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No.660 |
Original Problems, Julia’s Fairies – 2014 (III): September – December →Previous ; →Next ; →List 2014(III) Please send your original fairy problems to: julia@juliasfairies.com |
No.660 by Neal Turner – A long SAT-play of 4 pieces in 2 solutions! (JV)
Definitions:
SAT: A king is in check if any of its flight squares are unguarded by opposing pieces.
Grasshopper(G): Moves along Q-lines over another unit of either color to the square immediately beyond that unit. A capture may be made on arrival, but the hurdle is not affected.
Nightrider(N): (1,2) Rider. Operates along straight lines with squares lying a Knight`s move away from each other.
Royal piece: Piece that executes a function of the King on the board.
Pser: This is the original definition by its inventor, Dan Meinking: A parry series-mover differs from a standard series-mover prior to the last move as follows:
- the series-side may give check during the series;
- when checked, the idle-side must immediately parry the threat;
- a parry-move may be helpful or defensive, depending on the problem-type (for example – in Pser-s# the parry-move is defensive);
- after a check-and-parry, the series-side continues the series.
Every Pser problem combines two stipulations:
Part 1 – Pser, which indicates the special series play with participation of both sides according to the author’s definition;
Part 2 – the kind of problem, according to well known stipulations, which can show direct play (n#, n=, s#, s= r#, r=, etc), help play (h#, h=, h==, etc) or mixed play (hs#, hs=, hs= =, etc).
(For more explanations about Pser see IGM Petko A. Petkov article “The Wonderful (new genre) Parry Series“)
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No.660 Neal Turner |
Solutions: (click to show/hide) |
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White Ga1 Nd1
White Royal Gf3
Black Royal Gc8
pser-s#13 2 solutions (3+1) |
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SAT, as well as Vogtlaender, are difficult conditions to work with because, more or less, checks are reversed. The idea of working with Royal Grasshoppers in SAT is interesting because those units have limited moving possibilities – to check one of them, we must provide it a hurdle with legal jump, paying attention to the fact that the square after the reverse jump is guarded, otherwise the first jump would be a self-check!
For example in the first solution, the move 4…rGc4 is legal because square c6 is guarded by Gc1! The terminal move 13…rGe4# is not a self-check as squares c4 and g2 are guarded by the Na5, but is a checkmate because rGf3-d5 is a self-check!
Note that square c6 is not guarded before the putative move rGc4-c6, but only after. So maybe the definition used for SAT is a bit ambiguous. Generally speaking it is better, at least to my mind, to use the observation of a piece rather than the guarding of a square – the former presents no more risk of ambiguity.
We see the same phenomenon in the second solution: the move 5…rGg8 is legal because square e8 becomes guarded after the putative move rGg8-e8. Finally the mating move is highly specific too – 13…rGd5 is not a self-check as squares f7 and g2 are respectively guarded by Ga2 and Ne6, but is a checkmate as rGf3-c6 is a self-check…
I like much this problem (in fact I’m unable to understand how 2 such long series might be non-dualistic!), with only one small criticism – the check/parry is only used once in each solution.
PS to Julia: the definition of the Nightrider on the board is missing.
Thanks, Nicolas, the definition of Nightrider and the fairy pieces under the diagram are added. Sorry for the mistake!
Thanks Julia. I suggest the following equivalent (or am I wrong?) definition for the SAT condition, which seems to be clearer and without any possible ambiguity, as it involves only very basic features:
SAT: A King (or a Royal unit) is in check if it may legally move, in the orthodox sense.
This way the mating positions of Neal’s problem become very easy to understand, for example the second one:
– The Royal Gd5 is not in check (hence its previous move was legal) as its possible moves to f7 and g2 are both illegal (because of the next possibilities Ga2xGf7 and Ne6xGg2).
– The Royal Gd5 is giving check to the Royal Gf3 as this latter may legally move to square c6, in the orthodox sense. But this move rGf3-c6 is a self-check in the SAT sense as rGc6 may now legally move to e4, in the orthodox sense. Hence rGf3 is checkmated.
hm…. so in SAT a King is in check if it has flight square.
In the position
BKa2, BRb1b2, WRa3. is the black king is in check because it has two flights a3,b3? Can black avoid the check by moving to a1 where it has no flight squares?
Am I correct?
Sorry.. in that position black has just one flight square a3.
Yes, in your position the bK is in check as it may capture the wR. In fact the bK is obliged to move to square a1 – the only way to parry the check.
Thanks. Interesting ! So, black is stalemated, if his king in the centre of the board is surounded by 8 pawns and pieces (even though every one of the pieces/pawns can move in orthodox chess) ?
Exactly. All black pieces are pinned this way.
Then also any attack by opposite side on such square near king blocked by his own piece means in fact unpin of the piece in question. See e.g. try and key in #2 with some easy fairy pieces, unpinning threat pieces, or pendulum unpins in #23.
Yes. A very simple scheme involving a bK alone on the center of the board is: bKd5 wQc4f4. The bK is clearly not in SAT-check.
Among the 40 legal white moves, how many are checks/non-checks? Among the checking moves, how many are ckeckmates/non-checkmates? Among the non-checking moves, how many are stalemates/non-stalemates?
Answers: (37/3) (33/4) (1/2). The unique =1 move is Qc4-c8.