Sometimes, you get the opportunity to play a move that accomplishes several things at the same time, kinda like a linchpin move that holds everything together. I infiltrated my opponent's position quite well, but no winning combination has yet been found to force a win. Black played 20...Qa5-Qa6 (diagram) attacking the rook on b7. This is the sort of move that may look reasonable at first glance, but it actually loses big time. White's 21. Nc5! defends the rook, and attacks the black queen at the same time. But this move brings the house down since it opens up a line of attack on the f7 square. That's the real problem. Black played 21... Qc6 completely missing the point. There truly wasn't any game-saving move to play. After 22. Qf7+, the game was over.