# legal AND illegal positions

f or dxe5+ en passant.

EDIT: Wait no...

It cannot be fxe5, it must be dxe5.

Okay, so it's like this:

pompom wrote:

Okay, so it's like this:

CORRECT!!

Legal or illegal?
NinjaBear wrote:

I'm finding this humorous.

...!

Someone wrote earlier that the standard starting position is "legal with white to play, illegal with black to play."

Is there no way to traingulate the knights?

zezpwn44 wrote:

Someone wrote earlier that the standard starting position is "legal with white to play, illegal with black to play."

Is there no way to traingulate the knights?

Use post #56 for a hint about moving to different color squares.

I think this is illegal, but I'm still working through the thoughts.  Here is the diagram from post #24:

I agree with the fact that white needs to play e3, axb3 and bxc4 in order to give the bishop room to move to b1 from f1.  Since this is a light bishop, the only way for it to make it is to play Ba4 -> Bb3 (after axb3 and bxc4 are played) -> Ba2 -> Bb1.  White needs to execute this plan before black puts his bishop on a4.

The white pawn on c4 comes from the a2-square because axb3 and bxc4 is the only way for both a2 and b3 to be free for the light bishop to make its journey. This means the pawn on b3 comes from the b2-square.  The a-file is the only file that comes open for white's rooks to come out.  The white rooks need to come out before black plays Ra2.

One thing that was not mentioned was the fact that white needs to play Na1 before he plays b3.  Otherwise the knight will never get there.  Similiarly, black needs to play Nh8 before g6 is played.  And white's dark bishop cannot get out until white plays b3.  White's queenside rook can move out of the way, but the other rook needs to escape as well.  White's kingside rook cannot get out until white's knights, bishops,queen and king clears the way.  It would have to come out by playing Rb1 -> Rb2 -> Ra2 because the dark bishop cannot get out until white plays Na1 and b3 first.

b6 was never played (with a black pawn on a7) because black's dark bishop would never have a chance to reach b8.  However, b6 does get played once the dark bishop reaches a7 (or b8) so that black can free the light bishop.  This means that white's king can only reach black's backrank via g7.  In order for black to allow white to play Kh6 -> Kg7, black needs to play Nh8 and g6 first.  White's king needs to travel all the way across the backrank to b7 so that black can get one of his rooks back to g7.

Legal or illegal?

HongKongPlayer wrote:

Yes, but it has to be BLACK TO MOVE.

einstein_69101 wrote:

I think this is illegal, but I'm still working through the thoughts.  Here is the diagram:

I agree with the fact that white needs to play e3, axb3 and bxc4 in order to give the bishop room to move to b1 from f1.  Since this is a light bishop, the only way for it to make it is to play Ba4 -> Bb3 (after axb3 and bxc4 are played) -> Ba2 -> Bb1.  White needs to execute this plan before black puts his bishop on a4.

The white pawn on c4 comes from the a2-square because axb3 and bxc4 is the only way for both a2 and b3 to be free for the light bishop to make its journey. This means the pawn on b3 comes from the b2-square.  The a-file is the only file that comes open for white's rooks to come out.  The white rooks need to come out before black plays Ra2.

One thing that was not mentioned was the fact that white needs to play Na1 before he plays b3.  Otherwise the knight will never get there.  Similiarly, black needs to play Nh8 before g6 is played.  And white's dark bishop cannot get out until white plays b3.  White's queenside rook can move out of the way, but the other rook needs to escape as well.  White's kingside rook cannot get out until white's knights, bishops,queen and king clears the way.  It would have to come out by playing Rb1 -> Rb2 -> Ra2 because the dark bishop cannot get out until white plays Na1 and b3 first.

b6 was never played (with a black pawn on a7) because black's dark bishop would never have a chance to reach b8.  However, b6 does get played once the dark bishop reaches a7 (or b8) so that black can free the light bishop.  This means that white's king can only reach black's backrank via g7.  In order for black to allow white to play Kh6 -> Kg7, black needs to play Nh8 and g6 first.  White's king needs to travel all the way across the backrank to b7 so that black can get one of his rooks back to g7.

Those facts are true, but one player could always waste time by moving a piece back and forth.

pompom wrote:
HongKongPlayer wrote:

Yes, but it has to be BLACK TO MOVE.

the forks make it seem illegal.

HongKongPlayer wrote:

Legal or illegal?

wel... that was a lot longer..

My position was legal.

should be black to move