Brandubh 7x7

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Hagbard
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Re: Brandubh 7x7

Post by Hagbard » Mon Nov 29, 2021 10:04 pm

Alex Hnefatafl sent this post:

Introduction

Despite the lack of computer analysis, I can confidently say that brandubh has a much smaller tree of possible moves than any checkers on 64 boards. At the same time, the percentage of useful combinations is very small. As a result, this option can be considered only as training and is not an indicator of the player's skill. All combinations can be learned with due diligence.

There is only one option for starting the game and is symmetrical for all sides. This is d2-e2. Since d2-g2 as black leads to an instant loss without compensation, and on the move d2-f2 there is a winning combination as in the example game. (1) d2-f2; d3-f3 2) f4-f5; e4-e1 3) ×f2-f1; f3-a3 4) b4-b5;c4-c2 5)...) And then black cannot stop the escape.

The most popular response from White to the first move d2-e2 is c4-c2. Beginners often make the wrong move 2) b4-b2, which immediately leads to a defeat after the reply 2) ...; d3-a3. This is followed by: 3) × b2-a2; c2-c7 4) d6-e6; d5-b5. And it turns out the same position as in the case of an erroneous first move d2-f2.

The most popular continuation is 1) d2-e2; c4-c2 from the side of black is 2) d6-e6; ... Then, as a rule, follows: 2) ...; d3-a3 3) c6-c5. The resulting position is roughly equal. White cannot immediately start to run away to the corner because of 3) ...; d4-d3 4) × d7-d6; d3-b3 5) d1-a1; ... Therefore, it is necessary to look for another way out after the move 3) c6 -c5 Move a piece to d5 or e4.

It is also worth considering the second continuation on moves 1) d2-e2; c4-c2. Namely move 2) b4-b3. The rest of the answers are more passive and have a dubious chance of winning. For a more detailed analysis this format is not enough, therefore, I will limit myself to analyzing a typical black error. 1) d2-e2; c4-c2 2) b4-b3; c2-b2. The move 3) × d1-b1 is a mistake, since what follows is 3) ...; d3-g3 4) f4-f5; d4-d1. After this move White is guaranteed to win.

Also, we have not considered White's second answer. Namely 1) d2-e2; d3-d2. It might be worth discussing. In any case, building AI according to the rules of the brandubh would be a big step forward. I advise you to pay more attention to the rule of repetition of moves (White always loses on repetition). It acts not only with respect to 2-4 cells, between which there is movement, but also with respect to the entire orthogonal.

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Hagbard
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Re: Brandubh 7x7

Post by Hagbard » Sun Jan 16, 2022 9:46 pm

Damian Walker describes a version of Brandubh rules in a leaflet:
http://www.cyningstan.com/data-download ... ub-leaflet
Throne friendly to all. Corners hostile to all.
King captured by 2 everywhere, even on and next to the throne.
It is a simple small-board-effect that details of the normal rules may break down on the smallest board 7x7.
The 7x7 king has but 4 men, all placed right next to the throne, and as soon as the king leaves the throne, they could all immediately be captured, were the throne hostile.
So to avoid that the throne must be friendly.

Were the corners friendly too, however, then attackers could easily block the way to the corners by standing next to them.
So the corners must still be hostile.

A normal throne protects the king well. Too well on the small board 7x7.
So in the rules described by Walker, the king is less protected and can be captured by two attackers everywhere also in the center of the board.

These changes seem a natural consequence of the small board 7x7.
But the game balance is always a surprice and one can never know before a thorough test.

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