1nb2br1/5qpp/r2ppk1n/pp3p2/P6P/2PPP3/1P2NPP1/R2QKB1R w KQ - 4 21
FEN state: 1nb2br1/5qpp/r2ppk1n/pp3p2/P6P/2PPP3/1P2NPP1/R2QKB1R w KQ - 4 21 ; Best move: a4b5
The current state of the chess board is: Black knight at b8, black bishop at c8, black bishop at f8 and black rook at g8. Black queen at f7, black pawn at g7 and black pawn at h7. Black rook at a6, black pawn at d6, black pawn at e6, black king at f6 and black knight at h6. Black pawn at a5, black pawn at b5 and black pawn at f5. White pawn at a4 and white pawn at h4. White pawn at c3, white pawn at d3 and white pawn at e3. White pawn at b2, white knight at e2, white pawn at f2 and white pawn at g2. White rook at a1, white queen at d1, white king at e1, white bishop at f1 and white rook at h1. White kingside and white queenside castles are available. Half move number is 4. Full move number is 21. White to move.