Copycat Chess, Again

Your task is to reconstruct a chess game, which was played according to standard chess rules, given the following information:

• the first 7 moves by white were exactly copied by black (i.e. if white had played 1. e4 black would respond with 1. ... e5)
• whites 8th move left only one possible move for black, which was not a copied move
• this only possible 8th move by black checkmated white

This puzzle was created by Sam Loyd.

Hints

1. e4 e5

2. Ke2 Ke7

3. Ke3 Ke6

• My best attempt, so far: 1. e3 e6 $\;$ 2. g4 g5 $\;$ 3. Qf3 Qf6 $\;$ 4. Qg3 Qg6 $\;$ 5. Ke2 Ke7 $\;$ 6. Kf3 Kf6 $\;$ 7. Nc3 Nc6 $\;$ 8. d4 d5 $\;$ 9. Ne2 Ne7 $\;$ 10. Bg2 Bg7 $\;$ 11. Ne4+?? Qxe4# $\;$ or $\;$ 11. Ne4+?? dxe4#. – Mr Pie Oct 4 '18 at 22:15
• @user477343 The hints in the puzzle should make it a little easier. – Sleafar Oct 5 '18 at 5:23

Attempt 2:

https://lichess.org/editor/rn3b1r/p1ppnppp/bp2kq2/8/3pP3/BP2KQ2/P1PP1PPP/RN3B1R_w_-_-

One move for the king's pawn, two to get the king to e3, one to get the queen to f3, two to get the queen's side bishop to a3, and two to get the king's side knight to d4. The only response for Black is to take the checking knight with his pawn leading to mate.

It should be mentioned that:

The order that the supporting pieces are put into position is largely inconsequential. Therefore, we cannot determine the exact order of play. The only thing that we can be sure of is the final position of the game.

Update from El-Guest (you can delete this if you want, I just wanted to show a potential run of play based on the board provided to round out this answer and didn’t want to post another answer or comment because this looks good):

• Elder: just wanted to complete your answer without taking any of the credit for your hard work. Love your answer, +1 from me!! Hope to see you around here more often! :D – El-Guest Oct 5 '18 at 17:29
• Nicely done. A tip for the future, usually it's better to edit wrong answers instead of posting a new answer. – Sleafar Oct 5 '18 at 18:26

Final position as follows:

https://lichess.org/editor/r1bq3r/pppp1ppp/3bk3/3Np3/3nP1n1/3BK2N/PPPP1PPP/R1B4R_w_-_-

Reasoning:

1:

The fact that hint 3 moves the king to e3 and not d3 or f3 indicates that this is where he will be mated (the king wasn't blocking the way of other pieces given that he was the first to move and it would be a waste of a move to go to e3 when he could have moved directly to the other spots if he was needed there).

2:

The fact that black had only a single response on his final move indicates that he was in check and was forces to defend his king (too many other valid moves otherwise). This also indicates that the mating black piece did not mate by moving beside the white king (as this would require a protector of that piece, and therefore would give black a second method of capturing the checking white piece).

3:

Because of 2, the mating black piece must be positioned at a queen's or knight's movement away from both kings, and because 1 isolates the kings at e3/e6, the mating black piece must be at g4/g5 or h3/h6.

From here, it's fairly simple to construct the end position in 8 moves:

Given that the white king has three escape routes if he were in check at g3, we use moves 4 and 5 to bring in the queen side knight to block two of them, the white bishop to block the third off via move 6 and we use move 7 and 8 to get the checking/mating queen and knight in position.

• You are supposed to show all the moves leading to the mate, which you haven't done. And judging by your final position, your solution is not valid because the last black move isn't forced (black isn't forced to take the queen). – Sleafar Oct 5 '18 at 5:16
• In your third point, I'm not sure why it would be g4/g5 and not c4/c5. – Evargalo Oct 5 '18 at 9:57
• Actually already the 2nd point is not true. There is no reason, why the mating black piece can't stand next to the white king, as long as it's protected and can't be taken by another white piece. – Sleafar Oct 5 '18 at 11:44
• Ah of course. It's always the pawns that are the forgettable ones. I hadn't considered the possibility of the protecting piece being in a position where they could not take the checking white piece while also being in position to protect the mating black piece. – Elder Oct 5 '18 at 16:50

An attempt that fails short:

1.e3 e6 2.Qh5 Qh4 3.Ke2 Ke7 4.Kf3 Kf6 5.Ne2 Ne7 6.Ng3 Ng6 7.Be2 Be7 8.Qe5+ Nxe5# (alas not forced because of 8...Kxe5!)

After the hints, another attempt that is one move too long:

1.e4 e5 2.Ke2 Ke7 3.Ke3 Ke6 4.b3 b6 5.Ba3 Ba6 6.Be2 Be7 7.Bh5 Bh4 8.Nf3 Nf6 9.Bg4+ and the only move for Black is 9...Nxg4#

• This is really not an easy puzzle. I'll refrain from addtional comments to avoid giving misleading hints. – Sleafar Oct 3 '18 at 12:34
• Using one of the bishops is a good idea. – Sleafar Oct 5 '18 at 11:45