After the first 12 moves the following position was reached. I have just sacrificed a Rook on c8.
1...Ng5! Now it is a forced game.
2.Qe3 Ngxf3+ 3.gxf3 Nxf3+ 4.Ke2 [ 4.Kd1 Nd4+ and White loses the Queen.]
4...Qxc4+! [ 4...Nd4+ 5.Kd3! and there are no checkmating ideas.]
5.Kd1 [ 5.d3 Qc2+ 6.Bd2 Nxd2+-+ ]
5...Nd4+ 6.f3 Bxf3+ 7.Ke1 Nc2+ 8.Kf2 Qh4+ 9.Kxf3 Qh5+ 10.Kf2 Nxe3 11.Kxe3 Qe5+ 12.Kf2 Qf5+ 13.Kg1 Qxc8 Now it looks like we are starting from the initial position.
14.Bg2 e5 15.h3 Bc5+ 16.Kh2 0-0 17.Rf1 Rd8 18.Be4 g6 19.a3 f5 20.Bg2 e4 21.b4 Bd4 22.Ra2 Be5+ 23.Kh1 Qe6 24.Rc2 Qb3 25.Rc5 Qg3 1-0