# Fabi and Mag played chess again

Fabi and Mag love chess, and I love to watch them playing together. I am not such a strong player myself, but I am an excellent spectator! The three of us were having a nice evening around a chess table and a bottle of wine, and after Mag won the first round, they switched colors and started a revenge at once. This time Fabi was White.

After each player had made four moves, I couldn't help it and exclaimed:
"You did it again!
- What have we done ?, asked Mag.
- Look, I explained, it is just as in the previous game: you have each played four moves, and some pieces have been taken, but all the remaining units are on their possible starting squares. Once again!
- Well, replied Fabi with a grin, at least this time I'll probably win: look, I already have a three points advantage."
And he moved his hand toward his rook to play his next move.

What was the position, and how did the game start ?

TL;DR

Find a chess position:

• that is reached after four moves by each player,
• where White has a three points material advantage,
• where all the remaining units stands on the same squares as at the beginning of a game.
• where a white rook can move.

Remarks

• A pawn is worth 1 point, a bishop a or knight 3 points, a rook 5 and a queen 9. White's 3-points advantage could be, e.g., 3 extra pawns, or one extra knight, or a rook and a pawn vs one bishop, or a queen vs a rook and a pawn.

• The parts in italics (about the white rook) have been edited in in order to limit the number of possible answers (hopefully to one). Without this additional constraint, Nate Schulz found an excellent (but unexpected for me) solution. Please upvote his answer because I feel a bit guilty not to give him the check!

• This puzzle is an entry in Fortnightly Topic Challenge #40: Retrograde Analysis.

This should work:

1. Nf3 Na6 2. Nd4 (or Ne5) c6 3. Nxc6 Rb8 4. Nxb8 Nxb8

White captured a rook and a pawn (6 points), black a knight (3 points) and White's next move can be Rg1.

The mirrored version doesn't work:

1. Nc3 Nh6 2. Ne4 f6 3. Nxf6 Rg8 4. Nxg8 Nxg8

because

White's third move would then be check.

• Congratulations. This is the expected solution. Black can also play (descriptive notation) ...KP4 instead of ...QBP3. – Evargalo Oct 19 '18 at 13:45
• Ah, that works too (also, in my solution Black's 1st and 2nd move can be switched). Thanks! – Glorfindel Oct 19 '18 at 13:49

1. e4 Na6
2. Bxa6 d5
3. exd5 Qxd5
4. Bf1 Qd8

• Congratulations, that works. But it is bad news for me, since it is not the answer I was intending... – Evargalo Oct 18 '18 at 16:28
• A variation on this theme would be (base 64; rot13 does a bad job at encrypting chess moves; decoder here) MS4gZTQgZDUgMi4gZXhkNSBCZzQgMy4gUXhnNCBReGQ1IDQuIFFkMSBRZDg= – Glorfindel Oct 19 '18 at 13:08
• Nice. Yet another solution... – Evargalo Oct 19 '18 at 21:08

The closest I can manage to get is:

1. a3 b5
2. a4 Bb7
3. axb5 Ba6
4. bxa6 Nbxa6

or

1. a4 b5
2. axb5 Ba6
3. bxa6 Nbxa6

The Problems:

Either the knight is left out on the a6 square or white is forced to move a piece from the beginning position on turn 4.

Hope this helps someone else