How to win at Four in a Row
Strategy · · 4 min read
Four in a Row takes a minute to learn: drop a disc into one of seven columns, and the first to line up four, across, up or diagonally, wins. Most games between beginners are decided by one missed threat. Games between stronger players are decided much earlier, by where the discs went in the first moves and on which rows the threats ended up.
This guide goes from the habits that stop you losing to the idea that wins long endgames. Each one can be tried straight away against a bot.
Start in the middle column
Not every cell is worth the same. The board holds 69 possible lines of four, and a cell counts for more the more of them it belongs to. The bottom cell of the middle column is part of 7 lines; a bottom corner is part of only 3. Higher up the difference grows: the two middle cells of the middle column belong to 13 lines each, more than any other cell.
So the first disc goes in the middle, and the next few stay close to it. A disc on the edge can only ever be the end of a line. A disc in the middle can be the start, the end or the inside of one, in every direction.
Win first, block second
Before every move, ask two questions in this order. Can I make four right now? Can my opponent make four on their next move? If the first answer is yes, play it, even if your opponent also has a threat. If only the second is yes, block it, because nothing else matters.
It sounds obvious, and it is still how most games against beginners are lost: a three in a row with an open fourth cell, waiting in plain sight while the player builds something elsewhere.
Look at the cell above
Gravity changes what a move does. Every disc you drop makes the cell above it playable. If your opponent has three in a line whose fourth cell is exactly there, your disc has just handed them the win.
So before you drop, check the cell your disc will open, not only the one it fills. The same trick works for you: a threat whose cell is not yet playable can wait, and the column under it becomes a column your opponent does not dare to touch.
Build two threats at once
One threat can be blocked. Two cannot, because your opponent only drops one disc per turn. Most wins come from such a double threat, and there are a few common shapes:
- An open three on the bottom row: three discs side by side with both neighbouring cells empty. Your opponent blocks one end and you play the other.
- Two threats on top of each other: two of your lines need cells that sit directly one above the other in the same column. When the lower one becomes playable, your opponent has to block it, and that opens the upper one for you.
- A three across and a three diagonally that share no cell: one drop can finish either, so your opponent can only stop one.
Odd and even rows: the endgame secret
Count the rows from the bottom, 1 to 6. In long games the board fills up, threats get stuck because the cells under them are empty, and in the end the players have to fill those columns. With all the other columns full, the discs go into what is left in turn from the bottom up, and the order works out so that the first player ends up filling the odd rows and the second player the even ones.
That is why, as Victor Allis set out in his analysis of the game, the first player wants a threat on an odd row and the second player can win with one on an even row. A threat on the wrong row usually gets blocked when the column fills; one on the right row is waiting for its owner. It is a simplification of Allis’s rules, but it is the idea behind most wins the Hard bot finds late in a game.
Why the first player wins, and how to practise
Four in a Row is solved. In 1988 James D. Allen and Victor Allis showed, independently of each other, that on the standard 7×6 board the first player wins with perfect play by starting in the middle column. Start in one of the two columns next to it, and the second player can force a draw; start further out, and the second player wins. Nobody plays perfectly at the board, so real games stay open, but it confirms the first lesson: the middle comes first.
To practise, play Four in a Row without an account against the bot. Easy shows you what happens when threats are left open, Medium blocks every four, and Hard looks about ten moves ahead. The Hint button names the kind of move it suggests, and after a loss the game shows the key moment. When you are ready for people, Four in a Row online is rated, with the first player drawn at random.