I just don't see the challenge in Remellion's #104.
Bring the bishop to h3 via d3-c5, then play ...f5, bring the other bishop to c5 and suicide the rooks. There is plenty of place to maneuver...
Is this position legal?
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lixinzheng wrote: (about #104)
#1 is not legal because the bishop would have to maneuver from the h3-c8 diagonal because white's pawn is on f3. There is no way to get a black rook out to sacrifice on f3 because to do that you would have to push f5 and then the bishop cannot get to h3...
You just do it in order. First you bring the bishop to h3, then you push f5, then you feed a pawn on f3.
@Remellion, since all of black's other peices are still on the board, black's two missing rooks mus have been sacrificed on f3 and h3/h4. However,
a) White's bishop must have gotten to h3 before one of f5 or g6 was played.
b)f5 and g6 need to be played before a black rook is released (g6 to clear the bishop)
c) A rook is needed to sacrifice itself on f3 before white can get the bishop to h3.
The only way to avoid the contradiction is if f5 and g6 are not played at all, but rather white sacrificed a rook and bishop to allow gxf6 and later fxg6. But then to get white's dark square bishop out for gxf6, white needs to play b3. So that's why the first position is illegal and the second is legal.
FancyKnight wrote:
@Remellion, since all of black's other peices are still on the board, black's two missing rooks mus have been sacrificed on f3 and h3/h4. However,
a) White's bishop must have gotten to h3 before one of f5 or g6 was played.
b)f5 and g6 need to be played before a black rook is released (g6 to clear the bishop)
c) A rook is needed to sacrifice itself on f3 before white can get the bishop to h3.
(...)
Oh, clever. Completely forgot about c), somehow.
FancyKnight got it right again! The sneaky cross-capture proves #104-2 is possible; also to note is that gxf6 must come before fxg6, since after fxg6 the pawns and f8-bishop would keep the rook trapped. Great job!
Currently working on another pair. No guarantees it'll hold up to scrutiny...
OK. This took a fair while to compose and isn't as interesting as I wanted it to be, but should be fairly cute. Again, two similar positions. [EDIT: EDIT EDIT: Graagh. Additional question: for each diagram, which of black's pieces must be original, i.e. unpromoted? Also, White to play and win in the first.]
Omg, 100+ posts in 4 days!
I'm not too good at these, but #117 seems illegal.
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Yeah 117 is illegal. There's nothing to capture the last piece after the Knights have mopped up.
#115 is still available, and here is also a simple corollary to #117:
This could be possible.
I'm unsure. White has just played bxa4 to remove the last Black Knight having earlier taken on b3. What I haven't figured out yet is whether Black can arrange for both of his Knights to arrive on b3 and a4 on consecutive moves, given that the Knights begin on opposite-coloured squares and must change the colour of their squares each move. In other words, it's a parity problem.
Gil-Gandel wrote:
I'm unsure. White has just played bxa4 to remove the last Black Knight having earlier taken on b3. What I haven't figured out yet is whether Black can arrange for both of his Knights to arrive on b3 and a4 on consecutive moves, given that the Knights begin on opposite-coloured squares and must change the colour of their squares each move. In other words, it's a parity problem.
Not a problem - you can lose time if you take the knights on the correct squares.
#115 is impossible; there is no way the bishop can get to a6.
Nice puzzles. There should be an excercise book for this. :P