Enhanced Go

Every rule of Go, plus one: on your turn you may place n stones at once by first removing n² of your own. A sudden wall can win a fight, if you can afford it.

Players: 2 players
Modes: Two players on one device, on a 9×9, 13×13 or 19×19 board

Play Enhanced Go

How to play

Enhanced Go is Go with one extra kind of turn. If you know Go, you know almost everything already; if you don't, the tutorial on the Play page starts from the beginning.

On your turn, do one of three things:

Ordinary turn: place one stone on an empty point. It costs nothing.
Special turn: place n stones at once (n is 2 or more) by removing n² of your own stones from the board. Two stones cost four, three cost nine.
Pass. When both players pass in a row, play stops and the board is counted.

Taking a special turn on the Play page

Press Special. Choose n with the minus and plus buttons.
In the Pay step, choose your own stones to remove. In the Place step, choose where the new stones go. Switch between the steps whenever you like; the counts (for example “place 2 of 2, remove 4 of 4”) show what is still missing.
Once the choice is complete, the panel says whether the turn is allowed and what it would capture. Press Commit turn to play it, or change your choices, or Cancel special turn. Nothing on the real board changes until you commit.

Try it

Each example below is live: build the special turn yourself, or press Show me. The mistake buttons fill in a tempting wrong answer so you can see what the rules do with it.

Two stones in one turn

The White stone at C3 has two liberties, D3 and C2. In ordinary Go you'd fill one, and White would answer. Here you can fill both at once by paying four of your own stones. Try to capture C3 this turn.

Build the special turn on the board, then commit it.

n = 2

Place 2 stones by removing 4 of your own. You have 6 on the board, so n can go up to 2.

Place 0 of 2, remove 0 of 4

Two eyes aren't safe

In ordinary Go, a group with two separate eyes can never be captured: a stone in either eye would be suicide. With a special turn, both eyes can be filled at the same moment. Capture the White group.

Build the special turn on the board, then commit it.

n = 2

Place 2 stones by removing 4 of your own. You have 20 on the board, so n can go up to 4.

Place 0 of 2, remove 0 of 4

Three eyes cost nine stones

This White group has three eyes: B6, D6 and F6. Two stones won't do, and three stones cost 3² = 9. Black has 16 stones, so n can go up to 4. Capture the group without weakening your wall.

Build the special turn on the board, then commit it.

n = 2

Place 2 stones by removing 4 of your own. You have 16 on the board, so n can go up to 4.

Place 0 of 2, remove 0 of 4

Full rules

This is the current ruleset of Enhanced Go. Everything not mentioned works as in ordinary Go.

The special turn. A special turn places n stones by removing n² stones. The payment comes from your own stones only.
Ordinary turns stay free. An ordinary turn places one stone and removes nothing. Special turns use n ≥ 2.
What you can afford. n is limited by having at least n² of your own stones on the board at the start of the turn.
Order. Remove first, then place. You may place on points you just vacated.
Resolution. All n stones land at once. Then opponent groups with no liberties are captured. Then the turn is refused if any of your own groups has no liberties (suicide). Ordinary turns follow normal Go capture and suicide rules.
Payment. Stones placed this turn can't be used to pay.
Positional superko. No turn may recreate any earlier whole-board position.
Ending and scoring. Two consecutive passes end play. Area scoring, with komi 7.5 for White. Board sizes 9×9 (the default), 13×13 and 19×19.

The scoring phase (part of the current ruleset)

Dead stones are settled by agreement, not by playing them out. After two consecutive passes, play stops and:

Both players mark the groups they agree are dead. Marking a stone marks its whole group; marking it again unmarks it. Dead stones are counted as empty points.
Each player's score is their stones on the board plus the empty points that only their stones reach. White adds 7.5 komi, so there are no ties.
The score is final when both players accept the same marking. Changing the marking withdraws any acceptance already given.
Either player can resume play instead of accepting. The marks are cleared and play goes on; two more consecutive passes return to scoring.

We chose this agreement phase over Tromp–Taylor counting (where every stone left on the board counts as alive) because it lets games end when the outcome is clear, as people actually play Go.

Details this implementation decides

The approved ruleset doesn't spell these out, so this implementation settles them as follows:

Passing is always allowed. A pass leaves the board as it is, so it can't “recreate” an earlier position.
Superko looks only at the board. Whose turn it is doesn't matter, and the starting position counts. A special turn can recreate an earlier position too (by paying with stones and putting some straight back), and is refused if it does.
Suicide is refused in ordinary turns as well, as in most Go rulesets: a stone that captures nothing and leaves its own group without liberties can't be played.
After resuming play, the player whose turn it would have been moves next: the opponent of whoever passed second.
Neutral points. An empty area that touches both players' living stones, or none, counts for nobody. This covers seki.

Not in the current ruleset

Resignation, handicap stones and time limits aren't part of the approved rules, so the Play page doesn't offer them. There is no undo once a turn is committed.

Credits and licensing

Enhanced Go was invented by Ian Joiner.
Implementation by Peace Cat Games.

Go is a traditional game, more than two thousand years old, that belongs to everyone. Enhanced Go, invented by Ian Joiner, adds the special turn to it. The rules engine, board and examples here are newly written by Peace Cat Games; the board is drawn in code, with no third-party artwork.

This is local play for two people on one device. There is no computer opponent and nothing here uses a Go engine; we know of no Go engine that supports special turns. We make no claims about how well computers would play this variant.