In this variation white plays to obstruct the bishop with a timely pawn sacrifice.
21... P7e 22 R4f P5e (22... P6f 23 Bx6f G6e 24 P4d! S4b 25 Px4c+ Sx4c 26 B4d!! Sx4d 27 Sx4d with threats of S4c= or N4e) 23 P4d (if 23 Px5e S3a and the silver will participate in the game) S5d (As usual, white tries to avoid exchanges. If 23... Px4d 24 Sx4d Sx4d 25 Rx4d P*4c 26 Rx6d!! Kx6d 27 Bx5e K6c 28 S*5d!! (since 28... Sx5d is met by 29 G*6d mate) K6b 29 N4e with a winning attack) 24 Px4c+ Sx4c (24... Gx4c 25 Px5e P*4e 26 R5f wins two generals for the bishop and breaks in) 25 Bx5e! (note how readily black sacrifices bishop for gold with the safety of the crab castle, in this case to denude white's king) Gx5e 26 Px5e B*2h 27 P*3h (although knight and lance are close in value, this drop keeps the white bishop out of play) Bx1i+ 28 P*4d S5b 29 G*5d K7b 30 P4c+ winning easily.