Rules & objective
Connect four discs horizontally, vertically or diagonally.
- You play coral and move first; the computer plays gold. Select a column to drop your disc into its lowest empty square.
- A full column cannot accept another disc. Wait for the computer’s move before selecting your next column.
- The first side to connect four wins. If the board fills without a winner, the round is a draw.
Key terms
- Threat
- A move that would complete a line of four on the next turn.
- Playable square
- The lowest empty square in a column, where the next disc can actually land.
- Fork
- A position creating two distinct winning threats that cannot both be blocked with one move.
Difficulty levels
| Level | What changes |
|---|---|
| Easy | A casual opponent that chooses random legal columns. |
| Medium | The computer takes immediate wins and blocks your next win. |
| Hard | The computer looks five plies ahead and weighs future threats. |
Changing difficulty starts a fresh round. Personal bests are tracked separately.
This version on puzzle free online
Easy chooses random legal columns. Medium takes immediate wins and blocks immediate losses. Hard looks ahead across five plies, meaning five individual turns, and evaluates future threats; it is not described as unbeatable.
Common questions
Can I place a disc in any empty square?
No. You choose the column; the disc falls to the bottom available square.
Does a diagonal line count?
Yes. Four consecutive discs on either diagonal direction win, just like a horizontal or vertical line.