 13. Nc2 gxf3 14. Rd1 Na1 15. Rd2 Ra3 16. Rg2 Rc3 17. a4 d3 18. Bf2 e3 19. Bg3 e5 20. Re2 e4 21. a5 d5 22. a6 d4 23. a7 Qd5 24. a8=R Qe5 25. Rf2 Kd7 26. Re2 Nf6 27. Rd2 Nd5 28. cxd5 Kd6 29. Rf2 Kc5 30. Re2 b6 31. Rd2 Kc4 32. fxe5 Kb3 33. Re2 fxe2 34. Rb8 Bg4 35. Rb7 Bf3 36. Rc7 Ka2 37. Bf4 gxf4 38. Rc6 Bb4 39. Rc5 Rh3 40. Na3 Ba5 41. Rc4 bxc4 42. Nc2 Ra3+ 43. b4
A.Buchanan: 6n1/8/1q6/b7/1Ppppp2/r2ppp1r/k1N1p2P/n3K1NR has one less piece again, but I prefer the current version as retro logic is more interesting. (2021-11-26)
James Malcom: Enjoy an optimal PG Andrew. The total sum of the queen & knight journeys is 8 no matter which knight ends up on a1. (2021-11-27)
A.Buchanan: :-) thanks James (2021-11-27)
more ...
comment
Keywords: En passant as key, Castling (wk)
Genre: h#, Retro
Computer test: C+ Popeye 4.61, Retractor 2.0 & example proof game.
FEN: 8/8/1p6/b2PP3/1Ppppp2/r2ppb1r/k1N1p2P/n3K1NR
Input: A.Buchanan, 2021-11-24
Last update: A.Buchanan, 2023-08-15 more...
96 - P1396199
Tivadar Kardos
Andrew Buchanan

PDB Website 25/11/2021
TK, version AB
P1396199
(10+13) C+
PG in 8.5
1. Sc3 Sf6 2. Se4 Sxe4 3. g3 Sxg3 4. Sf3 Sxh1 5. Se5 Sxf2 6. Sxd7 Sxd1 7. Sxb8 Txb8 8. Kxd1 Ta8 9. Ke1
play all play one stop play next play all
P0000736 plus the 1.5 obvious moves. Why did he stop? :-)
Henrik Juel: He probably stopped because
1. he was afraid of cooks
2. the Homebase theme was unknown in 1979
Is the extension to 8.5 C+? (2021-11-25)
Olaf Jenkner: This version is in my opinion 100 times better than P0000736, a homebase with 9 missing men in only 8.5 moves.
Is there a record list of proof games "homebase with x missung men" in a minimum number of moves? (2021-11-25)
A.Buchanan: Thanks Olaf for your kind words. I don't think there is such a list. PDB has today 19 homebase unique PGs which are no longer than this with no fewer captures. Most are 9 captures but P1000453 by Le Gleuher alone manages to get a 10th capture. He also manages the shortest (6.5 moves P1000944), with 7.5 moves by Mintz P1329742 as runner-up, and 4 others in 8.0. To be fair, the aesthetic for the Future Proof Game gang has generally been to *minimize* the number of captures. Except for Mintz and one other, all involve promotions. (2021-11-26)
more ...
comment
Keywords: Unique Proof Game, Homebase (2), Switchback (Kt)
Genre: Retro
Computer test: C+ Natch 3.1 in 53 minutes
FEN: r1bqkb1r/ppp1pppp/8/8/8/8/PPPPP2P/R1B1KB2
Input: A.Buchanan, 2021-11-25
Last update: A.Buchanan, 2021-11-26 more...
97 - P1396304
Tivadar Kardos
Andrew Buchanan

PDB Website 27/11/2021
Happy Birthday to James Malcom!
A gift from Tivadar Kardos (helped a little by Andrew Buchanan)
I don't think this one needs a proof game :)
TK, version AB
P1396304
(11+13) C+
h#3
2 solutions
1. Lxa2 Txa2 2. 0-0-0 Txa7 3. Td7 Ta8#
1. Dg3 Txb1 2. Dxb3 Txb3 3. 0-0 Tg3#
1. Lxa2 0-0-0? 2. Dxg2 Tg1 3. 0-0 Txg2# (White can't castle)
play all play one stop play next play all
The cooked P0006972 can be fixed many ways. I wanted to find a single touch that would keep the intended solution, the intended try, and exactly one of the cooks which seemed worth saving, while eliminating all the other cooks.
Henrik Juel: Black captured [Lf1] and the remaining 4 missing white men with exdxcxTb2-b1=L and gxh
1.Bb1*a2 Ra1*a2 2.0-0-0 Ra2*a7 3.Rd8-d7 Ra7-a8 #
1.Qg8-g3 Ra1*b1 2.Qg3*b3 Rb1*b3 3.0-0 Rb3-g3 #
Not 1.Bb1*a2 0-0-0? 2.Qg8*g2 Rd1-g1 3.0-0 Rg1*g2 # (White may not castle, as he has moved his king)
Neat birthday greeting (2021-11-27)
James Malcom: Thanks for the warm gift Andrew. Huzzah! (2021-11-28)
comment
Keywords: Castling (sgsk), Cant Castler (wg), Obvious promotion (l)
Genre: h#, Retro
Computer test: HC+ Popeye v4.87 + trivial retro-logic
FEN: r3k1qr/pp3p1p/1bp5/3pB2p/8/1P6/P1PPPPPP/Rb2K3
Input: A.Buchanan, 2021-11-27
Last update: A.Buchanan, 2021-11-28 more...
98 - P1396401
Laszlo Lindner
Jozsef Bajtay
Tivadar Kardos
Andrew Buchanan

Discord Chess Problems & Studies Server 29/11/2021
LL,JB,TK, correction AB
P1396401
(6+15) C+
h#3
1. axb3ep a3 2. Sa2 Kxg4 3. Sc3 d3#
play all play one stop play next play all
AB: The en passant is pure tempo. *All* other moves interfere with the solution. After first clearing a2 with 1. ... a3, White's second move is also pure tempo. sDf2 is a "value weasel" - the problem would still be sound with sB, but it's entertaining that sD cannot move to any of 9 apparently available squares.
Corrects P0574612.
A.Buchanan: All I have done is fix a bug. Apart from applause at the motive for B1 & W2, also note the way all pieces are necessary for for unique forward play: there is zero "retro-dressing" (2021-11-29)
Henrik Juel: White has captured once only, so last move was not a3xb4 or c3xb4, but b2-b4, legitimizing the ep key (2021-11-29)
more ...
comment
Keywords: En passant as key, Tempo Move (sw)
Genre: h#, Retro
Computer test: HC+ Popeye v4.87 & Retractor 2.1.1 Human contribution is "position prior to retractions looks legal enough."
FEN: 8/7p/5p1P/1ppb2pK/pPkn2r1/8/P1PPpq2/2n1br2
Input: A.Buchanan, 2021-11-29
Last update: A.Buchanan, 2021-11-29 more...
99 - P1397613
Tivadar Kardos
Andrew Buchanan

PDB Website 31/12/2021
TK, correction AB
P1397613
(6+4) C+
hs#4
1. d4 Td2 2. Lc3 Lc1 3. d5+ e5+ 4. dxe6ep+ Td4#
play all play one stop play next play all
Fixes cook in P1303210, and improves economy & precision
more ...
comment
Keywords: En passant
Genre: Fairies
Computer test: C+, Gustav 4.2a, Brute Force
FEN: 4R3/4p3/5k2/8/5K2/b4PR1/1r1P4/B7
Input: A.Buchanan, 2021-12-31
Last update: James Malcom, 2022-01-02 more...
100 - P1398014
Tivadar Kardos
Andrew Buchanan

PDB Website 08/01/2022
TK, correction AB
P1398014
(6+16) C+
h#3
1. bxc3ep+ d3 2. 0-0 Tf4 3. Kh8 Txf8#
play all play one stop play next play all
Not R: 1. c3-c4? La6xb5? because Black's 10 captures are already accounted for: 6 pawn captures on files a-d, e.g.: bax, cxbxa, dxcxbxa + 4 waylaid pawns on files e-h or maybe 2 more pawn captures if bPe & bPf cross-capture.
Corrected version of P0003264, with extra tightness.
more ...
comment
Keywords: En passant as key, Castling (sk)
Genre: h#, Retro
Computer test: HC+ Popeye 4.61
FEN: N3k2r/6pp/1pn5/Pb2p3/RpP5/pr2qp2/p2P2n1/5Kb1
Input: A.Buchanan, 2022-01-07
Last update: A.Buchanan, 2022-03-20 more...
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