The Poisoned Bun: Winning by Giving Something Away
In 26,000 AI-vs-AI games, there is a move where Black deliberately helps an enemy stone on move 5, letting a white stone that couldn't move start moving again. Black's win rate after playing it was 98%. Give your opponent something, and take something bigger. This is bocch's "Poisoned Bun".
What you can give away in bocch
Chess has the gambit, where you sacrifice a piece to gain an advantage. But bocch has no captures at all. What you can give away in bocch isn't stones, but numbers and first arrival.
We counted every move in the AI's 26,000 games where a player gave something away on purpose.
- The "wake-up", landing next to an enemy loner and letting it move, gave the giving side a 57–67% win rate. It was actually a move that tends to win.
- Conceding the first goal, letting the opponent make the first arrival, was a loss in the opening at 44%. But in the middlegame it was 65%, and in the endgame 98%.
Giving something away isn't a bad move in itself. What matters is what you get in exchange.
The wake-up: wake the enemy, strengthen your own
This position arises after Black 6f→5e, White 5a→5c, Black 1f→2e, White 1a→2b.
Look at White's 5c. It has no neighbors, so its number is 0. It is all alone and can't move. Here Black plays 2f→4d and wakes up White's 5c.
With a neighbor now beside it, White's 5c goes from 0 to 1. The white stone that couldn't move can move now. Black has woken up the enemy.
What Black got in return was 5e's number. With 4d now next to it, 5e went from 2 to 3, and its jumping distance grew by one square. The AI's evaluation was +83 for 2f→2d, which gives nothing away, versus +133 for 2f→4d. In the 40 games that reached this position, Black won 98%.
Here is how the actual game continued. White 2a→2c, Black 3f→5d added another neighbor to 5e, making it 4. White moved its newly awakened 5c back to 5a, and Black played 5e→1a, a huge four-square jump for the first stone across.
The draw-back: pull back to build power behind
Here is another line: Black 6f→5e, White 5a→3c, Black 1f→2e, White 1a→2b, Black 2f→4d, White 2a→2c, Black 4f→4c, White 3a→5c. Black to move.
Black chose to pull 4c back three squares to 4f, like drawing back a bowstring.
The pulled-back 4f is next to 3f and 5f. Both of their numbers go from 1 to 2, and stones that were sleeping at the back can now jump. In exchange, a path opens from White's 3c to 6f. White can make the first arrival. This is the Poisoned Bun.
In the actual game, White 5c→5b, Black 5f→5d, and then White ate the bun: 3c→6f, the first goal.
But the white stone that arrived on 6f is next to Black's 5e. 5e's number goes from 3 to 4. That was the poison. Black jumps four squares with 5e→5a and immediately catches up.
White's best is not to eat the bun. Even so, Black's advantage holds. In the same position, Black won 17% when it played 5f→4f without pulling back, and 76% when it pulled back.
Summary
- What you give away isn't stones, but numbers and first arrival.
- Waking up an enemy stone pays off if your own numbers grow.
- The draw-back builds power in the stones behind.
- You can concede the first arrival if you can stop the second.
This article is a written version of episode 23 of the YouTube series "bocch定跡研究". The positions are taken from actual AI-vs-AI games.