Kevin HY Hau - Hello World 👋

📖 Rules of Go (圍棋)

Go is a two-player game from China, more than 2,500 years old. Black and White take turns placing a stone on an empty crossing of the lines. Stones never move once placed, but they can be captured. At the end, the player who controls more of the board wins.

The basics

• Black plays first (unless there is a handicap, then White starts). Each turn you either place one stone on an empty crossing, or pass.
• Liberties: the empty crossings straight next to a stone (up, down, left, right) are its liberties. Stones of one colour that touch in a line form a group and share all their liberties.
• Capture: when you take away a group's last liberty, the whole group is removed from the board and kept as prisoners.
• No suicide: you may not play a stone that leaves its own group with no liberties, unless that move captures enemy stones (they are removed first, which gives you liberties).
• Ko and repeats: you may not make a move that brings the board back to any earlier position (this is “positional superko”). The simple case is a ko: after you capture one stone, your opponent cannot immediately capture back; they must play elsewhere first.
• Eyes: a group with two separate eyes (single empty points it surrounds) can never be captured, because you cannot play in an eye without suicide. This is how groups live.

Ending and scoring

• The game ends when both players pass in a row.
• Then the dead stones are removed: stones that could not avoid capture. The game makes a guess and marks them with a ✕; tap a group to mark or unmark it if you disagree, then press Done, score it. (If you cannot agree, press Keep playing.)
• Area scoring (the Chinese way): your score is the number of your stones on the board plus the empty crossings that only your stones surround. White also gets komi, extra points to make up for Black moving first (7 on 9×9, 7.5 on 13×13 and 19×19 by default; 0.5 with handicap stones). Higher total wins.
• You can also resign at any time.

Board sizes

Handicap

If one player is much stronger, the weaker player takes Black and starts with 2 to 9 stones already on the board (on the marked star points); White then plays first. Handicap stones can be used on 9×9, 13×13 and 19×19 boards.

A few tips

• Take the corners first, then the sides, then the middle: corners are the easiest places to make territory.
• Connect your stones; cut the enemy's. Stones with few liberties are weak.
• Do not fill in your own territory. Make two eyes to keep a group alive.
• When your opponent plays next to your stone, do not just follow: think about where the game is biggest.

How to use this game

• Mouse: click an empty crossing to play. Phone or touch: press and drag; the stone appears a little above your finger so you can see it; let go, then press Place stone. (There is a switch in Settings to do the same with a mouse.)
• Settings: board size, handicap, your colour, the computer's level, komi, board and stone styles, coordinates, last-move marker.
• Hint thinks for a moment and shows a good point. Undo takes back your move and the computer's reply. A small line under the board shows the computer's own estimate of who is ahead.
• How the computer thinks: it plays thousands of quick random games from the position and picks the move that did best (Monte Carlo tree search). It plays a decent game on 9×9, but it is a casual opponent on 13×13 and still weak on 19×19.
• Not included: Japanese (territory) scoring, seki handling in the dead-stone guess (you can fix it by tapping), and online play.