6neighbours for every cell away from the edge, where a Go point has four.
3stones capture a lone stone in the open. Two do it on the edge, one in a corner.
2empty cells that touch each other, a liberty pair, keep a group alive on the board. One liberty is not enough.
Play
Choose how you want to play, then set up the board.
Online game
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BlackBlack0
WhiteWhite0
Black to play
Move 0 of 0
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Game over
Black
White
Faded stones are counted as dead. If that looks wrong, tap a group to change it.
The link is the game. Open it again in this browser to come back to your seat. A game is removed after 2 days without a move.
Learn
The whole rule set, one idea at a time. Boards marked Try it are live: tap a cell and the game's own rules engine answers.
The game
Two players, Black and White, take turns placing one stone on any empty cell. Black goes first. Stones never move. They stay where they are put unless they are captured and taken off the board.
The player with more points at the end wins. You get a point for every empty cell you have surrounded and a point for every stone you have captured. White also gets extra points for moving second, called komi. Komi is currently 6, similar to Go.
The board is a hexagon, and its size is the number of cells along one side: 5 per side has 61 cells, 7 per side has 127.
Groups
Stones of one colour that touch each other form a group. A group is captured or survives as a whole, so joining your stones together is how you make them strong.
Three groups: a black group of three, a white group of two, and a black stone on its own.
Liberty pairs
An empty cell next to a group is one of its liberties. In HexGo one liberty is not enough. A group needs a liberty pair: two empty cells that touch each other and both touch the group.
After every move, a group with no liberty pair is captured and removed, unless it has eyes. Eyes come later.
The two marked cells touch each other and both touch the white stone. That is a liberty pair, so White stays.Try it Black to play. Capture the white stone.
Edges and corners
A stone on the edge has fewer neighbours, so it has fewer ways to make a pair. Two stones are enough to capture a stone on the edge. One stone can capture a stone in the corner.
Try it Black to play. Capture the stone on the top edge.Try it Black to play. Capture the corner stone with one move.
Eyes
An eye is an empty area closed in by a single group: every stone around it belongs to that group. The empty cells inside are its eye cells, and they are counted across all of the group's eyes.
A group with at least two eye cells, a pair of eyes, stays on the board even when it has no liberty pair. The shape of its eyes decides how safe it is.
Try it One eye cell. Black to play: capture the white ring.Try it A pair of eyes keeps White on the board, but only just. Black to play: capture.Try it Three eye cells in a row. Black to play: try to capture.
Eyes on the edge
The edge of the board works as a wall. An area closed in by your stones and the edge is an eye, the same as one ringed completely by stones.
That makes eyes much cheaper at the edge. Five stones hold three eye cells there. In the middle of the board it takes ten.
Try it Two one-cell eyes on the top edge. Black to play: capture.Try it Five white stones and the edge hold three eye cells. Black to play: try to capture.
Kinds of eyes
The same shapes turn up again and again, in the middle of the board and on the edge. In each board below White has no liberties left outside, apart from the one-cell eye, which needs a liberty pair to be on the board at all. marks the eye cells.
One cell
Needs a pair
Not enough by itself. The group lasts only while it keeps a liberty pair outside.
Centre, 6 stonesEdge, 4 stones
Two cells together
One move captures
A stone in either cell breaks the pair of eyes, and the group comes off.
Centre, 8 stonesEdge, 5 stones
Two one-cell eyes
One move captures
Safe in Go, not here. Filling one eye breaks the pair.
Centre, 11 stonesEdge, 6 stones
Three in a line
Safe
Any stone played inside leaves a pair of eyes and has no liberty pair of its own, so the move is not allowed.
Centre, 10 stonesEdge, 5 stones
Three, bent
Safe
The same as a straight line, as long as the two end cells do not touch.
Centre, 10 stonesEdge, 5 stones
Two cells and one apart
Safe
Three eye cells in two eyes. A stone in either eye still leaves a pair of eyes, so it is not allowed.
Centre, 13 stonesEdge, 6 stones
Three one-cell eyes
Safe
Fill any one of them and a pair of eyes is left, so no stone can go in.
Centre, 13 stonesEdge, 9 stones
Three in a triangle
Dead
The triangle of death. All three cells touch each other, and that is the weakness.
Centre, 9 stonesEdge, 6 stones
The triangle of death
Three eye cells that all touch each other look like the safest eye of the three-cell shapes. They are the only one that dies. A stone played inside a line of three has no liberty pair, so it is not allowed. A stone played inside a triangle touches the two other cells, and those two touch each other. That is a pair, so the move is legal.
Black plays inside. The two eye cells left are a liberty pair for the black stone, so it stays for now.White captures it. That leaves White with an eye of two cells together.Try it Black to play: finish it.
White does no better by leaving the first black stone alone. Black adds a second stone inside, White is down to one eye cell, and the whole group is captured. Once a group surrounded on the outside depends on a triangle, it cannot be saved, so give your eye a different shape while you still can.
Who is captured first
After a stone is placed, the board is checked in a fixed order.
The opponent's groups are checked. Any with no liberty pair and no pair of eyes are removed.
Then the mover's own groups are checked. If one of them would be captured, the move is suicide and is not allowed.
So a stone that looks doomed is legal when it captures something first. One more detail: a stone played inside an eye that cannot survive there does not break the eye open. The cell it sits on stops counting, but the rest of the eye still does.
Try it White's corner eye has two cells. Black to play: capture.
No repeats
A move may not bring back an arrangement of the whole board that has already happened in the game. This stops two players capturing back and forth for ever. Go players call the situation ko.
Ending and scoring
When you see nothing useful left to play, pass. Two passes in a row end the game. Then the score is counted.
Stones that could not avoid capture are taken off as dead. They count as captures for the other player.
Each player gets one point for every empty cell in an area bordered only by their own stones, and one point for every stone captured.
White adds 6 points of komi for moving second.
In computer test games with no komi, Black finished about 5 points ahead on boards of 5 and 6 per side and about 8 ahead on 4 per side. Komi is set at 6 for now, similar to Go. Because it is a whole number, a game can end in a draw.
A finished game. Small dots mark each player's territory.
If you know Go
Go
HexGo
Neighbours of a point
4
6
To stay on the board
One liberty
A liberty pair, or a pair of eyes
Stones to capture one stone
4 in the open, 3 on the edge, 2 in the corner
3 in the open, 2 on the edge, 1 in the corner
Two one-point eyes
Safe for good
Can be captured. Three eye cells in a line are safe, three in a triangle are dead.