Yesterday, I was daydreaming about Go and had an idea that never occurred to me before: what if Go had inner walls? How would this re-shape the game?

At first, I considered the variant to be “Tengen no Go”: have a wall/pillar/coin at the center of the board to prevent any player from playing there. I thought this would be interesting because every game of Go starts from the corners and meet at the center. How would the symmetry of removing the center impact the game?

Turns out, some fellow Go players on Reddit commented that the game would devolve into “Mirror Go”, a game where White always has the advantage over Black. Thus, a generalization of the idea took place: what if any intersection could be removed as a valid playing spot? This has the potential of creating even more interesting asymmetries.

After discussing with players online, here are the rules I propose for the Coin Go variant:

In Coin Go, a stone cannot be played on certain intersections of the board by either player. A coin may be placed on these intersections as a visual aid. Stones adjacent to a coin do not have a liberty at the coin.

There are different ways to determine intersections occupied by coins:

  • Intersections are chosen (randomly or not) at the beginning of the game before either player takes a turn. A possible alternative is players take turns placing coins on the board.

  • An even number of coins is split between both players. The game begins with no coins on the board. Players may use a turn to place a coin on the board. A possible alternative is to allow spending a coin to remove a coin from the board.

  • (The two methods above may also be combined)

Coins may not be captured through liberty shortage. For scoring, coins do not contribute to territory. Normal scoring rules apply.

Since playing as Black might have the potential of being a significant advantage in this variant, players may use the “Pie rule” to determine who plays which color:

  1. Player A plays Black’s first move.
  2. Player B decides whether to be Black or White for the remainder of the game.
I have added the rules for the variant in the corresponding Wikipedia page!

Although I have not yet tried this variant myself (playing games in person is rare during Covid), I’m pretty sure that it has potential, due to its flexibility. I have taken the liberty to edit the Wikipedia entry for Go variants to add Coin Go. I hope this idea will take off!

Note that someone has already created a tool that can generate images of Go boards with removed intersections where coins would be placed. For example, here is what a 19x19 board with 10 “coins” would look like:

This could be renamed as ‘Gap Go’, or ‘The Floor is Lava’!

You can follow the discussions I started here:

Let me know if you give this variant a shot! 😄