4kb1r/pr3p1p/bP4pn/3pP1B1/2pP4/6PP/1PP1PQB1/1R1n1KNR w k - 4 21
FEN state: 4kb1r/pr3p1p/bP4pn/3pP1B1/2pP4/6PP/1PP1PQB1/1R1n1KNR w k - 4 21 ; Best move: b1d1
The current state of the chess board is: Black king at e8, black bishop at f8 and black rook at h8. Black pawn at a7, black rook at b7, black pawn at f7 and black pawn at h7. Black bishop at a6, white pawn at b6, black pawn at g6 and black knight at h6. Black pawn at d5, white pawn at e5 and white bishop at g5. Black pawn at c4 and white pawn at d4. White pawn at g3 and white pawn at h3. White pawn at b2, white pawn at c2, white pawn at e2, white queen at f2 and white bishop at g2. White rook at b1, black knight at d1, white king at f1, white knight at g1 and white rook at h1. Black kingside is the only castle move available. Half move number is 4. Full move number is 21. White to move.