I've recently become interested in solving puzzles where you determine if a position is legal or not. For example, is this position legal?                                                                                                                                                      

Can someone produce a position that is legal AND illegal (depending on if the puzzle is white or black to move)? I should also add that neither side is in check.

Have fun...

JOH

Two black-colored bishops. No way for White to promote a Pawn as Black's Pwan wall isn't broken.

Thank you MRO314. It appears that it is just the definition of a stalemate!

Illegal. White would have had to move one of his queens to either c7 or b6 while the other was already at the other of those squares, meaning that Black would have had to move while in stalemate.

Yes, here is an example:

If it is white to move, this is legal.  If this was black to move, this is not legal.

legal or illegal?

it's obviously illegal because there are no kings on the board.

I'm finding this humorous.

Interesting.

Elegant solution in post #8 pompom.  It made me smile.

I disagree. White could bring his knight out, then black could, then white could bring a second knight out, then black could bring his knight back in. White brings a knight in, black puts a knight out, white puts a knight out, black brings his knight in, white brings a knight in black puts a knight out, white brings a... Yeah this isn't working out.

yeah, that is genious.

yeah, the knights can't lose a tempo (because it goes from a light square to a dark square and a dark square to a light square) and the rooks have only one square to go to.

Here are some more:

This is illegal no matter who's move it is impossible because there is no way the bishop could have gone to h8 as pawns can't move backwards and g7 is blocked!

That bishop could have been a promoted pawn.

Yes, I just said that the bishop was promoted.

very interesting topic