Life and death, tesuji
Most games are decided not by territory but by whose group died.Counting liberties and eyes is the core tactic of go.
Two eyes
A group lives forever if it has two real eyes — two separate empty points inside it that the opponent cannot occupy (any stone of theirs there would be suicide). One eye, however big, does not save it: the group gets surrounded from outside and the eye is filled from inside.
A false eye looks like an eye, but one of the stones around it can be put in atari — and then you have to fill the point yourself.
The shape of the eye space
An empty space of three points in a row is alive or dead depending on one move: whoever plays the middle point first. The same goes for the bent three, the pyramid four and the bulky five. A straight four lives by itself: every move inside has an answer.
. . . . . .
X X X X X . X — a group;
X . . . X . three empty points:
X X X X X . the move in the middle decides everything
Atari and the ladder
Atari means a stone has one liberty left. A stone in atari that runs in a zigzag often ends up in a ladder: the opponent keeps putting it in atari,the chain stretches diagonally, and the stones die at the edge of the board. Before running, follow the ladder to the end — if there is no stone of yours on its path, don't run.
Tesuji
A tesuji is the precise move that solves a local problem. The most common:
- Net (geta) — a stone not in atari but on the escape route: the stones have nowhere to go.
- Snapback — give up a stone to capture more at once.
- Shortage of liberties — the opponent's group seems to have enough room, but its liberties are tight and it cannot play the move it needs without putting itself in atari.
- The vital point — play where the opponent wants to make the second eye.
Seki
Two groups without two eyes share liberties, and whoever plays there first dies. This is seki — both live. Under Japanese rules territory inside a seki does not count; under Chinese rules the stones in seki do count.
How to practise
Solve life-and-death problems, a few a day — short ones, 3–5 moves deep. On 9×9 the same shapes come up in every game.