Go 19x19
The full board is Go as it is actually played, and a game is two to three hundred moves. That is days rather than an evening, so pick a move deadline that suits that. The rules are the same five as on any board. Two passes stop the game rather than ending it, which surprises everybody once.
The rules
- The board is a grid of lines, and a stone goes on an INTERSECTION where two lines cross, not in a square. The edges and corners are points too.
- Black plays first. After that you take turns, and you may pass at any time instead of playing.
- A stone or a solid group of stones is captured when the last empty point next to it is filled. Those empty points are called liberties, and a group with no liberties comes off the board.
- You cannot play a stone that would leave your own group with no liberties. The one exception is that if the same move captures something, it is fine: the capture happens first and gives you the liberty back.
- You cannot immediately recapture in a way that repeats the position that was on the board a move ago. That is the ko rule, and it is what stops the same two stones being taken back and forth forever. Play somewhere else first.
- The 19x19 board has 361 points and nine marked star points. A game is two to three hundred moves, so a long move deadline is the sensible choice: the shortest this board offers is an hour.
How a game ends, which is not when you think
- TWO PASSES DO NOT END THE GAME. They stop play, which is not the same thing. Every other game on this site is over at that point; this one is not.
- What happens next is that the two of you agree which stones are dead. A stone is dead if it could not escape, even though nobody has bothered to actually capture it. Those stones come off and count as prisoners.
- One of you proposes a set of dead stones and presses done; the other accepts, or disagrees and sends the game back to the board to be played out. You get three disagreements.
- If you still cannot agree after that, the game is counted a different way, by area, which needs nobody to agree anything. The number comes out within a point or so of the same.
- A game also ends if somebody resigns, or if a move deadline passes without a move.
How it is counted
- Your score is the empty points you have surrounded, minus the stones of yours your opponent has captured.
- An empty region surrounded by both colours belongs to nobody. Those points are called dame and they are worth nothing, so filling them in at the end gains you nothing and costs you nothing.
- PRISONERS COUNT AGAINST YOU, which is the part that catches people out. Playing an unnecessary stone inside your own territory fills one of your own points and gives your opponent nothing to capture; playing a stone that gets captured hands them a point as well as the territory.
- White gets 6.5 points of komi for going second. The half point means a game can never be tied.
Worth knowing on the full board
- The opening goes to the corners, then the sides, then the middle, because that is the order in which territory is cheap to make.
- Several fights run at once and most moves are a choice about which one to answer. Leaving a fight to take a bigger point elsewhere is most of the game.
- A game this long is a game you come back to. The deadline is per move, not per game.
About the computer opponent on this board
- IT IS WEAK, AND IT IS WEAKEST HERE. The opponent reads the position by playing out thousands of random finishes and counting how many it wins. That works on a small board. On 361 points it is not enough search to play well, and a move has to be produced inside the time it takes to load a page.
- So the bot on this board is a beginner, and a hint is the best move that beginner has. If you want a real game on the full board, play a person.
- On the 9x9 board the same opponent is a good deal stronger, because the same amount of thinking goes a lot further on 81 points.
Go is counted the Japanese way on this site: territory you surround, less the stones your opponent took from you. Some parts of the world count by area instead, which counts your stones as well as your territory and usually gives the same winner by a slightly different margin.