Can you think about an impossible position ?

@NobodyReally I'll give you a hint if you're stuck :)

@soni777 There are billions of ways to reach this position. With either player to move and with the white king on either d8 or e1.
Probably you are referring to castling rights but then you would have to rephrase the problem/question.

@NobodyReally the problem shouldn't need to be rephrased, as the FEN says that white has castling rights on both flanks.

@soni777 Ok, but when I open the position I don't see castling rights mentioned anywhere!

@NobodyReally that's what makes this puzzle difficult :)
2r3r1/8/8/8/8/4k3/4b3/R3K2R b KQ - 0 1 is the FEN, which is displayed at the bottom of the screen below the analysis board. KQ means white can castle kingside or queenside while black cannot castle.

Anyway, if white indeed has castling rights on both sides, then the position is impossible with black to move and is an easy draw (Rh3+) with white to move.

#35, Ok, I didn't know that. I never use FENs.

any position with 3 connected pawns on someone's 2nd rank and 1 pawn on the 3rd rank above the middle pawn is unachievable (all pawns are his)

pawn on the first or 8th row
3 kings

This position is impossible as the knights cannot triangulate to get to the starting position, but with black to move.

lichess.org/editor/rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR_b_KQkq_-