Connect Four

How to Play Connect Four

1. 1Pick vs Computer (Easy/Medium/Hard) or 2 Players.
2. 2Click a column to drop your disc — it falls to the lowest empty slot.
3. 3Line up four of your colour in a row — across, up, or diagonally.
4. 4Block your opponent's three-in-a-row, and use Undo to explore ideas.

The Rules, in Short

Connect Four is played on a vertical grid seven columns wide and six rows tall — forty-two slots in all. Two players each own a colour (here, red and yellow) and take turns dropping one disc per turn into any column that is not yet full. Gravity does the rest: the disc settles on top of whatever is already in that column. The first player to form an unbroken line of four of their own discs — horizontally, vertically, or along either diagonal — wins immediately. If every slot fills without a line of four, the game is a draw.

It sounds simple, and the rules truly are, but underneath sits a surprising amount of tactics. Every disc you drop changes which squares your opponent can safely use next, so a game of Connect Four is really a running battle over space and threats.

Playing Against the Computer

The computer opponent comes in three strengths. Easy plays sensibly and will always take an obvious win or block an obvious threat, but it does not plan far ahead — a good level for children and newcomers. Medium looks a few moves into the future and punishes loose play. Hard runs a deeper minimax search with alpha-beta pruning, weighs the whole board, and favours the centre, so it plays a strong, consistent game. Every level shares two guarantees: it will take a winning move the instant one appears, and it will block yours whenever you threaten four — so cheap wins are off the table and you have to genuinely out-think it.

Winning Strategy

A handful of ideas will lift your game quickly. Take the centre — the middle column touches the most possible fours, so a disc there is worth more than one on the edge. Create two threats at once. The winning tactic in Connect Four is the “double threat”: a move that makes two separate three-in-a-rows so your opponent can only block one. Watch the odd and even rows — advanced players count which rows their threats sit on, because the player moving first tends to benefit from threats on odd rows and the second player from even ones. And always scan for the opponent's three-in-a-row before you play your own plan; one missed block ends the game.

The History of Connect Four

Connect Four in its familiar plastic form was introduced by Milton Bradley in 1974, co-created by the inventor Howard Wexler, and quickly became a fixture of family game nights. But the underlying idea of dropping pieces to make a line is much older, and the game is sometimes linked to a piece of folklore: a vertical four-in-a-row game supposedly known as “the Captain's Mistress,” said to have been a favourite pastime of Captain James Cook on his long voyages — a charming story, if not firmly documented.

What is certain is that the modern game's brilliant piece of design is gravity. Because discs fall to the lowest empty slot, you cannot place a piece just anywhere — your choices are constrained to the top of each column, and every move changes where future pieces can land. That single mechanic transforms a simple line-making game into one with genuine spatial depth, which is why it has stayed popular for half a century.

Connect Four Is a Solved Game

Here is a fact that surprises most players: Connect Four has been completely solved by computers. In 1988, two researchers — James Dow Allen and, independently, Victor Allis — proved that on the standard seven-by-six board, the first player can always force a win with perfect play, provided they start in the centre column. If the first player opens anywhere else, the outcome can be a draw or even a loss with best play from both sides.

This makes the opening move genuinely important: the centre column is not just a good idea, it is the winning idea, because a disc there participates in the greatest number of possible four-in-a-rows — horizontal, vertical, and both diagonals. Of course, “solved” only matters between perfect players, and no human plays perfectly. Even a strong computer like the Hard level here is not a flawless solver, so games remain competitive and winnable. But knowing the theoretical truth — take the centre — gives you a concrete edge from the very first move.

Advanced Tactics: Threats, Zugzwang, and Odd/Even

Beyond controlling the centre, the decisive weapon in Connect Four is the double threat: engineering a position where a single move creates two separate three-in-a-rows at once. Your opponent can only block one, so the other completes your four. Almost every won game at a decent level comes down to setting up a double threat your opponent cannot escape. The counter-skill is vigilance — always scanning for the opponent's open threes and blocking them before pursuing your own plan.

The deepest layer of strategy involves odd and even threats and the concept of zugzwang (being forced to make a move that damages your own position). Because the board has six rows and players alternate, expert play tracks whether a threat sits on an odd-numbered row (counting from the bottom) or an even one. As a rough guide, the first player tends to benefit from threats on odd rows and the second player from even rows, because of who is forced to fill the squares beneath them as the board fills up. A player who can create an unanswerable odd threat and then simply wait, letting the board fill until the opponent is forced to hand them the winning square, is using this idea. It takes practice to see, but it is the difference between a good player and a great one.

How to Improve Your Game

The fastest way to get better is deliberate practice against the Hard computer, using the unlimited undo as a learning tool: play a move, watch how the computer responds, then take it back and try a different idea to see which lines lead where. This experimentation builds your intuition for threats and traps far quicker than simply playing game after game.

Focus your attention on three habits: open in the centre every time, get into the habit of scanning the whole board for both players' threes before each move, and actively look for moves that create two threats rather than one. Master those, and you will beat most human opponents comfortably and give the computer a real fight. The rules take seconds to learn, but as the solved-game theory shows, the strategic depth beneath them rewards a lifetime of study.