An Antichess Puzzle

Question

There's a fairly popular alternate version of chess called Antichess, or Losing Chess, or about seventeen other names. In this variation, the pieces move as usual, but the rules are slightly altered.

Antichess Rules

1. A player wins when they are stalemated or have no pieces remaining on the board.
2. The King acts like a normal piece and can be captured.
3. If a player can capture a piece on their move, they must. They can choose between two different pieces that they can capture (so a rook on a1 can choose to either capture a piece on a2 or a piece on b1.

All of this being said...

Black to move and win on white's 16th move (with best play).

Note: the no-computers tag is to prevent people from just plugging it into a computer that has an Antichess option.

Good luck!

Answer 1

Since nobody has proposed an answer yet, I will offer some thoughts:

It is possible to start solving this by elimination. If we allow White to make a non-capture, we won't get all our pieces taken in time. Sure, some could remain and get stalemated, but I consider it unlikely but for one or two pawns. And at the beginning at least, giving too much choice to White would make this puzzle unsolvable.

For the sake of clarity, I'll add one symbol to the usual chess notation: '£' means 'forced move'.

As a consequence, 1...d5? cannot be the answer: 2.ed5£ Qxd5£ and White won't capture on his third move. The same goes for 1...h5? 2.Qxh5£ Rxh5£, for 1...Na6? and 1...a6?.

1...f5 is possible, but it seems interesting to drag the Bf1 out: 1.e4 b5!? 2.Bxb5£ d5 when White has too lines:

3.ed5 Qxd5£ 4.Bxe8£ Qxa2/d2 will give White choices for several moves between capturing the bQ or capturing Pf7-Ng8 with the bishop.

3.Bxe8 Qxe8£ 4.ed5 Bg4 5.Qxg4£ drags the wQ out - but soon black will have to take himself.

A difficult puzzle.

Answer 2

First of all, antichess has been weakly solved in 2016 : White can force a win with 1.e3 Moreover there are 3 main 'losing lines' for white : d3, d4 and e4.

The majority of the experienced antichess players can force a win against these 3 moves with black. I learned the e4 counter ~1 year ago in order to counter inexperienced Lichess players : I obviously couldn't remember it perfectly after a year but it took me ~20 minutes to fully remember the strategy.

You can try putting it on a chessboard and understanding it ; it's not that complicated :

1. e4 b5 2. Bxb5 Nf6 3. Bxd7 Nxe4 4. Bxe8 Qxd2 5. Qxd2 Nxd2 6. Bxf7 Nxb1 7. Rxb1 Rg8 8. Bxg8 g6 9. Bxh7 e5 10. Bxg6 e4 11. Bxe4 a5 12. Bxa8 Ba3 13. bxa3 a4 14. Rxb8 Bh3 15. Nxh3 c6 16. Bxc6#

The hardest here is the a5-a4 maneuver, allowing black to be stalemated, therefore winning on white's 16th move.

The counter-intuitive move that MUST be learned if you want to solve this puzzle is

Black's second move : 2..Nf6! (d5 probably works too, but I never learned it. The main reason is that it gives white 2 lines, therefore it's harder to learn.)