rn1qb1nr/2p1p3/3k4/p1Np1ppp/1P1NPP2/RP4PP/2PP4/b1B1KB1R b K - 3 21
FEN state: rn1qb1nr/2p1p3/3k4/p1Np1ppp/1P1NPP2/RP4PP/2PP4/b1B1KB1R b K - 3 21 ; Best move: a1d4
The current state of the chess board is: Black rook at a8, black knight at b8, black queen at d8, black bishop at e8, black knight at g8 and black rook at h8. Black pawn at c7 and black pawn at e7. Black king at d6. Black pawn at a5, white knight at c5, black pawn at d5, black pawn at f5, black pawn at g5 and black pawn at h5. White pawn at b4, white knight at d4, white pawn at e4 and white pawn at f4. White rook at a3, white pawn at b3, white pawn at g3 and white pawn at h3. White pawn at c2 and white pawn at d2. Black bishop at a1, white bishop at c1, white king at e1, white bishop at f1 and white rook at h1. White kingside is the only castle move available. Half move number is 3. Full move number is 21. Black to move.