[FEN "r4rk1/pb1q1pp1/1p2p2p/4B3/2BPn3/P3P3/5PPP/2RQ1RK1 b -"]

18... f6 19. Qg4


w b wb bw | w b wb bw

b     an
    


18...f6      an
    


19. Qg4      an