Go

Two players, Black and White, take turns placing one stone on an empty point where the lines cross. Black goes first. Stones never move. The goal is to surround more of the board than your opponent.

Liberties and capturing

Stones of one colour that touch along the lines form a group. The empty points next to a group are its liberties. When you fill a group's last liberty, you capture it: its stones come off the board.

You may not play a stone that would have no liberties, unless it captures something. You also may not make a move that brings back a whole-board position that has happened before. (This stops two players capturing one stone back and forth for ever.)

Passing and the end

Instead of placing a stone you may Pass. When both players pass in a row, the game ends.

Then any stones that could not avoid capture are marked dead. The computer suggests which ones; tap a group to switch it between dead and alive, then tap Count.

Online, nobody has to agree on the marks: dead stones are marked for you and the game is counted as soon as you both pass. If a group is in doubt, capture it before you pass (inside your own area that costs nothing).

Scoring

Your score is your stones still on the board plus the empty points surrounded only by your stones. Dead stones are removed first and their points go to whoever surrounds them. White gets 7.5 extra points for moving second, so there are no ties. The higher score wins.

Tips

• A group with two separate empty points inside it (two “eyes”) can never be captured.
• Corners are easiest to claim, then the edges, then the middle.
• If a group is down to one liberty, save it by adding a stone there, or let it go and play elsewhere.

The last stone played has a small ring. On the 13 × 13 board, tap once to preview a stone and again to place it. Undo, Resign and the other options are in the ⋯ menu.