What is Takuzu (a.k.a. Binairo)?

Takuzu is a binary logic puzzle: you fill a square grid with two symbols so that every row and column stays balanced and no three of the same symbol ever sit in a line. It goes by many names — and Solsticio plays it with suns and moons.

One puzzle, many names

If you've met this puzzle before, you may know it under a different label. They're all the same idea with cosmetic differences:

• TakuzuCommon name in French puzzle magazines and apps.
• BinairoThe name popularised in Belgium and the Netherlands (from “binary”).
• Binary puzzleThe plain descriptive name used in many puzzle books.
• UnrulyThe name used by Simon Tatham's well-known puzzle collection.
• TangoA recent sun-and-moon version that brought the puzzle to a huge new audience.

Solsticio is a sun & moon puzzle in this family: instead of 0s and 1s, you place ☀ suns and ☾ moons — the same logic, a warmer look.

Where it comes from

The puzzle is a modern descendant of classic binary and Latin-square logic. It spread through European newspapers and puzzle apps in the 2000s and 2010s, usually as “Binairo” or “Binary puzzle”, and picked up fresh popularity when a sun-and-moon edition reached mainstream players. The maths underneath is older still: balanced binary grids with an adjacency limit are a neat, self-contained corner of combinatorial logic.

The rules, in three lines

• No three in a rowNever three of the same symbol in a line, horizontally or vertically.
• BalanceEach row and each column holds the same count of both symbols.
• UniquenessA proper puzzle has exactly one solution, reachable by logic alone.

Classic Binairo stops there. Some variants (including Solsticio's later worlds) add connectors — an = means two cells match and an × means they differ — for extra deduction. Want the full walkthrough? See how to play and how to solve.

A solved 4×4 board: each line has two suns and two moons, and never three alike in a row.

Takuzu vs Sudoku

Both are pure-logic, no-guessing grid puzzles, but they feel different:

• SymbolsSudoku uses nine digits; Takuzu uses just two — so the reasoning is about pattern and balance, not arithmetic.
• RulesSudoku forbids repeats in rows, columns and boxes; Takuzu forbids three-in-a-row and enforces an equal split.
• RampTakuzu is quicker to learn and reads at a glance, which makes it a great daily puzzle.

Is it always fair?

A well-made Takuzu never needs guessing: every move follows from the rules and the symbols already on the board. Solsticio verifies each puzzle has exactly one solution and grades it by the hardest technique required, so difficulty rises smoothly and you're never stuck on a coin-flip. If you can't find a move, there's always one hiding — usually a pair or an almost-full line.

Play today's puzzle Learn the techniques

Prefer your phone? The free Android app has hundreds of levels and a new daily board.