A group needs two eyes to live — but most groups do not have two finished eyes. Instead they have an eye space: an enclosed empty area that might become two eyes. Whether it can depends on the shape of that space, and very often on a single point called the vital point. This article explains the basic eye shapes every Go player should know.
Eye space
The eye space of a group is the empty area it surrounds. If the space is big enough and shaped well, the group can divide it into two eyes. If it is small or badly shaped, the opponent can prevent that. The key question is always: can this space become two separate eyes, whoever moves first?
One and two points
- One-point space: one eye. Not enough by itself.
- Two-point space (two points next to each other): still only one eye. The opponent can play inside, and the group cannot divide the space.
A group whose only eye space is one or two points is dead unless it can connect out or make another eye elsewhere.
Three points: straight three and bent three
Three-point spaces are the first where the vital point appears.
- Straight three: three empty points in a row.
- Bent three: three empty points in an L-shape.
In both shapes, the middle point is the vital point. If the group's owner plays there, the space is divided into two separate one-point eyes, and the group lives. If the opponent plays there first, the group can make only one eye, and it dies.
Check it: if Black plays b1, the black group surrounds a1 and c1 separately — two eyes. If White plays b1 first, White's stone has liberties at a1 and c1, and Black cannot split the space; whatever Black does, only one eye remains.
Why "whoever moves first" matters
For shapes like straight three and bent three, the result depends on who plays the vital point first. That makes these groups unsettled: if it is your turn and your group is unsettled, making it safe is usually urgent. If it is your opponent's group that is unsettled and it is your turn, playing the vital point may kill it.
Larger spaces
Some larger shapes are alive no matter who moves first, because they can always be divided into two eyes. Others, like certain four-, five- and six-point shapes, have a vital point just like the three-point shapes. Learning them one at a time is part of the study of life and death (sometimes called tsumego).
General rules of thumb:
- Longer straight lines of empty points on the edge are usually alive once they reach four points in a row, because they can always be split.
- Compact, rounded shapes often have a central vital point that the opponent can occupy.
- Corners are special: the corner can make some shapes weaker than they look.
When in doubt, read it out: imagine both players' best moves and see if two separate eyes can be made.
Reducing eye space from outside
The opponent does not only attack from inside. Pushing along the edge or placing stones at the boundary can shrink an eye space until it becomes a dead shape. A five-point space can become a three-point space after two outside reductions — and then its vital point decides everything.
Practical habits
- Know your group's eye space. Count how many empty points it encloses and what shape they make.
- Take the vital point in time. If your group depends on one point, play it when you have the chance.
- Attack the vital point. When your opponent's group has a small, unsettled space, play the vital point before they do.
- Don't let your space be reduced cheaply. Protect the edges of your eye space when the opponent pushes in.
Practise
Build small groups in the corner in games against the computer on the home page and pay attention to the shape of their eye space. When a group dies, replay the end and find the vital point that decided it. Against people on the online page, sign in on your account so you can replay games later.
Related: two eyes to live, false eyes, corner life and death basics, how to study life and death.
Thinking about the bent three
The bent three works exactly like the straight three: three empty points, this time forming an L. The corner point of the L is the vital point. If the group's owner plays there, the two ends of the L become two separate eyes. If the opponent plays there first, the space cannot be divided. Beginners sometimes play on one of the ends instead; that leaves a two-point space next to the stone, which is only one eye.
Four-point shapes in brief
With four empty points, the shape matters a great deal. Four points in a straight line on the side can always be split into two eyes, whoever moves first, so such a group is alive. A compact square of four points, on the other hand, cannot be split at all: it is one eye, however it is played. Other four-point shapes, like a T-shape, have a vital point in the middle, just like the three-point shapes. You do not need to memorise a table; read each shape out, asking "if the opponent plays here first, can I still make two separate eyes?"
Why this knowledge saves moves
Knowing which shapes are alive saves you from two opposite mistakes: adding unnecessary defensive stones to a group that was already safe, and ignoring a group that looked safe but had a vital point. Each of those mistakes costs a move, and on a small board a single move often decides the game.
Frequently asked questions
What is a vital point?
A point in an eye space that decides whether the group can make two eyes. Whoever plays it first usually decides life or death.
Is a straight three alive?
Only if its owner plays the middle point. If the opponent plays there first, it cannot make two eyes.
Are two empty points next to each other two eyes?
No. They form one eye space of two points, which is only one eye.
Do bigger eye spaces always live?
No. Some larger shapes also have a vital point. Reading them out is the safest approach.
Why are corners tricky for life and death?
The corner changes how eye shapes behave, so a shape that is alive on the side may be weaker in the corner.
