How about 31. ... a2+
Here's another of mine... I played a sort of Pirc or Modern Defense against a classical system by White:
Doug Burgess (1885) vs Blue Emu
1. e4 g6
2. d4 Bg7
3. Nf3 d6
4. Nc3 Nf6
5. Be2 O-O
6. O-O c6
7. h3 b5
8. a3 ...
This sort of defensive move is often a poor idea in flank openings... especially since I'm really more interested in controlling c4 (to support a possible Nb8-d7-b6-c4) than in pushing on to b4.
8. ... a6
Insurance against a central break by d5 (after Nbd7) which would otherwise leave my b-Pawn hanging.
9. Be3 Nbd7
10. Qd2 Nb6
Now White finally realizes that I'm interested in the c4 square... but his cure is worse than the disease:
11. b3 Bb7
12. Bh6 ...
Another poor idea. The removal of Black's fianchettoed Bishop won't make much difference in the center since Black is preparing to play e5, and White really isn't well placed to attack on the K-side. On the other hand, White might end up missing his own dark-squared Bishop.
12. ... Qc7
13. Bxg7 Kxg7
14. Bd3 e5
Now Black has what appears to be an extremely favorable version of a Ruy Lopez, Closed Variation! At this point, White seems to overlook something...
15. Ne2? c5
... with a couple of different threats.
16. c3 Bxe4
17. Ng5 Bxd3
18. Qxd3 h6
19. Ne4 Nxe4
20. Qxe4 f5
21. Qb1 c4
Now Black is simply a Pawn ahead, with a wonderful square at d5 for his Knight. This advantage is enough for Black to shift over to a K-side attack over the course of the next few moves.
22. b4 Nd5
23. Qc2 Qf7
24. de de
25. Rad1 Rad8
26. Qc1 f4
It is now going to be very difficult to stop moves like 27. ... f3, opening the position around White`s King. His next move is equivalent to resignation.
27. g4? fg en-passent
28. fg Qa7+
29. Kh2 Rf2+
30. Kh1 Ne3
31. Nd4 Qa8+
32. Resigns.
... not before time. Mate is forced.