Find the shortest chess game with 18 queens?

From the *starting position of a chessboard, you need to move the pieces to end up with 18 Queens following the chess rules at all times (this includes white moves first). The solution is the series of moves (not the final position, as there are plenty).

Having other remaining pieces is possible and allowed (e.g. a remaining bishop + the 18 queens and 2 kings).

_{* starting position FEN: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1}

_{see also the orignial question on chess stackexchange}

Answer

This is known as the "18-Queens Problem". I found this well-known solution by Friedrich Burchard & Friedrich Hariuc (1976) in 96 Half-moves. I can't make a claim to its optimality, but by looking at it and seeing that no better can be found, I'd say it may well be optimal.

1.e4 f5 2.e5 Nf6 3.exf6 e5 4.g4 e4 5.Ne2 e3 6.Ng3 e2 7.h4 f4 8.h5 fxg3
9.h6 g5 10.Rh4 gxh4 11.g5 g2 12.g6 Bg7 13.hxg7 g1=Q 14.f4 h3 15.f5 h2
16.b4 a5 17.b5 a4 18.b6 a3 19.Bb2 Ra7 20.bxa7 axb2 21.a4 b5 22.a5 b4
23.a6 b3 24.c4 h1=Q 25.c5 h5 26.c6 Bb7 27.cxb7 c5 28.d4 c4 29.d5 Nc6
30.dxc6 c3 31.c7 c2 32.c8=Q c1=Q 33.b8=Q Qcc7 34.a8=Q d5 35.a7 d4
36.Nc3 dxc3 37.Qa6 c2 38.Qa8b7 c1=Q 39.a8=Q Qhd5 40.gxh8=Q+ Kd7 41.g7

bxa1=Q 42.g8=Q b2 43.f7 b1=Q 44.f8=Q h4 45.f6 h3 46.f7 h2 47.Qfa3 h1=Q
48.f8=Q exf1=Q+

I used the same PGN viewer as OP for consistency.