Four-in-a-Row — Drop Pieces to Connect Four
Drop pieces into a 7-column grid. Connect four of your colour in a row, column or diagonal to win.
How to play
- Click any column to drop your red disc — it falls to the lowest empty row.
- Connect exactly four of your red discs in a line (horizontal, vertical, or diagonal) to win.
- The AI plays yellow and uses a minimax look-ahead to try to beat you.
- Block the AI's threats while building your own lines.
- Click 'New Game' to reset the board.
Drop red discs into a 6×7 grid. Connect four of your discs in a row (horizontal, vertical, or diagonal) before the AI does. Uses a minimax AI with depth-3 look-ahead.
How it works
Four-in-a-Row (also widely known as Connect Four) is a two-player strategy game played on a vertical 7-column, 6-row grid. Players take turns dropping a coloured disc into any column; the disc falls to the lowest empty row in that column. The first player to connect four of their discs in a horizontal, vertical, or diagonal line wins.
Because discs fall under gravity rather than being placed freely, the game has a strong vertical and diagonal dimension. Building threats in multiple directions simultaneously — so your opponent cannot block everything in one move — is the core strategic skill. Control of the centre column is particularly valuable because it participates in the most potential four-in-a-row lines.
The widget's AI drops discs using a heuristic evaluation, giving casual players a meaningful opponent. It will block obvious threats and create its own, so you need to think at least two moves ahead to beat it consistently.
Four-in-a-Row is a perfect short puzzle for practising strategic thinking, threat counting, and the concept of forcing moves — ideas that transfer to many other strategy games.
Worked example
Create a double-threat the AI cannot block
- Drop your first disc into the centre column (column 4).
- On your next turns build a diagonal threat rising from the bottom-left while also placing discs horizontally across row 2.
- After four or five moves you should have three in a row diagonally AND three in a row horizontally, each needing one more disc in different columns.
- The AI can only block one; drop into whichever column it leaves open.
You connect four and win because the AI cannot block two simultaneous winning threats.
Common mistakes to avoid
- Playing only in response to the AI's threats and never building your own offensive lines — purely reactive play rarely wins.
- Ignoring diagonal threats: horizontal wins are most visible, but diagonals are harder to spot and the AI often exploits them.
- Filling a column too early: dropping into a column raises the floor for both players, which can inadvertently set up a winning spot for the AI.
Key terms
- Threat
- A sequence of three connected discs with an open space that would complete a four-in-a-row; the opponent must block it or lose.
- Double threat (fork)
- A position where you have two separate threats; since the opponent can block only one per turn, the other wins.
- Odd/even threat
- An advanced concept where the height (odd or even row) at which a threat can be completed determines which player wins when columns fill up.
Frequently asked questions
- How does the AI work?
- The AI uses a minimax algorithm with alpha-beta pruning at depth 3, scoring positions based on windows of 4 cells.
- Who goes first?
- You (red) always go first. Click any column to drop a disc.