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