How to play
The grid stands upright, seven columns wide and six rows tall, 42 holes in all. Red always goes first. Against the computer you are red and it plays yellow.
A turn is a single action: tap a column. Your disc drops to the lowest empty hole in that column, and you can’t choose a higher spot. Once a column is full, it stops taking discs.
Four of your discs touching in one line win the game. The line can run across, straight up, or along either diagonal, and it can sit anywhere on the grid. When you win, the winning four light up. If all 42 holes fill and nobody has four, the game is a draw.
That’s the whole rulebook. The depth comes from gravity: you can only play where a disc can actually land, so a threat high up the grid sits there waiting until the column grows to meet it.
The buttons
New game starts over. Undo takes back your last disc together with the computer’s reply; in friend mode it takes back one disc. Hint lights up the column a medium-strength search would pick for the player to move.
Under Opponent you can switch between Computer and Friend. Friend mode is for two people sharing one screen, red against yellow, and the status line names whose turn it is. Against the computer, choose Easy, Medium or Hard. Easy looks only at its own next disc and plays loosely, so it often misses a threat. Medium reads three discs ahead (its, yours, its). Hard searches up to six discs deep, three for each side, and rarely falls for a simple trap. Your game in progress, opponent and level are remembered.
Strategy
Start in the middle. The centre column belongs to more possible lines of four than any other column, because a line through the centre can extend either way. The computer weighs centre discs higher too. Columns at the edges are the weakest: a disc in the far left column can only help lines that run to the right.
Never give a free spot. Before every move, look at the hole directly above where your disc will land. If your opponent has three in a row waiting on that hole, your disc just lifted them into it. Many lost games come from this single mistake.
Make two threats with one disc. A move that opens two separate winning holes can’t be answered, since your opponent blocks one and you take the other. The most common shape is a diagonal and a horizontal line sharing one disc.
Stack your threats. Two of your winning holes directly on top of each other, in the same column, are a near-certain win. The opponent must block the lower one, and that block lifts you into the upper one.
Know your rows. Number the rows 1 to 6 from the bottom. As the grid fills, the first player tends to benefit from threats on odd rows and the second player from threats on even rows. That’s because of turn order when columns fill up near the end. If you play red, an unanswerable threat on row 3 or row 5 often decides the game long before it is cashed in.
Play the long game against Hard. The computer at its top level won’t leave easy threats open, so wins come from structure: a stack of threats on your good rows, and patience while the board fills.
Mathematicians worked out in 1988 that red, moving first, can force a win on this 7 × 6 grid by starting in the centre column. Nobody plays perfectly, though, and yellow wins plenty of real games.
For a version on a bigger open board with no gravity, try Five in a Row. For a game where discs flip colours instead of falling, try Reversi.
If you enjoy Four in a Row, try Fox and Geese or Go 9×9 next.
