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is it just me? but my head hurts trying to understand this

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Hi

Trust Ruxton to drop that one in your lap in a thread with tactics in the title.

First of all I'll lay it out correctly, I hate sloppy lay outs, there is no need for it.

I went to all that trouble to write the code to give you FEN's and PGN's (Posting Geoff's Notation.)

and you guys never use it.

(Keith you know better than to give these guys a position to set up in their head,

even a simple one like this. And puzzles like this are never going to be popular because

they cannot switch on the Fritz to solve it for them......though no doubt some have tried.)

Keith wrote:

"One of my favourite puzzles is a game where the normal rules of chess apply but there is

one additional rule:

No piece can move from a square of one colour to a square of a different colour

(so knights can never move, bishops work as normal etc.)

The position is a black king on e8, white king on e1, white pawns on f2 and d2 and a white bishop

carelessly placed between e3 and e4.

The question is: which square does the bishop stand on, e3 or e4?

[pos]4k3/8/8/8/8/4B3/3P1P2/4K3 b - - 0 26[/pos] [pos]4k3/8/8/8/4B3/8/3P1P2/4K3 b - - 0 1[/pos]

So given the conditions as stated above, which diagram is correct?

As stated it must Be3. What took the last Black dark squared piece?

It cannot have been the White pawns or the White King, it must have been the dark squared Bishop.

Someone said;

"So, you can see very readily that it would be impossible to reconstruct every move of the game

- known as a proof game."

Took me all of two minutes and is the clumiest piece of retro you will ever see.

But given time I reckon I can shave off 5-6 moves, maybe more. But it can be done.

The problem is sound.

[pgn]1. g4 g5 2. Bg2 Bg7 3. Bxb7 Bxb2 4. Bxa8 Bxa1 5. Ba3 Ba6 6. Bxe7 Bxe2 7.

Bxd8 Bxd1 8. Bxc7 Bxc2 9. Bxb8 Bxb1 10. Bxa7 Bxa2 11. Be4 Be6 12. Bxh7 Bxg4

13. h4 Bf6 14. hxg5 Bxg5 15. Bxg8 Bf4 16. Rh7 Bh2 17. Rxf7 Bxg1 18. Rxd7

Bxd7 19. Bd4 Be6 20. Bxh8 Bf7 21. Bxf7+ Kxf7 22. Bd4 Ke8 23. Ba7 Bh2 24.

Bb6 Bf4 25. Bc5 Be3 26. Bxe3[/pgn]*

Over on Red Hot Pawn I'm in a problem club run by a Retro King - I'll see if he is

interested in knocking the proof game down to under 20 moves.

Andy why does the PGN thingy thing start automatically moving right away.

By the time they read as far down as the PGN the game is half over and the

reader has to re-set it. This is sloppy.

Tweak it so the reader can start the PGN off when he is good and ready.

I can see I'm going to have make a regular visits here. You lot have become sloppy.

BTW my plastic Duck is now in New York and has even visited the Marshall Chess Club.

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Now that we've got the bishop onto the correct square (e3). Lets set a different puzzle with the same rules.

Move the white king onto d1.

White to play and stalemate in the minimum number of moves - with black's full cooperation.

On which square is black's king when stalemated?

No moving pieces now- think ahead

Posts: 144

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Joined: Aug 2011

Now that we've got the bishop onto the correct square (e3).

Let us set a different puzzle with the same rules.

Move the White King to d1.

[pos]4k3/8/8/8/8/4B3/3P1P2/3K4 w - - 0 1[/pos]

White to play and stalemate in the minimum number of moves - with Black's full cooperation.

On which square is Black's King when stalemated?

No moving pieces now- think ahead.

Posted by Phil Thomas.

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Geoff Chandler Wrote:Now that we've got the bishop onto the correct square (e3).

Let us set a different puzzle with the same rules.

White to play and stalemate in the minimum number of moves - with Black's full cooperation.

On which square is Black's King when stalemated?

No moving pieces now- think ahead.

Posted by Phil Thomas.

I guess 4 moves... with black's king stalemated on h5?

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That lad from Red Hot Pawn improved someaht on my lazy effort.

His is 21 moves.

[pgn]1. b4 d5 2. Bb2 Bh3 3. Bxg7 Bxg2 4. Bxh8 e5 5. Bxe5 Bxh1 6. Bxc7 Qg5 7. Bxb8

Qxg1 8. Bxa7 Qxh2 9. e4 Bxe4 10. Bg2 Bxc2 11. Bxd5 Bxb1 12. Bxb7 Bxa2 13. Qb1

Bxb1 14. Bxa8 Be4 15. Bxe4 Qh6 16. Bxh7 Bxb4 17. Bxg8 Ba3 18. Bxf7+ Kxf7 19.

Rxa3 Ke8 20. Re3+ Qxe3+ 21. Bxe3[/pgn]

He is Swissgambit on RHP but in problem circles his real name is quite well known.

Not at liberty to reveal his true ID.

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[pos]7k/8/8/8/8/8/8/K7[/pos]

With just bare kings as above white to move can force stalemate in 5 moves - Black's only real choice is which of 5 squares to be on at the end.

But with black to move (unless I've missed something) even with White's help Black can not deliver stalemate.

Can anyone explain why ?

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The king which moves first can deliver stalemate (with help, of course) but can never be stalemated.

Just as in normal chess a knight that starts on a white square can reach other white squares only in an even number of moves and can reach black squares only in an odd number of moves, so in this form of chess a king can reach certain squares only in an even number of moves and others only in an odd number of moves.

A king starting on a1 can reach a1, a3, a5, a7, c1, c3, c5, c7, e1, e3, e5, e7, g1, g3, g5 and g7 in an even number of moves, and b2, b4, b6, b8, d2, d4, d6, d8, f2, f4, f6, f8, h2, h4, h6 and h8 in an odd number of moves. A king starting on h8 reaches the first set of squares in an odd and the second in an even number of moves.

In all cases, the square on which a king can be stalemated is the same quality (either odd or even) of distance away for that king as the square on which the stalemating king must land - but for the latter king both squares have the opposite quality. So if the king which is to be stalemated arrives at its destination in an even number of moves, the other king must arrive in the stalemating square in an odd number of moves. And so the king which moves first can never be stalemated, because the opposing king cannot arrive at the stalemating square in the same number of moves -it needs one more move.

Simple!

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Hi

That lad, Swissgambit sent me this. It's a retro puzzle.

You have to recreate the exact position from the initial set up.

Normal chess rules.

[pos]r2qk1nr/pp2pppp/1pp5/8/8/6P1/PPPP2PP/R2QK1NR w KQkq - 0 1[/pos]

There is a White Pawn on f4 or f5. Which square is it on?.