What should you check before every move?
- Can you win now? Complete your own line of three. An immediate win ends the round, so there is no need to defend a threat the opponent will never get to play.
- Can the other side win next? If you have no immediate win, stop their line of two. A promising plan several moves away does not help if you lose on the next turn.
- Are there forks? Look for a move that creates two immediate winning threats. Check both your own opportunities and the opponent’s.
This is a useful thinking order. It is not a complete opening lookup table: when several forks or threats interact, look at the replies rather than blindly following a slogan.
Example 1: block the win in front of you
O is in the centre and X has the first two squares of the top row. O has no immediate win. The top-right square is therefore urgent: playing anywhere else lets X complete the row.
The numbered squares below are empty. They are labels for the diagram, not move values or points. Highlighted squares show the recommended move.
| X | X | 3 |
| 4 | O | 6 |
| 7 | 8 | 9 |
This is the only move that avoids a forced loss. With correct play from both sides afterwards, the position is a draw.
Example 2: defend against opposite corners
X has two opposite corners and O has the centre. It is O’s turn. Taking another corner looks attractive, but it gives X a fork. Choose an edge instead: the top-middle, middle-left, middle-right or bottom-middle square.
All four edges can hold a draw in this exact position with correct follow-up play. The advice is position-specific: if a win or immediate block exists on another board, deal with it first.
| X | 2 | 3 |
| 4 | O | 6 |
| 7 | 8 | X |
Every highlighted edge can hold a draw. Choosing either empty corner lets X force a win.
Example 3: make two threats with one move
This is what can happen if O chooses the top-right corner in the previous example. X can now play the bottom-left square. That move blocks O’s diagonal and creates two threats at once.
X can win next in the middle-left square to complete the left column, or in the bottom-middle square to complete the bottom row. O can occupy only one of those squares and has no immediate winning move of its own.
That last check matters. Two threats are useful only if the opponent cannot end the game before you use them.
| X | 2 | O |
| 4 | O | 6 |
| 7 | 8 | X |
X then threatens square 4 in the left column and square 8 in the bottom row. O cannot block both and has no immediate winning move.
Should you start in a corner or the centre?
Either a corner or the centre can support a draw with perfect follow-up play. A corner can invite mistakes against a beginner, while the centre touches four possible winning lines. Neither square is a guaranteed win on its own.
When the first player opens in a corner, taking the centre is a reliable defensive reply. If the first player opens in the centre, a corner is a reliable reply. Then return to the win, block and fork checks rather than repeating a memorized pattern after the position changes.
How should you practise?
Play a few rounds on Medium and say why you chose each square: “this wins”, “this stops a line” or “this prevents a fork”. Review the earliest missed threat after a loss, not just the final move.
Next try Hard. In our implementation, Hard searches the remaining game and never gives away a forced loss from the usual starting board. A consistent draw is the target; a claim that you can always beat a perfect opponent is misleading.
Open Tic-Tac-Toe to practise, or revisit the rules and rematch setup. These teaching boards are static examples; the game starts its own round.
Questions
- Can you always win Tic-Tac-Toe? No. Correct play from both players produces a draw. Winning requires the other side to make a mistake that you can exploit.
- What is a fork? A move that creates at least two different squares where you could win on your following move. Check that your opponent cannot win immediately first.
- Can the second player avoid losing? Yes. The second player can hold a draw from the empty starting board with correct play. Going first is not an automatic win.
