Connect Four

Connect Four is the classic two-column drop-and-connect strategy game, played against an AI opponent on an HTML5 canvas. Drop a disc into one of seven columns; it falls to the lowest free row; the first player to line up four of their discs — horizontally, vertically or diagonally — wins.

The opponent is minimax with alpha-beta pruning over the 7×6 board. Its evaluation function is hard-coded and weighs centre-column control, immediate threats and blocking moves, so it plays a strong game without opening deliberately. It will not always pick the theoretically best move.

How to Play

1. Click a column (or use the number keys) to drop your disc.
2. Watch the AI think — it replies in under a second at normal depth.
3. Connect four to win. Fill the board with no winner and it is a draw.
4. Use Undo to take back a move, or New game to restart.

Controls

• Click a column — drop a disc there
• 1 – 7 — drop into the matching column from the keyboard
• Undo — take back the last move
• New game — restart
• Reset — clear the board and the win indicator

Tips

• The centre column is worth more than any other because every line that runs through it also runs through more winning combinations. If the AI gives you a free turn there, take it.
• Play threats, not potential. A disc that completes four wins; a disc that completes three and has an open end on both sides forces the AI to answer and loses you nothing.
• Set up two simultaneous threats and the AI cannot block both. Double threats beat search depth.
• Undo is unlimited. If you are analysing rather than playing, use it freely.

Save Data

Nothing is persisted. A page reload starts a new game.

Open Source & License

Connect Four (c4) was created by Kenrick and is licensed under the MIT License.

• Original game source: https://github.com/kenrick95/c4
• Original live build: https://kenrick95.github.io/c4/

This integration self-hosts that build so it runs entirely in your browser. It was compiled from the upstream monorepo with the upstream toolchain; the only build flag changed was making Vite emit a relative asset base so the game works from its embedded path. The optional online-play server component is not included, since this build is single-player against the AI.