When you play gomoku against the computer on the home page, there is an undo button. It takes back your last move, and the computer's reply, so you can try something else. Used carelessly, undo becomes a crutch: you never feel the consequence of a mistake, so you never learn to avoid it. Used well, it is one of the best training tools available, because it lets you replay the critical moment of a game as many times as you like.
What undo does
Undo returns the board to the moment before your last move. If the computer has already replied, that reply is taken back too, so it is your turn again. You can press it several times to step further back. Undo is available only in games against the computer; online games against real people have no take-backs, just like a game across a table.
The two ways to use undo
Rescue undo is pressing it the moment you see you have made a mistake, then playing a better move and carrying on. It feels good and keeps the game going, but the lesson is shallow: you did not have to think about how to survive the mistake, and the game you finish is not really the game you played.
Review undo is finishing the game normally, win or lose, and then stepping back through it to find where things went wrong. It is slower and less comfortable, but it builds real understanding.
Most players improve faster using mostly review undo, with rescue undo reserved for genuinely accidental taps, such as a stone placed on the wrong point by a slip of the finger on a phone.
A review routine that works
After a lost game:
- Step back to the move where the computer's winning double threat landed.
- Step back further, one move at a time, until the landing point was still empty and you could have occupied it. That is the real mistake.
- Replay from that point, occupying the landing point, and see what happens. Often the game continues for many moves, which shows how much one stone mattered.
- Say out loud, or write down, what you missed: a diagonal, a split three, a crossing point, a four you forgot.
After a won game, do the reverse: find the move where your winning shape first became possible, and ask whether the computer could have stopped it. That tells you which of your ideas were strong and which only worked because of a slip.
Rescue undo is fine sometimes
There are good reasons for rescue undo:
- You are a beginner and still learning the rules. Undo helps you explore without starting over every time.
- You are teaching a child. Undoing together and asking "what else could we play here?" is a gentle way to show alternatives.
- You tapped the wrong point by accident.
The problem is only when rescue undo becomes a habit that replaces thinking.
Using undo to study openings
Undo is also a way to explore the first few moves. Play an opening, see how the computer responds, then undo and try a different second or third move. After a dozen tries you will have a feel for which shapes give you lines in several directions and which get blocked quickly. This is more effective than memorising sequences, because you see the reasons.
Undo and the rule settings
Undo works the same under the Vietnamese blocked ends rule and freestyle. One useful exercise is to play the same position under both rules: reach a critical middle game, then switch rules in a new game and try to reach a similar position. You will see how a five closed at both ends changes the value of blocks and attacks.
Keeping track of what you learn
If you sign in on the account page, your games are saved and you can replay them move by move later. That is useful for review days, when you look back over a week of games and notice which mistakes repeat. Over time the list of repeated mistakes gets shorter, which is the clearest sign of progress.
A three-game challenge
Try this: play three games at your usual level without any undo at all, not even for accidents. Then play three more games using undo only after each game, for review. Compare how you feel about the positions in the second set. Most players find that the no-undo games make them more careful, and the review sessions make the lessons stick.
Undo and resigning
Undo is not the only way to deal with a bad position. Sometimes the honest move is to resign and start fresh, especially when the computer has a clear double threat and you have no fours to play. Resigning and then reviewing the game with a fresh board often teaches more than undoing the last few moves and hoping for a different outcome. There is no penalty for resigning against the computer, and there is also a leave button if you simply want to stop and change settings.
What strong players do
Players who improve quickly tend to treat every game against the computer as material for study. They play honestly, without take-backs, and then spend a few minutes afterwards on the one or two moments that decided the game. They rarely replay the whole game; they go straight to the turning point. Adopting this habit is more important than any single tactic, because it keeps your learning focused on your own real weaknesses.
One question to ask every time you undo
Whenever you press undo, ask yourself a single question before playing again: what did I not see? If you can name it, a diagonal, a split three, a landing point, the undo was worth it. If you cannot, step back further until you can. That one question turns every take-back into a small lesson.
Frequently asked questions
Is using undo against the computer cheating?
No. It is your practice, and undo is there to help. Just be aware that rescue undo teaches less than review undo.
Can I undo in online games?
No. Online games against real people have no take-backs.
How far back can I undo?
You can step back move by move. Each undo returns you to your previous turn.
What is the best way to review a lost game?
Find the move where the opponent's winning shape first became possible, and replay from there with a different choice.
Should beginners use undo freely?
In the first few games, yes. Once you know the rules, move toward using it mainly for review.
