In gomoku, X moves first, and that first move is a real advantage: X is always one stone ahead in building lines. Many serious rule systems add restrictions for the first player to balance this. On this site, under both the Vietnamese blocked ends rule and freestyle, there are no such restrictions. That makes playing O against the computer a genuine challenge, and a very good one for improving your defence.
Why moving second is hard
Gomoku is a race to create a threat the opponent cannot answer. Being one stone behind means X usually gets the first forcing move. If you, as O, spend your early moves building your own separate formation, X simply builds faster and starts a forcing chain before you do.
The solution is not to race but to interfere. Your early stones should do two jobs at once: limit X's lines and start your own.
The opening as O
When the computer plays X, its first stone usually lands near the centre. Place your first stone right next to it, most often touching it diagonally. A diagonal touch blocks one of X's diagonals and leaves you room to grow along rows and columns.
For the next few moves, keep your stones close to X's stones. Every time X extends a line, your stone at its end limits it. Every time you place such a stone, look for a way to line it up with your earlier stones. Moves that both block and build are the whole art of playing O.
The middle game: survive the forcing chain
Sooner or later X will start making threats: an open three, then a four, then another three. Your job is to answer each one accurately and, whenever you have a choice of blocking points, pick the one that builds your structure. See counterattack from defence for the details.
Watch especially for the points where two of X's lines meet. Taking such a point before X uses it breaks two lines with one stone, and it is often the move that saves the game.
Striking back
X's forcing chain will eventually end with a quiet move, because there is a limit to how many threats any position contains. That moment is your chance. If your defensive stones have lined up well, you may have a four or an open three ready. Play it. Now X must answer you, and the initiative has changed hands.
From there, the same ideas as for X apply: chain forcing moves, keep fours in reserve for a double threat, and check before every move that X has no four of its own to play first.
The blocked ends rule helps O
Under the Vietnamese blocked ends rule, a five closed at both ends does not win. This gives O extra resources: each of your blocking stones permanently weakens X's line, and a second block at the far end kills it completely. As a result, O usually has more defensive resources under blocked ends than under freestyle. If O feels impossible at first, start with blocked ends.
Which level to practise at
Playing O is hard enough that you may want to drop one level from where you play as X. If you beat level 3 as X, try level 2 as O first. When you can win about half your games as O at a level, you have mastered that level for real.
What O teaches you
Players who practise as O become far better defenders, and good defence wins more games than any attack. They learn to see the opponent's lines early, to value every stone twice (once for blocking, once for building), and to recognise the exact moment when an attack runs out. Those skills make you stronger as X too.
A typical game as O
Here is how a successful game as O often unfolds. X opens in the centre. You touch its stone diagonally. X builds a two along a row; you place a stone at one end that also sits on your diagonal. X makes an open three; you block at the end nearer to your stones. X plays a closed four; you block the only open point. X then plays a quiet stone to connect two of its twos.
This is your moment. Look at your stones: the blocks you made at the end of the row, the diagonal stone and the four-block now sit close together. One more stone between them makes an open three. X must answer it. With the tempo you gained, you add a stone to a second line, and suddenly X is the one defending.
None of your moves in that sequence was spectacular. Every one of them simply did two jobs at once. That is how O wins.
Mistakes to avoid as O
- Starting your own formation far from X's stones. X builds faster and you never catch up.
- Blocking at the far end of a line out of habit. Choose the end that builds your stones.
- Making a three while X has an open three. X makes an open four and wins.
- Using your fours too early. You will need them when X's chain arrives.
Tracking your progress as O
Because games as O are harder, keep your expectations realistic. Winning one game in four as O at a level you beat easily as X is already good progress. If you sign in on the account page, your games are saved, and you can compare how long your games as O last over time. Longer games usually mean better defence, even before the wins start coming.
A simple O checklist
- Place your first stone touching X's first stone, usually diagonally.
- Keep your stones close to X's stones through the opening.
- Answer every four and open three, choosing the block that builds.
- Take X's crossing points before they become landing points.
- Strike as soon as X plays a quiet move.
Frequently asked questions
Is X really stronger in gomoku?
Yes. Moving first gives X a real advantage, which is why many rule systems restrict the first player. This site does not.
Where should O place the first stone?
Next to X's first stone, usually touching it diagonally.
How can O ever win?
By blocking in ways that build its own lines, surviving X's forcing chain, and attacking when X plays a quiet move.
Is O easier under the blocked ends rule?
Usually yes, because each block permanently weakens X's line.
Should I play at a lower level as O?
Often, yes. Drop one level and move up once you win about half your games.
