Dots & Boxes rules and how to win

Dots & Boxes modes

• Play against the CPU (CPU対戦): four levels, Starter, Beginner, Intermediate and Advanced. You can choose to go first or second and the board size (3×3, 5×5 or 7×7)
• Two players on one device (ふたりで対戦): take turns on one screen
• Random Match (ランダムマッチ): find an opponent online (5×5 board)
• Room Match (ルーム対戦): play a friend using a room ID. The player who creates the room chooses the board size

Basic rules of Dots & Boxes

• Two players take turns drawing one vertical or horizontal line between two neighboring dots.
• Whoever draws the fourth side of a square takes that box. A single line can close two boxes at once.
• After taking a box, you draw another line. If you did not take a box, it is your opponent's turn.
• When all the lines have been drawn, the player with more boxes wins.

How to play on Asobi Lounge

• On a computer, move the mouse near where you want to draw and a faint line appears; click to draw it. With the keyboard, select the board, choose a line with the arrow keys and press Enter to draw it.
• On a phone, touch the board and the nearest line appears. Slide your finger to choose a line and lift it to draw.
• When you touch a line, the boxes you would hand to your opponent by drawing it are shown with yellow dotted lines. Boxes you can take right now are shown with a dotted outline.
• Against the CPU, Undo (待った) takes you back to your own move. Hint (ヒント) can be used up to 3 times per game and shows in gold the line the strongest CPU would choose.

Board sizes and number of lines

The bigger the board, the more lines there are, and the longer the opening, where players trade "safe lines," lasts. Here are the numbers for this site's three boards (with n boxes per side, there are (n + 1) squared dots and 2 × n × (n + 1) lines).

• 3×3: 16 dots, 24 lines, 9 boxes. Games are short, which makes it good for learning the rules.
• 5×5: 36 dots, 60 lines, 25 boxes. Random matches use this board.
• 7×7: 64 dots, 112 lines, 49 boxes. Several chains form, and the endgame takes longer to work out.

How the CPU levels differ

• Starter: usually takes a box when it can, but draws lines on a whim and often draws a third side.
• Beginner: takes every box it can and, while safe lines (lines that do not make a third side on any box) remain, never draws a third side. When it has to give boxes away, it chooses the line that gives away the fewest.
• Intermediate: counts chain lengths. Once safe lines run out, it hands over the cheapest chains first, and in long chains it deliberately gives back the last 2 boxes to keep control.
• Advanced: thinks the same way as Intermediate, but reads ahead from earlier on, while safe lines still remain, choosing lines so that the number of long chains works in its favor.

Example: give back the last 2 boxes to win the long chain

Late in the game, safe lines have run out, only a 3-box chain and a 6-box chain are left on the board, and it is your turn. You have to open one of them and hand it over, so you open the shorter 3-box chain.

1. If your opponent takes all 3 boxes, they must then draw another line, which opens the 6-box chain. In that case you take the 6 boxes: you 6, opponent 3.
2. So instead, your opponent takes just 1 box, then draws the end line rather than the line between the remaining 2 boxes, giving those 2 boxes back to you.
3. You take the 2 boxes, but after that the only lines left to draw open the 6-box chain.
4. Result: opponent 1 + 6 = 7 boxes, you 2. By giving back 2 boxes, your opponent won the long chain. CPUs at Intermediate and above count whether giving boxes back pays off when they choose a line.

Tips for winning

• While safe lines remain, the basic rule is not to draw the third side of a box.
• Once safe lines run out, hand over the short chains first. Give away a 2-box chain by drawing the line between its two boxes; your opponent then has to take both and cannot give them back.
• When you are handed a long chain, count before taking all of it whether giving back the last 2 boxes pays off. The longer the chains left afterward, the more giving them back is worth.
• Giving back boxes from a loop means handing 4 boxes to your opponent, so it costs more than with a chain.
• On the 5×5 board (36 dots), a known rule of thumb is that the first player wants an even number of long chains (3 boxes or more) and the second player wants an odd number (loops do not count). You adjust the number of chains through the lines you draw in the middle game.

Frequently asked questions

Does going first or second give an advantage?

It depends on the board size and how many long chains form in the endgame. Against the CPU you can choose to go first or second, so try both.

Can a game end in a draw?

The boards on this site (3×3, 5×5 and 7×7) have an odd number of boxes, 9, 25 and 49, so there are no draws.

What if one line closes two boxes?

Both boxes are yours, and you draw another line.

Is Dots & Boxes 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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