4k3/4p3/8/b7/1BR1p2p/1Q3P2/5N2/4K3 w - - 0 1
r1bq1rk1/pppp1ppp/2n2n2/4p3/2B1P3/3PPN2/PPP3PP/RN1QK2R b KQ - 1 7
6k1/6pp/R2p4/p1p5/8/1P1r3P/6P1/6K1 b - - 3 37

# both can castle queen only
r3k2r/8/3B4/8/8/3b4/8/R3K2R w KQkq - 0 1
r3k2r/8/3BB3/8/8/3bb3/8/R3K2R w KQkq - 0 1
r2bkb1r/8/8/8/8/3bb3/8/R2BKB1R w KQkq - 0 1

# illegal positions
4k3/8/8/8/7b/8/8/4K3 b - - 0 1
2r1k3/3P4/8/8/8/8/8/4K3 w - - 0 1