How to play Binary Puzzle

Fill the grid with 0s and 1s: never three the same in a row, half of each in every line, and no two rows or columns alike. Also known as Takuzu, Binary Sudoku, 0h h1.

▶ Play Binary Puzzle ⊞ Open the solver

The rules

Every square holds a 0 or a 1 (here 6×6 to 12×12; the size is always even).
No more than two of the same number may sit next to each other in a row or column.
Each row and each column contains as many 0s as 1s.
No two rows are the same, and no two columns are the same.

Playing Binary Puzzle on Puzzle Solvers

Choose a grid size (6×6 to 12×12) and a difficulty, then press New Puzzle.
Tap a square to cycle it: empty, 0, 1. Right-click goes the other way. Or select a square and type 0 or 1.
The counts beside each row and under each column show its 0s and 1s; squares that break a rule glow red.
Hint fills a square and explains why. Switch the look to sun and moon or plain colours. Send to Slate puts the puzzle on a Slate whiteboard; Print gives a paper copy.

Open the Binary Puzzle game →

Using the Binary Puzzle solver

Choose the grid size and tap squares to copy in your puzzle (empty → 0 → 1), or press Sample.
Press Solve and step through: pairs, gaps, counts, line checks and the no-twins rule, each explained and highlighted.

Open the solver →

A worked example

A 6×6 row reads 1 1 _ 0 _ _. The pair of 1s forces a 0 in the third square: 1 1 0 0 _ _. Now the 0 0 pair forces a 1 in the fifth square: 1 1 0 0 1 _.

The row has three 1s already — all it is allowed — so the last square is 0: 1 1 0 0 1 0.

Strategies

Pairs. Two of the same side by side (0 0) must be closed off with the other number on both ends: 1 0 0 1.
Gaps. A square between two equal numbers (1 _ 1) must be the other number, or there would be three in a row.
Counting. Once a row has all of its 0s, the rest of it is 1s — and the other way round.
Line check. When a line is nearly full, list the ways it could still be finished. If every way puts the same number in a square, fill it in.
No twins. If a line could end up the same as a finished line, the squares that would make it identical must take the other number.

Common mistakes

Only checking rows — the three-in-a-row rule and the half-and-half rule apply to columns too.
Forgetting the no-twins rule late in the puzzle, when it is often the only way forward.

Where it comes from

Binary puzzles were popularised in Belgium and the Netherlands around 2009 and in Japan as Takuzu. They are easy to learn — only two symbols — yet a 12×12 grid can be a real challenge.

Frequently asked questions

Is this the same as Takuzu or Binairo?

Yes — they are names for the same kind of puzzle. Some versions use two colours instead of 0 and 1; the game lets you switch to colours or sun and moon symbols.

Do I need to know binary numbers?

No. The 0s and 1s are just two symbols; no arithmetic is needed. It is a great first logic puzzle for younger children.

Why is there a counter next to each row?

It shows how many 0s and 1s the row has so far, so you can spot when a row has all of one number.

Can the solver explain a puzzle from a book?

Yes. Copy it into the Binary Puzzle Solver and step through every pair, gap, count and line check.

Keep going

All guides: How to play every puzzle and game.