To add to the misery, I had a winning position in my game on move 14, but didn't find either of the two sequences which would have won. Here's the position.
I played 14. ... dxe4 after a long think, having rejected 14. ... Nxe4 on account of 15. Qxd5, eg 15. ... Nxc3 16. Qxf5 Nxb1 17. Qxc2 Bb4 18. Be3, when the b1 knight is doomed and white wins. Instead, after the mass-liquidation with 15. Qxc2 exf3 16. Qxf5 fxg2+, we agreed a draw. See if you can spot the winning sequences I should have played, without a computer or moving the pieces around.