May1708   crafty: 35. ♔c1 ♖c8+ 36. ♕c2 ♕xg1+ 37. ♔d2 ♕f2+ 38. ♔d1 ♖xc2 39. ♗xg7+ ♔xh7 40. b4 ♕d2# (eval Mat06; depth 10 ply; 5M nodes) 

Jan0809   KingG: 23.axb3, opening up the afile, was suicide. 

Sep2421   Brenin: Only the N on b3 prevents Qa1 mate, so attack it with 26 ... Nc5. If 27 Bxf6 then Qa2+ 28 Kc1 Nxb3+ (important that this is check, otherwise Black is mated on g7) 29 cxb3 Rfc8+ 30 Kd2 is all forced, and now 30 ... Qa5+, as in the game, is stronger than the more obviouslooking 30 ... Qxb2+ 31 Ke1 Qc3+ 32 Qd2, when Black's attack runs out of steam. 

Sep2421   butilikefur: White to play is nice. Anyhow...
The only chance is 26...♘c5 27. ♗xf6 (maybe 27. c3 but I think 27...♕a2 28. ♔c1 ♕xb3 with ♖a1 and ♕xb2 coming) 27...♕a2 28. ♔c1 ♘xb3 29. cxb3 ♖fc8 30. ♔d2 ♕xb2 and now there is 31. ♔e1 or 31. ♔e3. 31. ♔e1 ♕xg2 (if 31...♕c3 32. ♔f1 and no checks) 32. ♖xg2 gxf6 and h7 will fall but is it really winning? 31. ♔e3 ♖c3 32. ♔e4 (32. ♖d3 ♖xd3 33. ♔xd3 ♕xb3 34. ♔e4 [34. ♔e2 ♖a2+ loses] 34...♖a4 35. ♔f5 ♕d3 36. ♔g5 ♕e3 37. ♔f5 ♕f4 mate) 32...♖a4 33. ♔f5 (33. bxa4 ♕b4 34. ♔f5 ♕f4 mate) 33...♖f4 <have to be careful of 33...♕xg2 34. ♖xg2 ♖xf3 35. ♔g5 gxf6? [better is ♖xf6] 36. ♔h6 ♖a8 [to parry ♖g8 mate] 37. ♖g7 and how to stop ♖dg1 and ♖g8? > 34. ♔g5 ♕xg2 (34...♖c2 is interesting) 35. ♖xg2 ♖xf6 and the b, f, and h pawns are hanging So, did I miss something after 31. ♔e1... maybe after 29...♖fc8 30. ♔d2 there is 30...♕a5 31. ♔e3 (31. ♔e2 ♖c2) 31...♖c3! (31...♕c5 blocks the rook file) 32. bxc3 ♕xc3 33. ♖d3 ♕c5 34. ♔e4 (34. ♔e2 ♖a2) ♖a4 35. bxa4 ♕c4 36. ♔e3 ... not quite working. no idea. 

Sep2421
  al wazir: I got the first four moves, but was planning to play 30...Qxb2+. After 31. Ke1 Qc3+ 32. Kf1 , black is out of checks. In the game line, if 35. Kc2, then Rc8+ 36. Kb1 Qd3+ 37. Ka1/Ka2 Ra8#. 

Sep2421   mel gibson: I saw that but it was complicated as
Black was also under a serious attack.
Stockfish 14 follows the same line:
26... Nc5
(26. .. Nc5 (♘d7c5 ♗g5xf6 ♕a4a2+ ♔b1c1 ♘c5xb3+ c2xb3 ♖f8c8+ ♔c1d2
♕a2a5+ ♔d2e3 ♕a5b6+ ♔e3e2 ♖c8c2+ ♔e2f1 ♕b6b5+ ♔f1e1 ♖c2xg2 ♖g1xg2
g7xf6 ♖g2g8+ ♖a8xg8 h7xg8♕+ ♔h8xg8 ♖d1c1 f6f5 ♖c1c3 ♔g8h7 ♔e1f2 f5f4
♔f2e1 ♔h7h6 ♔e1f2 ♕b5b6+ ♔f2f1 ♕b6d4 ♔f1g2 ♕d4d1 ♔g2f2 ♕d1d2+
♔f2f1 ♕d2h2 ♖c3c6 ♕h2h3+ ♔f1f2 ♕h3g3+ ♔f2e2 ♕g3g2+ ♔e2d3 ♕g2xf3+
♔d3c4 ♕f3e4+ ♔c4b5) +7.51/32 181)
score for Black +7.51 depth 32. 

Sep2421
  agb2002: Black is two pawns down.
White threatens Bxf6.
Black can further weaken the white castle with 26... Nc5: A) 27.Bxf6 Qa2+ 28.Kc1 Nxb3+ 29.cxb3 Rfc8+ 30.Kd2 Qa5+ (prevents Ke1) A.1) 31.Ke2 Rc2+ wins decisive material.
A.2) 31.Kd3 Qb5+
A.2.a) 32.Kd2 Qb4+
A.2.a.i) 33.Kd3 Qd4+ 34.Ke2 Rc2+ 35.Ke1 (35.Kf1 Qxd1#) 35... Rxg2 36.Rxg2 (36.Rxd4 Rxg1+ 37.Kf2 exd4 38.Kxg2 gxf6  + [r vs 2P]) 36... Qb4+ and 37... gxf6 wins decisive material. A.2.a.ii) 33.Ke3 Qf4+ 34.Kd3 Qd4+ transposes to A.2.a.ii. A.2.b) 32.Ke3 Qb6+
A.2.b.i) 33.Ke2 Rc2+ 34.Rd2 Qb5+ 35.Ke3 (35.Kd1 Ra1#; 35.Ke1 Ra1+ 36.Rd1 Rxd1+ 37.Kxd1 Rxg2 wins decisive material) 35... Qxb3+ 36.Ke2 (36.Rd3 Qb6+ and 37... Rxg2 wins decisive material) 36... Rxd2+ 37.Kxd2 Qxb2+ with a winning attack. A.2.b.ii) 33.Ke4 Qb4+ 34.Ke3 (34.Kd3 Qd4+ transposes to A.2.a.i; 34.Kf5 Qf4#) 34... Qf4+ transposes to A.2.a.ii. A.2.c) 32.Ke4 Qb4+ transposes to A.2.b.ii.
A.3) 31.Ke3 Qb6+ transposes to A.2.b.
A.4) 31.b4 Qxb4+ doesn't help White.
B) 27.Nxc5 Qa1#.
C) 27.Kc1 Nxb3+ 28.cxb3 Rfc8+ as above.
D) 27.Rd3 (attempting to delay Black's attack) 27... Nxd3 28.cxd3 (28.c3 Qa2+ 29.Kc2 Qxb2+ 30.Kxd3 e4+ looks winning) 28... Qxb3 29.Bxf6 (due to 29... Rfc8) 29... Qxd3+ 30.Qc2 (30.Kc1 Ra1#) 30... Qxc2+ (better than 30... Ra1+) 31.Kxc2 gxf3  + [r vs P]. E) 27.h6 Rfc8 28.hxg7+ Bxg7 looks winning.
F) 27.Qg4 (to trade queens) 27... Qa2+ 28.Kc1 Nxb3+ 29.cxb3 Qxb3, followed by Rfc8, looks winning. 

Sep2421
  raymondhow: Came close on this one.. puzzle instinct told me 26...Nc5 was the only chance. I saw ahead that I would use a rook to check on the cfile, and that Qa5+ would be crucial. I didn't think it mattered which rook, so chose 29...Rac8+ thinking the rook on f8 might be useful for defense later. But no, the rook on a8 will be needed to threaten the back rank. (Lesson learned: thinking defense in a puzzle is a bad idea.) So I played the correct queen checks and then 32...Rc2+ with the wrong rook, which leads to a draw at best. 

Sep2421   Stanco: I solved it. Easy one.
I just analysed the position with the whit king on c1 and the solution came itself. 

Sep2421
  Teyss: I'm with <al wazir>, also went for 30...Qxb2+ which leads to equality at best after 31.Ke1 Qxg2 (there is nothing better) 32.Rxg2 gxf6 and 33...Kxh7. Looked at 30...Qa5+ but there were too many lines, need to learn to structure variations. The first moves are obvious because Black is under attack. Actually was hesitating to play 29...Rfc8+ or Rac8+ but the latter only brings equality at best because you want to keep the R on a8 to play Ra1+ in some variations as noted by <raymondhow>. Going through <agb2002>'s comprehensive analysis:  "A.2.b.i) (...) 37...Qxb2+ with a winning attack" is actually mate after 37.Ke3 Ra3+ 38.Ke4 Qd4+ 39.Kf5 Qf4#  "E) 27.h6 Rfc8 28.hxg7+ Bxg7 looks winning." Indeed, the pressure on g7 is temporarily gone and Black threatens 29...Qa2+ and 30...Nxb3#
click for larger view "F) (...) Rfc8, looks winning." Black still needs to be careful because of the threat on g7. SF gives 30...Kd2 (else Rc8+ and mate) Ra4 (better than Bxg5+) 31.Qg2 31...Rc8 32.Ke1 (else Rc2+) Rc2 and White loses the Q or gets mated.
click for larger viewDifficult indeed. Kudos to those who found the entire combination with all variations. 

Sep2421
  chrisowen: Waffles I instigate hiker Nc5 gungho liker abridge likes waffles i instigate liker cup holder muffles jaw digits liker disguise instigate under banes bavarian knight puzzle zoran query its champion i liker ofsted its prang its wu its why blitz liker cio creaks chegg its win joggies liker gas jugglers chunder again emanate liker basically led its mooted its I ooh gal its haggard jiffy kibitz it ze conk its i likes fluff daddy garcon gag goodness liker hatch its designate threw its wu or buzzy its lamb its Nc5 vibrant! 

Sep2421
  chrisowen: Macks aka its nifty its dulcit tone key it lass a tie bet hall its dream coat nc5 blubber no? 

Sep2421
  chrisowen: Ditto boggles the inclusive no Nc5? 

Sep2421
  Dionysius1: I got as far as 29...Rfc8, and felt pretty pleased with myself. My reckoning is that I stopped short of a forced conclusion on the assumption the position looks so good from there that I'll find something over the board when it happens.
Weird, but then that seems to be the basis for White's resignation  sort of "the position seems overwhelming, I assume he's got it all worked out" I'm not totally seriously claiming the full solution on that basis, but it's like a moral victory! 

Sep2421   Refused: <agbe2002: [...] C) 27.Kc1 Nxb3+ 28.cxb3 Rfc8+ as above. > Nope. Not quite the same. The difference is that white can recapture with the Bishop on d2 in that line.
29.Kd2 Qa5+ 30.Ke3 Qb6 31.Ke2 Rc2+ 32.Rd2 Rxd2 33.Bxd2 and now Qd4 is not a check. Black is still winning after 29...Qxb3 as white's king is poor boy, and just gets no sympathy. 

Sep2421   saturn2: G. 27.c3 can be mentioned. It loses the Nb3 but there are still the threats against the black king. 

Sep2421   Stanco: The line after 30...Qa5+, as it's played in the game, is actually forced because white queen (mates) on f4 otherwise 😁.
Queen's maneuvering which follows after 34...Qd4+ resembles the premate down along the long diagonal in Queen vs Rook endgame 🙂 35.Ke2 Qxb2+ 36.Kd3 Qd4+ 37.Ke2 Ra2+ 38.Ke1 Qa1# (if 35.Kc1 Rc8 36.Kb1 Qd3+ 37.Ka1 Ra8#
plus a note: When you move your queen you're equal to move half of your units eventually! You better be precise at it, it's not a small potato ☝️ 
