Strong Go players often talk about shape: "that is good shape", "that is heavy", "that is an empty triangle". They also talk about tesuji, the clever moves that win local fights. Both words describe qualities you can learn to see, and seeing them improves your play faster than memorising sequences.
This article explains the most common shape terms and what tesuji means.
What shape means
Shape is about how efficiently a group of stones works. Good shape:
- uses few stones to cover a lot of space,
- has few cutting points or weaknesses,
- gives the group room for eyes or easy connection to friends.
Bad shape does the opposite: it uses many stones for little effect, leaves weaknesses, or crowds the group so it cannot make eyes.
Shape matters because every move is a resource. A move spent fixing bad shape is a move not spent claiming territory or attacking.
Bad shape: the empty triangle
The best-known bad shape is the empty triangle: three stones of one colour forming an L, with the fourth corner of the little square empty. It looks solid, but it is inefficient: the three stones have fewer liberties than three stones spread more loosely, and they cover less space.
The empty triangle is not always wrong. Sometimes it is the only way to connect or to make a key liberty. But when you see yourself about to play one, stop and look for a more efficient move.
Bad shape: heavy groups
A group is heavy when it has many stones, no clear way to live, and too much invested to give up. Heavy groups become targets: your opponent attacks them and gains profit while you defend. The opposite is light: a group that can easily give up a stone or two and settle quickly.
Good shape: the tiger's mouth
The tiger's mouth is a shape of three stones around an empty point, like an open mouth. If your opponent plays into the mouth, their stone is immediately in atari and can be captured. It protects a cutting point efficiently and is also the basis of the hanging connection.
Good shape: the bamboo joint
The bamboo joint is two pairs of stones side by side with a gap between them. It cannot be cut: if your opponent plays in one gap point, you play the other. It is a strong and efficient way to extend under pressure.
Good shape: the ponnuki
When you capture a single stone with four of your own stones around it, the diamond-shaped result is called ponnuki. It is famous as extremely strong shape, because it has no weaknesses and radiates influence in every direction. An old proverb values it highly in the opening.
Good and bad extensions
- One-point jump: two stones on the same line with one point between them. Hard to cut and flexible.
- Two-point jump: faster but thinner; easier to cut when the opponent is nearby.
- Knight's move (keima): efficient for moving quickly, but can be cut with two moves.
- Large knight's move: faster still, but thin.
Choosing the right extension is part of shape judgement: fast and thin when you are safe, slow and solid when you are under attack.
Tesuji
A tesuji is a clever, often surprising local move that achieves the best result. It might capture stones that seemed safe, save a group that seemed dead, or connect stones that seemed separated. Examples of common tesuji ideas:
- Snapback: letting your opponent capture a stone so you can capture more back. See liberty, atari and snapback.
- Throw-in: sacrificing a stone inside the opponent's shape to reduce their liberties or make a false eye.
- Placement: playing at the vital point inside an eye space to prevent two eyes. See eyes and eye space.
- Wedge: playing between two opposing stones to separate them.
The opposite of tesuji is zokusuji, an obvious-looking move that is actually inferior. Many beginners' moves are zokusuji: natural, but not the best.
How to learn shape and tesuji
- Look at your stones after each fight. Did you end up with empty triangles and heavy groups, or with light, efficient shape?
- Ask why strong moves work. When an opponent surprises you with a good move, find out what made it effective.
- Solve small problems. Tesuji are learned through practice positions; each one teaches a pattern that reappears in games.
- Play many small games. On 9×9, shape problems and tesuji come up constantly.
On this site, you can play the computer on the home page on 9×9 or 13×13 and people on the online page. If you sign in on the account page, your games are saved; replaying them and marking your bad shapes is a quick way to improve.
Shape proverbs
Go has many proverbs about shape. Two of the most useful:
- "Play the empty triangle only when you must" (in various wordings): avoid inefficient shape unless there is a reason.
- "Strike at the head of two stones": when two of your opponent's stones are lined up, playing just ahead of them often creates bad shape for them and good shape for you.
Proverbs are guidelines, not laws, but they capture patterns that experienced players have seen many times.
Recognising shape at a glance
Shape judgement becomes fast with experience. Strong players can often tell that a move is poor shape before they have read anything, just from how the stones look. You can build this intuition deliberately. When you review a game, pause after each fight and look only at the stones, not the result. Which stones are clumped together? Which leave gaps your opponent could use? Which look light and efficient?
Over time you will start to feel discomfort when you see an empty triangle or a heavy lump, and satisfaction when you see a bamboo joint or a tiger's mouth in the right place. That feeling is valuable, because it lets you skip obviously bad moves and spend your reading time on the few good candidates. It is not a replacement for reading, but it makes reading far more efficient.
Frequently asked questions
What is an empty triangle?
Three stones forming an L with the fourth point empty. It is usually an inefficient shape.
What does tesuji mean?
A clever local move that achieves the best result, often surprisingly.
What is a heavy group?
A group with many stones, no clear life and too much invested to abandon. It becomes a target.
What is ponnuki?
The diamond shape left after capturing one stone with four stones around it. It is very strong.
How can I improve my shape?
Review your games and look for empty triangles and heavy groups, and study why efficient shapes work.
