Connect 4 rules and how to win

Connect 4 modes

• Random match (ランダムマッチ): find an opponent online
• Room match (ルーム対戦): play a friend using a room ID
• Play against the CPU (CPU対戦): four levels, Novice, Beginner, Intermediate and Advanced. You can choose to go first (red) or second (yellow)
• Two players (ふたりで対戦): take turns on one screen

Basic rules of Connect 4

• Red (first) and yellow (second) take turns dropping discs into a board of 7 columns and 6 rows (42 squares).
• A disc stops on the lowest empty square of the column you choose. You cannot drop a disc into a full column.
• As soon as you line up four of your color in a row vertically, horizontally or diagonally, you win.
• If all 42 squares fill up without four in a row, the game is a draw.

How to play on Asobi Lounge

• On a computer, hover over a column to see the disc and where it will stop, then click to drop it.
• On a phone, press and hold, slide left or right to choose a column, and let go to drop the disc there.
• Against the CPU, Undo (待った) takes you back to your own move. Hint (ヒント), up to three times per game, shows the column the strongest CPU would choose.
• Start an online game by sharing a room ID or with a friend invite. When a game ends and both players choose a rematch, you can play another game right away.

Why the center column is strong

On a 7×6 board there are 69 possible lines of four: 24 horizontal, 21 vertical and 24 diagonal. The number of lines that pass through a square varies a lot by position. On the bottom row, an edge square is part of 3 lines, while the center square is part of 7. The center squares of the third and fourth rows from the bottom are part of 13 lines, the most on the board.

The more discs you put in the center column, the more possible lines you have and the fewer your opponent has. That is why a first move in the center is considered standard for the first player.

How the CPU levels differ

• Novice: drops almost at random, with a slight preference for the center. It misses chances to make four and forgets to block.
• Beginner: never misses a winning move or a move that blocks your four. Otherwise it reads 3 moves ahead, but sometimes falls into traps.
• Intermediate: reads 8 moves ahead and compares the number of shapes that need only one more disc.
• Advanced: reads deeper for about 1 second per move and reads the game perfectly to the end from the middle game on.

Example: the square below a "one more" square

Suppose red has three in a row horizontally, and the square to their right is empty. But the square below it is still empty too.

1. If yellow drops a disc into the square directly below, red can drop into the square above it, the fourth square, and red wins.
2. If red drops into the square below, yellow can drop on top of it and block the fourth square.
3. So the square directly below is a place where whoever plays first loses out. Neither player plays in that column, and as the other columns fill up, someone is forced to. In the endgame, reading this order of moves is what decides the game.

Tips for winning

• The center column is part of many vertical, horizontal and diagonal lines, so taking the center early gives you an advantage.
• If your opponent has three in a row, you lose unless you block it on your next move. Always keep track of your opponent's lines.
• If you create two "one more" spots at once, your opponent can block only one. Two threats stacked one above the other are especially strong.
• As a rule of thumb, the threats that pay off in the endgame are on the 1st, 3rd and 5th rows from the bottom for the first player, and on the 2nd, 4th and 6th rows for the second player.
• The Advanced CPU reads to the end from the middle game, so to beat it you need to build a good position in the opening. Try it once you are winning more games than you lose against Intermediate.

Frequently asked questions

Which is better, going first or second?

On a board of this size (7 columns by 6 rows), it was confirmed by computer in 1988 that the first player can always win by starting in the center and playing correctly to the end. But playing perfectly all the way is very hard, so in games between people, both sides have a real chance to win.

Can a game be drawn?

Yes. If all 42 squares fill up without four in a row, it is a draw.

Is it the same as four in a row played on paper?

Connect 4 on this site is the four-in-a-row game where you drop discs into an upright board. Unlike versions where you can play on any square, you can only play on the lowest empty square of each column.

Is Connect 4 free to play?

Yes, it costs nothing. Games against the CPU and solo modes work right away without signing in. Online play (random matches and private rooms) and saving stats or leaderboard scores require signing in with a Google account. To play with a friend, your friend also needs to create an account and register as your friend.

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