How to play Go

Go is an ancient strategy game from East Asia, played with black and white stones on the crossings of a grid. Players take turns placing one stone at a time, and once a stone is on the board it never moves. The aim is to fence off more of the board than your opponent, capturing any enemy stones you completely surround along the way.

The rules take a few minutes to learn, yet the game is famous for its depth: every stone can serve attack and defence at once, and a battle in one corner can decide a fight on the other side of the board. Nothing depends on luck. Here you play Black and the computer plays White.

How to play on skill.games

In the settings popup choose a difficulty (Easy, Normal, Hard or Crazy) and a Board: 9x9, 13x13 or 19x19. Press PLAY. You are Black and you place the first stone.

• Placing a stone: on the 9x9 board, tap an empty crossing. On 13x13 and 19x19 the crossings are small, so the first tap aims (a ghost stone appears and the status says TAP AGAIN TO PLACE) and a second tap on the same spot places it. Tap somewhere else to aim again.
• Passing: tap the PASS button when there is nothing useful left to play. When the computer passes, the status reads BOT PASSES - PASS TO FINISH.
• Warnings: your groups that are down to their last liberty pulse red with the message ATARI! YOUR STONES CAN BE TAKEN. An illegal point is refused with a short note, such as KO - PLAY ELSEWHERE FIRST or NO LIBERTIES THERE.
• Score line: during play it shows how many stones each side has captured; during the final count it switches to points.

The menu button in the top-left corner pauses the game, with options to resume, start a new game or turn the sound off. The game is saved at every turn, so you can close the page and CONTINUE later.

When the game ends, the results screen shows the final points (yours, and the computer's including its komi), the winning margin, the stones each side captured and the number of moves, together with your statistics: wins, losses, win rate, current streak and best streak. Each board size keeps its own record per difficulty.

Rules

The board. Stones go on the crossings of the lines, not inside the squares. The board starts empty. Black plays first, then the players alternate, placing one stone per turn on any empty crossing.

Liberties. The empty crossings directly next to a stone (up, down, left and right) are its liberties. Stones of the same colour that touch along the lines form a group and share their liberties.

Capturing. When you place a stone that takes away the last liberty of an enemy group, that whole group is captured and removed from the board. A group with only one liberty left is said to be in atari.

No suicide. You may not place a stone where your own group would have no liberties, unless that move captures enemy stones and so gains liberties.

Ko. You may not immediately recapture a single stone that has just captured a single stone of yours, because that would repeat the position forever. Play somewhere else first; on the next turn the recapture is allowed again.

Passing and the end. Instead of placing a stone you may pass. When both players pass one after the other, the game ends.

Counting. The board is then counted automatically. Stones that could not survive (dead stones) are recognised and removed first. Each player scores:

• one point for every stone of theirs on the board, plus
• one point for every empty crossing surrounded only by their stones.

This method is known as area scoring. White receives 6.5 extra points, called komi, to make up for Black's advantage of moving first. The higher total wins. Because of the half point, a game can never be drawn.

Strategy tips

• Corners first, then sides, then the centre. A corner is enclosed by two edges, so it takes the fewest stones to claim territory there. The centre is the hardest area to secure.
• Count liberties in every fight. When two groups are touching, the one with more liberties usually wins the race to capture. Before you attack, count both sides.
• Answer atari. When one of your groups is put in atari, extend it to gain liberties, connect it to a friendly group, or decide to give it up, but do not ignore it by accident.
• Make two eyes. A group that surrounds two separate empty points can never be captured, because the opponent cannot fill both at once. Secure two eyes for groups under attack.
• Stay connected. Two weak groups are a burden; one strong group is an asset. When the computer tries to cut your stones apart, connecting is often the best answer.
• Don't chase stones that are already dead. Adding more stones inside your own territory costs nothing in area scoring, but every tempo spent there is a move not played on the open board.
• Pass only when the borders are closed. If there is still a gap in a wall between your area and the computer's, play it first. Passing too early hands over points.

Difficulty levels

The computer chooses moves by trying out many possible continuations of the game from the current position and seeing which moves tend to lead to a win. The higher the level, the more continuations it tries and the more time it spends.

• Easy: tries only a small number of continuations and often picks a less promising move. Green rings show you where a computer group in atari can be captured.
• Normal: tries several times more continuations and usually picks one of its best-looking moves. The green capture hints are still shown.
• Hard: tries many more continuations and always plays the move that looked best. No hints.
• Crazy: spends the longest time and tries the most continuations of all. No hints.

Modes

The Board setting chooses the size:

• 9x9: the quick board, a game takes a few minutes. Good for learning, and fights start straight away. One tap places a stone.
• 13x13: more room to build territory and plan; tap once to aim, tap again to place.
• 19x19: the full traditional board, for long games with many separate fights. Tap once to aim, tap again to place.