how to decide a position is legal or not ?
how can chess.com members decide it is legal or not ?
Is there a standerd methode ?
Welcome to the world of retro puzzles. Just use logic to decide it. For example, you can tell that these are all illegal easily:
Meanwhile, these ones are legal, although not as easily:
The good ones in this thread are just these made more complex.
No, there is no method to always determine them easily.
how to decide a position is legal or not ?
how can chess.com members decide it is legal or not ?
Is there a standerd methode ?
Welcome to the world of retro puzzles. Just use logic to decide it. For example, you can tell that these are all illegal easily:
Meanwhile, these ones are legal, although not as easily:
The good ones in this thread are just these made more complex.
No, there is no method to always determine them easily.
the last one is illegal as no one can give double check like this
Not so! There is a way.
the last one is illegal as no one can give double check like this
Yes, it is legal, just tricky. Here's the position before White's last move:
Don't forget about en passant.
Now the one above it, I just can't see. Black's rook could not have been anywhere else on his last move, and his king could not have been on g1 either. It looks illegal to me. Solution anyone?
the last one is illegal as no one can give double check like this
Yes, it is legal, just tricky. Here's the position before White's last move:
Don't forget about en passant.
Now the one above it, I just can't see. Black's rook could not have been anywhere else on his last move, and his king could not have been on g1 either. It looks illegal to me. Solution anyone?
Last move = ...exf1=R+
Don't forget about en passant.
Now the one above it, I just can't see. Black's rook could not have been anywhere else on his last move, and his king could not have been on g1 either. It looks illegal to me. Solution anyone?
Last move = ...exf1=R+
Nice. I didn't think about underpromotion...
every position is legal position if u consider chess 960
No. Just no. See the first two positions in post 1429. Neither is legal, 960 or otherwise.
every position is legal position if u consider chess 960
Not true, here's an illegal position, even in chess 960, because in chess960, the King must start between the two rooks, and clearly the two knights started on a1 and b1:
every position is legal position if u consider chess 960
Not true, here's an illegal position, even in chess 960, because in chess960, the King must start between the two rooks, and clearly the two knights started on a1 and b1:
Or else the rooks were captured on their home squares...
every position is legal position if u consider chess 960
Not true, here's an illegal position, even in chess 960, because in chess960, the King must start between the two rooks, and clearly the two knights started on a1 and b1:
What if one rook was at a1/b1, and was captured by a Black knight?
It has been a long time since I constructed chess problems, oh well. Not very interesting nor aesthetically pleasing, but eh.
EDIT: Oh, and my intended solution has a shortcut, even. Oh well; I did say it's not very interesting.
(11+13) Is the position legal?
It has been a long time since I constructed chess problems, oh well. Not very interesting nor aesthetically pleasing, but eh.
EDIT: Oh, and my intended solution has a shortcut, even. Oh well; I did say it's not very interesting.
(11+13) Is the position legal?
Yes. Black's king's rook was captured, so it doesn't matter that it has no path to emerge from behind the pawns. The other rook came from underpromotion of the a-pawn on f1, which is possible if all missing white pieces (both knights, a rook, a queen, and the f-pawn) were captured by it.
White's rook must have emerged from behind the pawns via the f-file after his f-pawn made a capture on e3 (which was subsequently captured by Black's pawn on its way to promotion).
The last move played was Black's Ne1-c2.
EDIT: Changing my answer to no, because White's light-square bishop has no path from behind the pawns, and it can't be the result of underpromotion due to the requirement that Black had to capture the missing pawn in order to reach f1.
Is this position lethal ?
It's legal, anyway.
Is this position lethal ?
It's legal, anyway.
And lethal.
Death by enforced gluttony!
Yes. Black's king's rook was captured, so it doesn't matter that it has no path to emerge from behind the pawns. The other rook came from underpromotion of the a-pawn on f1, which is possible if all missing white pieces (both knights, a rook, a queen, and the f-pawn) were captured by it.
White's rook must have emerged from behind the pawns via the f-file after his f-pawn made a capture on e3 (which was subsequently captured by Black's pawn on its way to promotion).
The last move played was Black's Ne1-c2.
EDIT: Changing my answer to no, because White's light-square bishop has no path from behind the pawns, and it can't be the result of underpromotion due to the requirement that Black had to capture the missing pawn in order to reach f1.
It is legal, though. Hint: are you sure black promoted on f1, and not on some other square?
Definitely 2 and 3
2.
3.
DavidMertz1 you're wonderful for taking out the time to put that 2gether....
....
....and wilford-n you are awesome for the checkmating solution !
TY you two....xoxo....Lola
Yes. Black's king's rook was captured, so it doesn't matter that it has no path to emerge from behind the pawns. The other rook came from underpromotion of the a-pawn on f1, which is possible if all missing white pieces (both knights, a rook, a queen, and the f-pawn) were captured by it.
White's rook must have emerged from behind the pawns via the f-file after his f-pawn made a capture on e3 (which was subsequently captured by Black's pawn on its way to promotion).
The last move played was Black's Ne1-c2.
EDIT: Changing my answer to no, because White's light-square bishop has no path from behind the pawns, and it can't be the result of underpromotion due to the requirement that Black had to capture the missing pawn in order to reach f1.
It is legal, though. Hint: are you sure black promoted on f1, and not on some other square?
Yes, I'm pretty sure. He couldn't have underpromoted on a1, the only other promotion square the pawn could reach, because the new Black rook has no way to get over to f1 from there. White's c1 bishop hasn't moved, so he couldn't get out from behind the pawns via the c-file without eating it first, nor could he have traversed the rank. So I'm sticking with no, but if you see another way, enlighten me. Inquiring minds want to know.
Title says it all. Post a position, and the Chess.com members will decide whether it is legal or not.
#1 is not legal, because there is no way that the king could get to this square, regardless its black or white, unless the pawn on g or b has moved at least once
#2
#3
#4
NOTE: Person needed to create puzzles.