The Story
Where it came from, and why it turned out this way.
DesignHoward Wexler and Ned Strongin · 1974 · published by Milton Bradley
A toy design, not an abstract game design
Connect Four was released by Milton Bradley in 1974, designed by Howard Wexler and Ned Strongin. It was conceived as a toy rather than a board game: an upright plastic frame, discs dropped in from the top, and a slide at the bottom that dumps them all out at once. Gravity is not merely a rule here — it is the product's physical selling point. Many abstract games work on paper first and then look for a form; Connect Four went the other way around.
Gravity is the actual mechanism
Remove gravity and let discs land on any square freely, and the game becomes immediately unremarkable. What creates the depth is that you choose a column and not a row: whether a threat ever pays off depends on who ends up filling the square below it. Defense therefore becomes a trap of its own — you drop a disc to block a threat that is not yet reachable, and in doing so hand your opponent the winning square.
In 1988 two people solved it at once
The 7×6 game was solved independently twice in 1988: James D. Allen and Victor Allis — the same Allis who would crack Gomoku five years later — reached the same conclusion at almost the same time. The first player wins by opening in the exact center column, draws by opening in either adjacent column, and loses by opening in the outermost columns. The result of the game, in other words, is settled on move one.
Parity: the technique the solution left behind
Being solved did not drain the game; it left behind an elegant piece of human technique — classifying completion squares by row parity. As a column fills, the rows each player occupies alternate predictably, so the first player's winning squares belong on odd rows and the second player's on even rows. What strong players do in the endgame is force their opponent to fill the row they need. That parity theory was reverse-engineered from the full solution.
- The knowledge-based search Allis used on Connect Four is the direct ancestor of the threat-space search he later used to solve Gomoku, only five years apart.
- Squares in columns 1 and 7 belong to the fewest possible lines and column 4 to the most — the value of the center column can be counted literally, as the number of fours each square participates in.
- Connect Four is a registered trademark, which is why electronic implementations frequently use names like Four in a Row instead.
Complete Rules
Start with what a turn allows and how the game is won.
- Board
- 7 columns × 6 rows
- First move
- Red
- Winning conditionthe first player to get four consecutive disks of their color in a row, a column, or either diagonal wins immediately. If all 42 squares are filled with no such line, the game is a draw.
- How a turn workseach turn you choose a column, and gravity drops your disk into the lowest empty square in it. Clicking anywhere in a column selects that column — you cannot specify a row. Disks are permanent once placed and never move or come back.
- A column already holding six disks cannot be chosen, and the interface marks it unavailable. As long as any column has space you must play; passing is not allowed.
- Victory is checked after every drop, and the player who completes four first wins outright — the opponent never gets a compensating move.
- A single move that completes two or more lines of four still counts as one win, and the winning line is highlighted on the board so you can see exactly where the game was decided.
- By default you play Red and move first, but the settings let you take Yellow and move second. Switching starts a new game immediately.
Your First Game
Use this order of thought to get through a complete game quickly.
- Play your first disk in the middle column, column 4. Connect Four on a 7×6 board is completely solved: the first player wins only by opening in the exact center, opening in the adjacent columns 3 or 5 is a draw, and opening in the outermost columns 1 or 7 loses. The theoretical result is settled by that one move.
- The center column is valuable because of how many lines it participates in: every square in column 4 can belong to lines in all four directions, while edge squares have far fewer usable directions. Prioritize the middle three columns for the entire game.
- Before every drop, ask: which square did I just make reachable for my opponent, and can they win by dropping directly on top of my disk? This is the single biggest source of losses in Connect Four — not failing to see a threat, but personally handing over the ladder to it.
- What matters is not the three disks already lined up, but the row of the empty square that would complete them and whether the squares beneath it are filled. A three-in-a-row whose completion square is floating high in the air is no threat at all; one sitting right at the current fill level is an emergency.
- Creating two winning squares in two different columns wins, because your opponent can only block one per turn. The easiest version to build shares one disk between a horizontal three and a diagonal three, with the two completion points in different columns.
- Count your opponent's threats the same way: do they have a three forming, and in which column and row does it complete? Block the completion squares that are reachable on their very next move first; the floating ones can wait.
Practical Strategy
Move from knowing the rules to playing with a plan.
- Classify completion squares by row parity — this is the central technique of the game. Counting from the bottom, rows 1, 3, and 5 are odd and rows 2, 4, and 6 are even. As a column fills square by square, the rows each player occupies alternate predictably, so Red (moving first) wants their winning squares on odd rows and Yellow (moving second) wants theirs on even rows.
- Holding an odd-row threat as the first player often forces your opponent to fill that square for you in the endgame: once the other columns are full, they eventually have no choice but to play into that column. The second player counters with even-row threats while avoiding any move that sets up an opponent's odd-row square.
- Do not raise a critical column without a reason. Every additional disk in a column hands the square above it to your opponent, and sometimes the best move is a disk in an irrelevant column — giving the turn back and forcing your opponent to touch the critical column first.
- Two completion squares stacked vertically in the same column are especially strong: your opponent blocks the lower one, and you take the one directly above it. This stacked threat is the most common winning shape in the endgame.
- Connect Four has a far smaller branching factor than most games — at most seven options per turn — so in the endgame you can calculate forcing lines column by column instead of relying on intuition. Start exact calculation once about a dozen squares remain.
- When behind, complicate: pile disks in the center and leave several half-formed diagonals so your opponent has to check more directions every move. When ahead, do the opposite — block every one of their completion squares early and simplify the game into plain filling.
Winning and Special Rules
Details that are easy to miss but can change the result.
- Victory is checked after each drop, and the player who reaches four first wins outright with no compensating move for the opponent. You never need to account for "one more move" when calculating a win.
- A completely filled board with no line of four is a draw. Draws are not rare in practice, especially when both players open in adjacent columns.
- You play Red and move first by default, but can switch to Yellow and move second. Correct strategy differs completely between the two — odd rows versus even rows — so switching sides means switching your whole approach.
- The higher AI levels use iterative-deepening alpha-beta search that prioritizes immediate wins and forced defenses, so it almost never misses a one-move win and will not overlook any double threat you leave available.
Common Mistakes
The traps new players fall into most often.
- Blocking only the visible horizontal three and missing a diagonal that becomes live once the supporting square below it is filled. Diagonals are the least visually obvious lines and the most common winning direction in the game.
- Dropping a disk to stop a threat that is not yet reachable, and thereby raising the column so your opponent's winning square lands right in their hands. Defending a floating threat is often worse than not defending it at all.
- Avoiding the center for too long and stacking disks in the edge columns, only to find the central lines are already occupied. Squares in columns 1 and 7 participate in the fewest lines, so early moves there are largely wasted.
- Counting your own threes without counting the row of the completion square. A completion square on row 5 and one on row 2 have completely different urgency.
- Rushing to block your opponent's three when both ends of that line are already sealed by your own disks, throwing away a turn for nothing.