Go

Weiqi 圍棋 · Baduk · area scoring, komi 7.5

Black to move

0Blackcaptures

0Whitecaptures

Opponent

Show territory estimate Show move numbers Show coordinates

Rules

Players take turns placing one stone on an empty intersection. Black moves first. Stones never move once placed.
Stones of one colour joined along the lines form a group. The empty points next to a group are its liberties.
A group with no liberties left is captured and taken off the board. A group with one liberty left is in atari.
You may not play a stone that would have no liberties (suicide), unless it captures something first.
Ko: you may not play a move that recreates an earlier board position. After your opponent takes a ko, play elsewhere first.
You may pass instead of playing. Two passes in a row end the game.
Counting (area scoring): dead stones are removed, then each player scores one point per stone on the board plus one per empty point they surround. White gets 7.5 komi for moving second. Higher score wins.

Tips for beginners

Corners, then sides, then centre. Territory is cheapest to surround in the corners.
Two eyes live. A group with two separate empty points inside it can never be captured.
Watch your liberties. When a group is down to one or two liberties, add stones or capture a neighbour.
Don't cling to lost stones. Adding to a dead group only makes the loss bigger.
Start on 9 × 9. Games take ten minutes and teach the same ideas.

How the computer plays

Monte Carlo tree search. It plays thousands of quick games from the current position and favours the moves that win most often.
RAVE. Moves that did well anywhere in those games get credit early, so the search finds good shape faster.
Realistic quick games. Each quick game first answers the last move: capture a group in atari, save its own group by capturing or running, then play a known good shape (hane, cut, edge block) nearby. Only then does it play at random. It never fills its own eyes and avoids self-atari.
Ladder reading. It reads ladders to the end. It won't run with stones that are caught in a ladder, and it looks for ataris that capture in one.
Shape and opening sense. It prefers empty corners, then the third and fourth lines, and moves close to the last one played.
Keeps its reading. The analysis from its last turn carries over to the next move, and it stops early when one move is clearly best.
Levels. Easy plays a few hundred quick games and picks loosely. Medium thinks for 1.5–2.5 seconds and Hard for 4–6, longer on bigger boards.