Connect 4

How to play

You and the computer take turns dropping a disc into a column. The first to line up four discs of the same color horizontally, vertically or diagonally wins.

Tip

Control the center: it creates more threats. And watch the computer's moves, as it blocks your lines and tries to win!

The game is solved, and whoever starts wins

Connect 4 was solved mathematically in 1988, by James Allen and Victor Allis independently: on a standard seven-by-six grid, whoever moves first always wins, provided they play perfectly. And there is only one winning first move: the centre column.

Any other opening hands the opponent at least a draw. It is why, between two players who know what they are doing, the outcome is decided before the start, and why in tournaments the opening move alternates. The interesting game is the one between imperfect human players, which is where all the fun lives.

Why the centre is worth more than anything

A square in the middle of the grid takes part in far more possible fours than a square at the edge: horizontals, verticals and both diagonals. In the centre column a disc belongs to seven potential lines, in the outer one to three. It is a structural advantage, not a matter of style.

Hence the practical rule that always holds: contest the centre even when there is no immediate threat. Anyone spending the game responding at the edges arrives at the end with discs that take part in nothing, and that is the typical beginner's defeat.

The odd and even row rule

This is the concept strong players use and that you do not discover on your own. Since the discs fall, every column fills from the bottom: squares are occupied in order, and that makes it predictable who will reach which row. In the standard version, the first player tends to complete threats on the odd rows counting from the bottom, the second on the even ones.

The practical consequence is that a threat built on the wrong row never materialises: the opponent gets there first by construction. So the first player looks for lines that close on the first, third or fifth row, and the second player for the opposite.

The double threat, that is how you actually win

A single threat is not enough: the opponent blocks it and the game continues. You win by creating two threats at once, so that blocking one leaves the other open. The commonest shape is called the seven trap: three discs placed so that two different columns complete the line.

The mirror-image error is the gift move: placing a disc in a column where, immediately above it, the opponent completes a line. It is the most frequent way to lose, and it happens when you look only at your own threat: before playing in a column it is always worth asking what happens to the square directly above.

Nearby tools

For another logic game there is Minesweeper, and for words Guess the word and General knowledge quiz. For an evening with friends Scoreboard and Tournament bracket.