No.762 
Geoff Foster
(Australia)

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Original Problems, Julia’s Fairies – 2015 (I): January – June

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No.762 by Geoff Foster –  Inverted echo mates with opposite fairy conditions (Back-To-Back & Face-To-Face) in two twins! (JV)


Definition:

Back-To-Back: When pieces of opposite colors stand back-to-back with each other on the same file (white piece is on the top of black!), they exchange their roles. A pawn on the first rank cannot move. Any piece can make an en passant capture when it has got a role of Pawn by Back-To-Back.

Face-To-Face: When pieces of opposite colors stand face-to-face with each other on the same file (black piece is on the top of white!), they exchange their roles. A pawn on the first rank cannot move. Any piece can make an en passant capture when it has got a role of Pawn by Face-To-Face.


No.762 Geoff Foster
Australia

original – 28.03.2015

Solutions: (click to show/hide)

Black Ke3 Neutral Qf7 Sf8

h#2,5                                (0+1+2)
Back-To-Back
b) Face-To-Face
(no white King)


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Kjell Widlert
Kjell Widlert
March 28, 2015 22:43

Illustrates the fact that BTB is just like FTF, only upside down!
By the way, a wonderful mate where Black cannot save himself by moving away the NQ.

S K Balasubramanian
S K Balasubramanian
March 29, 2015 07:17

The beauty is that the nS is virtually pinned in both the phases and cannot move. If it moves the nQ gets its original power. The other important effect is that the bK cannot capture the unsupported checking piece due to self check — in (a) due to BTB effect and in (b) due to FTF effect. Wondeful!

Nikola Predrag
Nikola Predrag
March 29, 2015 07:47

nS is not pinned. b1/c2 in a) and e2/f3 in b) are guarded only by white power of nQ.
White uses in both mates only the Q-power of both neutrals for double Queen-checks.
And Black might use only the S-power of both Neutrals but has no legal move 🙂

S K Balasubramanian
S K Balasubramanian
March 31, 2015 05:42

Thank you Nikola, I didn’t notice it. Many times I get confused with neutral pieces.

Nikola Predrag
Nikola Predrag
April 1, 2015 00:57

I am also confused about that.
So I try to remember that in a neutral BTB pair, there are 2 white pieces which may move like the lower piece, or 2 black pieces moving like the upper piece.
It’s an opposite case in a FTF pair, but still it’s tricky.

Here are two original examples for the exercise:
—————-
Pieces Neutral Kd7 Ph6 Pe4
Stipulation h=3.5; Condition BackToBack
1…nPh7 2.nKe6 nPh8=nQ 3.nQe5+ nKa6 4.nPd5 nQd4=
—————–
Pieces Neutral Kd5 Rc4 Pc2
Stipulation h=3.5; Condition ChameleonChess+BackToBack
1…nRc3=nQ 2.nKc4+ nKf1 3.nPg2+ nPg4 4.nKg1 nQg3=nS=