[White "White"] [Black "Black #1"] [FEN "2br1rk1/1pp1bppp/p1p2n2/4p1B1/1q2P3/2NP1NP1/PPP2PBP/R1Q1R2K w - - 0 0"] {Why is this position illegal ? - Black has doubled c-pawns, but white is not missing any pieces, so there could not have been a capture on c6 _MARK:c6-7_} *

[White "White"] [Black "Black #2"] [FEN "r3r1k1/pppR1p1p/n1n2qpQ/1B5b/4P3/P1P1BP2/1PP1N1PP/R4RK1 w - - 0 0"] {Why is this position illegal ? - White has 3 rooks. The 3rd rook is not a promoted piece because White has all 8 pawns _MARK:a1,d7,f1_} *

[White "White"] [Black "Black #3"] [FEN "2kr3r/pp4b1/1qpN3p/5Qp1/8/P3P1P1/1PP3P1/2KR2Nn w - - 0 0"] {Why is this position illegal ? - Black is in an impossible double check _MARK:d6,f5_} *