Every go primer says corners first, then sides, then centre. It sounds like tradition. It is actually arithmetic.
The arithmetic of enclosure
To surround nine points of territory in the corner takes about six stones — the board's edges do two of the walls for you. The same nine points on the side takes about nine stones, and in the centre about twelve. Corners are simply cheaper.
That is the whole reason for the order. It is not that the centre is unimportant; it is that centre territory costs more stones to secure, so it comes later, once the cheap ground is taken.
Third line versus fourth line
A stone on the third line from the edge is aiming at territory: it is close enough to the edge to enclose points reliably. A stone on the fourth line is aiming at influence: it gives up some certainty near the edge in exchange for facing the centre.
Neither is better. A balanced opening mixes them. A position entirely on the third line ends up with solid but small territory; entirely on the fourth line ends up with grand-looking influence that never becomes points.
Corner points and what they mean
| Point | Character |
|---|---|
| 3-3 | Takes the corner territory immediately, gives the opponent outside influence |
| 3-4 | Slightly favours territory; the classic opening point |
| 4-4 | Favours influence and speed; easy to invade at 3-3 |
| 5-4 / 5-3 | Strongly influence-oriented, less common for beginners |
On 9×9, the 3-3 point and the centre dominate because the board is too small for influence to pay off. On 19×19 the 4-4 point is the most common modern choice.
Approach moves and extensions
Once corners are taken, the next moves are approaches — playing near an opponent's corner stone to stop it expanding — and extensions, which develop your own stone along a side. A useful rule for extensions: a two-space extension from one stone is safe; a three-space extension is loose and invites an invasion between them.
Big points versus urgent points
A big point is a large empty area worth occupying. An urgent point affects the safety of a group. Urgent beats big, always. Taking a fifteen-point area while your group gets surrounded is a losing trade even though the numbers look good.
Ask which groups are weak
Before playing a big open point, check every group on the board for both sides. If either side has a weak group, the move near it is nearly always more valuable.
Direction of play
The hardest opening idea. Every move faces somewhere, and it should face where you have potential and the opponent does not. Extending along a side where you already have a wall is efficient; extending toward the opponent's strength is not.
Practically: before playing, look at which side of the board has more of your stones and fewer of theirs. That is usually the direction.
A simple opening plan
- Take an empty corner.
- Take another, or enclose the one you have.
- Approach one of the opponent's corners.
- Extend along a side from your own strength.
- Then look for urgent points before big ones.