Illegal Position Contest!
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EvinSung wrote:
#5791
I would say this one is illegal, but would be legal if the h3 pawn were removed.
n9531l1 wrote:
Not if at least four black pawns have to promote on dark squares and all four white pawns have to reach files where they can promote on light squares.
Why do all four white pawns have to be promotable on light squares?
johntromp wrote:
n9531l1 wrote:
Not if at least four black pawns have to promote on dark squares and all four white pawns have to reach files where they can promote on light squares.
Why do all four white pawns have to be promotable on light squares?
What happened to the white pawns? The first two that captured the black rooks ended on dark-square-promotion files. Two were captured by black pawns which had to pass opposing pawns. The two on e6 and g6 would promote on light squares. The final two, which did promote, became light-squared bishops.
n9531l1 wrote:
What happened to the white pawns? The first two that captured the black rooks ended on dark-square-promotion files.
I don't see why both rook capturing pawns have to be promotable on dark squares.
johntromp wrote:
n9531l1 wrote:
What happened to the white pawns? The first two that captured the black rooks ended on dark-square-promotion files.
I don't see why both rook capturing pawns have to be promotable on dark squares.
When I read your comment #5772, I thought you were giving the rook captures as a way to let black pawns promote on dark squares. But I see now that's not the case. I'll have to think about this some more.
EvinSung wrote:
#5797
This is a legal position.
#5799
I think it is illegal. The knights and/or rooks cannot gain or lose a tempo.
#5797
I changed my mind. I think it's illegal. I saw the g8 knight could take the other one's place in an odd number of moves. But it doesn't help, since the b8 knight gets to d3 in an odd number of moves instead of even. I even made a proof game on my chess board, but forgot to make one of White's moves.
December_TwentyNine wrote:
Yeah sure. No one believes December until they actually see that it's more than likely illegal, if not definitely.
What do you think about #5791? Would it be legal without the pawn on h3?
EvinSung wrote:
#5805
Black's last move was the knight check. When that move is retracted, White has no previous move so the position is illegal. The a2 pawn had already moved to b3 to let a black pawn promote on b1, and the d2 pawn had already moved to c3 to release the c1 bishop (White has no promoted pieces).
One of the most common mistakes in beginners On The Board chess is changing the position of the queens.
Queen white must be on white square and black on black square.
Oct 8, 2021
0
#5738
Pan_troglodites wrote:
This is an illegal position.
It happens many times in real games.
Two bishops in the same color squares.
Considering pawns was not promoted
um that is so easy to find out
December_TwentyNine wrote:
n9531l1 wrote:
What do you think about #5791? Would it be legal without the pawn on h3?
It's hard for me to tell at this point.
One way to get an idea is to try making a proof game for the position. Another way is to think about what made the position illegal with the h3 pawn in place. But the best way is to look at the proof games EvinSung posted.
#5786 is essentially #5702 with colors reversed. Not surprising that the answer is the same as before. Next EvinSung should ask if changing the color of the a7 pawn would make the position legal.