Top players usually follow positional and strategic principles, but they also know when to deviate, as in the following game.

Yu Yangyi of China, currently ranked No. 18 in the world, lost in the finals of the Tradewise Gibralter Masters in January to Hikaru Nakamura, but he at least he made it that far. Along the way, he beat Valentin Dragnev, an Austrian international master, by playing an unorthodox, but extremely effective opening. 

Dragnev, Valentin vs. Yu Yangyi
Gibraltar Masters 2017 | Caleta ENG | Round 7.4 | 30 Jan 2017 | ECO: B46 | 0-1
1. e4 c5 2. Nf3 e6 3. d4 cxd4 4. Nxd4 Nc6 5. Nc3 a6 6. Bf4 This move has become popular lately, but I don't like it. Black gains a strong center quite quickly and White is not really in any position to fight for control of the d6 square.
6... d6 7. Nxc6 bxc6 8. Qd2 Be7! The best move order.
8... e5 9. Bg5 This is the best square for White's bishop. Now it gets there in one move instead of two.
9... Nf6 10. O-O-O Be7 11. Bxf6 gxf6 12. Bc4 White is clearly better.  )
9. h4!? I have never seen this move before in this position, but it makes some sense -- White wants to put the bishop on g5. But I think it is too slow.
9. O-O-O e5! 10. Be3 Nf6 And White's bishop is on e3. That is a worse square for it than g5. After
11. Bg5 Be6! It is clear how much the tempo matters. White is unable to get his bishop to c4 and Black is absolutely fine.  )
9... e5! 10. Bg5 f6! 11. Be3 f5! Forcing, ambitious, and strong. Black wants to control the whole center.
12. Bg5 fxe4 13. Nxe4 d5 14. O-O-O Nf6! 15. Nxf6+?!
15. Qc3! This was much more resilient. After
15... Bd7 16. Nxf6+ gxf6 17. Bh6 At least Black cannot play Bh6, and White can soon play f4.  )
15... gxf6 Black's center is massive and strong.
16. Bh6 Qb6
16... Be6 This looks more natural to me but it would probably transpose to what was played in the game.  )
17. Be2 Be6! Black makes a hiding spot for his king on d7.
18. Bh5+? This misplaces White's bishop and forces the Black king to the square that is best for it.
18. f4 White needed to create counterplay. The position would remain somewhat unclear.  )
18... Kd7 White is probably dead lost. The Black king on d7 is safe behind the mass of center pawns, any endgame will be extremely difficult for White, and the White king will soon be under fire.
19. f4 Too little too late.
19. Be3 The engine recommends this move, but after:
19... Qb4 20. Qxb4 Bxb4 Black is clearly in the driver's seat.  )
19... Rhb8! There's nothing happening on the kingside, and the rook will be very useful on a8.
20. b3
20. Qc3 Bb4 21. Qb3 Qc5 White will not be able to hold this position together.  )
20... a5! Simple and devastating. Black threatens a4, after which all of Black's pieces will be aimed at the White king, and there is nothing White can do about it.
21. fxe5
21. a4 Qc5! Threatening Rxb3.
22. Kb1 Bf5 And White would be helpless.  )
21... a4! Not wasting any time, Black goes for mate.
21... fxe5 22. Bg7! And White could try to move his bishop back to b2 for defense.  )
22. Qf4
22. exf6 axb3  )
22... axb3 23. axb3 Qa5! This cuts off the d2 square, so the White king cannot escape to the center.
24. Bg4 Qc3! 25. Bxe6+ Kxe6 26. Qg4+ f5! An easy move to find, but still important. White is out of checks and completely helpless.

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Samuel Shankland is a United States grandmaster ranked No. 4 in the country. He is a professional player and recipient of the Samford Fellowship in 2013, the most prestigious award in the United States for young chess players. He was also a member of the team that won the gold medal at the 2016 Chess Olympiad. He is at @GMShanky on Twitter, has his own site, and is also on Facebook.