New game: Meigo

[Luis Bolaños Mures]

Meigo is a drawless territory game for two players: Black and White. It is played on the intersections (points) of an initially empty square grid (board). There is also an off-board location called prison. Each player has access to a sufficient supply of stones of their own color. One of the two sides of each stone is marked.

DEFINITIONS

A chain is a stone along with all stones one can reach from it through a series of steps onto orthogonally adjacent stones of the same color. A liberty of a chain is an empty point orthogonally adjacent to it.

A stone is marked if its marked side is up, and unmarked otherwise.

PLAY

Black plays first, then turns alternate. On your turn, perform exactly one of these actions:

🌟 Remove an enemy stone from the prison.
🌟 Select an empty point. If there is a free path following the lines of the board between that point and an unmarked stone of your color, or it is your first turn of the game, place an unmarked stone of your color on the selected point. Otherwise, place a marked stone of your color on that point. Next, move to the prison all enemy chains without liberties. After this action, the stone you just placed must be part of a chain with at least one liberty.

You cannot place a marked stone and remove a marked stone on the same turn if your opponent just placed a marked stone.

The last player to perform an action wins.

To make the game fair, before the game starts, the first player places a number of black stones in the prison, and then the second player chooses sides. For handicap games, the weaker player takes Black and opens instead by placing on the board a number of unmarked black stones proportional to the skill gap between the players.

NOTES

To my knowledge, this is the naturally finite game that plays most like Go.

https://boardgamegeek.com/thread/3087559/new-game-meigo-minimally-overengineered-naturally

[Luis Bolaños Mures]

Revised rules to make the game even more like Go:

* * *

Meigo is a drawless territory game for two players: Black and White. It is played on the intersections (points) of an initially empty square grid (board). There is also an off-board location called prison. Each player has access to a sufficient supply of stones of their own color. One of the two sides of each stone is marked.

DEFINITIONS

A chain is a stone along with all stones one can reach from it through a series of steps onto orthogonally adjacent stones of the same color. A liberty of a chain is an empty point orthogonally adjacent to it.

A stone is marked if its marked side is up, and unmarked otherwise.

PLAY

Black plays first, then turns alternate. On your turn, play or hold. To hold, remove an enemy stone from the prison. To play, follow these steps:

1️⃣ Select an empty point.
2️⃣ If that point has a free path along the lines of the board to a marked friendly stone or to no friendly stones at all, and it is not your first turn of the game, place a marked friendly stone on the selected point. Otherwise, place an unmarked friendly stone on that point.
3️⃣ If the stone you just placed is part of a group with unmarked stones, flip all marked stones in the group to unmark them.
4️⃣ Move to the prison all enemy chains without liberties. After this, the stone you just placed must be part of a chain with at least one liberty.

You cannot place a marked stone and move a marked stone to the prison on the same turn if your opponent just placed a marked stone.

The last player to play or hold wins.

To make the game fair, before the game starts, the first player places a number of black stones in the prison, and then the second player chooses sides. For handicap games, the weaker player takes Black and opens instead by placing on the board a number of unmarked black stones proportional to the skill gap between the players.

NOTES

To my knowledge, this is the naturally finite game that plays most like Go.

https://boardgamegeek.com/thread/3087559/new-game-meigo-minimally-overengineered-naturally

[Luis Bolaños Mures]

Another revision, this time a small one:

* * *

Meigo is a drawless territory game for two players: Black and White. It is played on the intersections (points) of an initially empty square grid (board). There is also an off-board location called prison. Each player has access to a sufficient supply of stones of their own color. One of the two sides of each stone is marked.

DEFINITIONS

A chain is a stone along with all stones one can reach from it through a series of steps onto orthogonally adjacent stones of the same color. A liberty of a chain is an empty point orthogonally adjacent to it.

A stone is marked if its marked side is up, and unmarked otherwise.

PLAY

Black plays first, then turns alternate. On your turn, play or hold. To hold, remove an enemy stone from the prison. To play, follow these steps:

1️⃣ Select an empty point.
2️⃣ If that point has a free path along the lines of the board to a marked friendly stone or to no friendly stones at all, and it is not your first turn of the game, place a marked friendly stone on the selected point. Otherwise, place an unmarked friendly stone on that point.
3️⃣ If the stone you just placed is part of a group with unmarked stones, flip all marked stones in the group to unmark them.
4️⃣ Move to the prison all enemy chains without liberties. After this, the stone you just placed must be part of a chain with at least one liberty.

You cannot place a marked stone and move a marked stone to the prison on the same turn if the last stone added to the board is now marked.

The last player to play or hold wins.

To make the game fair, before the game starts, the first player places a number of black stones in the prison, and then the second player chooses sides. For handicap games, the weaker player takes Black and opens instead by placing on the board a number of unmarked black stones proportional to the skill gap between the players.

NOTES

To my knowledge, this is the naturally finite game that plays most like Go.

https://boardgamegeek.com/thread/3087559/new-game-meigo-minimally-overengineered-naturally

[Luis Bolaños Mures]

Another small revision:

* * *

Meigo is a drawless territory game for two players: Black and White. It is played on the intersections (points) of an initially empty square grid (board). There is also an off-board location called prison. Each player has access to a sufficient supply of stones of their own color. One of the two sides of each stone is marked.

DEFINITIONS

A chain is a stone along with all stones one can reach from it through a series of steps onto orthogonally adjacent stones of the same color. A liberty of a chain is an empty point orthogonally adjacent to it.

A stone is marked if its marked side is up, and unmarked otherwise.

PLAY

Black plays first, then turns alternate. On your turn, play or hold. To hold, remove an enemy stone from the prison. To play, follow these steps:

1️⃣ Select an empty point.
2️⃣ If the selected point is orthogonally adjacent to chains of both marked and unmarked friendly stones, flip all marked stones in those chains to unmark them.
3️⃣ If the selected point has a free path along the lines of the board to a marked friendly stone or to no friendly stones at all, and it is not your first turn of the game, place a marked friendly stone on the selected point. Otherwise, place an unmarked friendly stone on that point.
4️⃣ Move to the prison all enemy chains without liberties. After this, the stone you just placed must be part of a chain with at least one liberty.

You cannot place a marked stone and move a marked stone to the prison on the same turn if the last stone placed on the board was marked.

The last player to play or hold wins.

To make the game fair, before the game starts, the first player places a number of black stones in the prison, and then the second player chooses sides. For handicap games, the weaker player takes Black and opens instead by placing on the board a number of unmarked black stones proportional to the skill gap between the players.

NOTES

Meigo is the naturally finite game that plays most like Go. It was inspired by Cavity, a Go variant created by Michael Amundsen. Christopher Field provided valuable input that helped refine the rules of the game. The prison mechanism was introduced by Berlekamp and Wolfe in their book Mathematical Go.

[Luis Bolaños Mures]

Post by Luis Bolaños Mures
3️⃣ If the selected point has a free path along the lines of the board to a marked friendly stone or to no friendly stones at all, and it is not your first turn of the game, place a marked friendly stone on the selected point. Otherwise, place an unmarked friendly stone on that point.

Correction:

3️⃣ If the selected point has a free path along the lines of the board to a marked friendly stone or to no friendly stones at all, and you flipped no stones in the previous step, and it is not your first turn of the game, place a marked friendly stone on the selected point. Otherwise, place an unmarked friendly stone on that point.