Lesson
Black to move. Main line: 17... Be6 18. Bxb6 Bxc4+ 19. Kg1 Ne2+ 20. Kf1 Nxd4+ 21. Kg1 Ne2+ 22. Kf1 Nc3+ 23. Kg1 axb6 24. Qb4 Ra4 25. Qxb6 Nxd1
17...Be6!! develops the bishop and permits 18.Bxb6. The point is 18...Bxc4+: Black begins a series of checks before White can consolidate the queen gain.
The knights repeatedly force the king between f1 and g1 while collecting material. By 25...Nxd1, Black has recovered more than enough and still controls the initiative.
The move is brilliant because the offered queen is not the end of the calculation. It is the first move in a long forcing sequence where coordination outweighs nominal material.