How to play Sun & Moon
Fill the grid with suns and moons: the same number of each in every row and column, never three alike in a row, and every = or × sign obeyed. Also known as Binary with signs, Takuzu with signs, Equal–Opposite puzzle.
The rules
- Every square holds a sun or a moon.
- Each row and each column has as many suns as moons.
- No more than two of the same symbol may sit next to each other in a row or column.
- Squares joined by = hold the same symbol; squares joined by × hold different symbols.
- Optional classic rule: no two rows, and no two columns, are identical.
Playing Sun & Moon on Puzzle Solvers
- Choose the rules, how many clues are signs, a size and a difficulty, then press New Puzzle.
- Tap a square to cycle sun → moon → empty, or pick the Sun or Moon tool (S / M) and drag across squares.
- Broken rules light up red: three in a row, too many of one kind, or a sign that doesn’t fit.
- Hint explains the next square — signs, pairs, sandwiches, full lines and more.
Using the Sun & Moon solver
- Choose the size and rules, then enter the given suns, moons and signs (or press Sample).
- Press Solve and step through: signs, pairs, sandwiches, full lines, and the ways a line can still be finished.
A worked example
In a 6×6 row, R1C1 and R1C2 are both suns. A third sun can’t follow, so R1C3 is a moon.
There is a × between R1C3 and R2C3, so R2C3 is the opposite — a sun.
Strategies
- Follow the signs. As soon as one side of a sign is known, the other side is too. Chains of signs can carry a symbol across the grid.
- Pairs. Two suns side by side must have moons at both ends.
- Sandwiches. A gap between two suns must be a moon.
- Full lines. Once a row has half its squares as suns, the rest are moons.
- Signs in a line. An × in a line uses one sun and one moon, so it counts towards both totals — useful when counting what is left.
Common mistakes
- Reading × as ‘wrong’ — it means the two squares are different.
- Counting only the symbols and forgetting the signs inside a line.
- Making three in a row across a sign.
Where it comes from
Binary puzzles (Takuzu, Binairo) date from the 2000s. Adding = and × signs between squares was popularised by daily puzzle apps in the 2020s.
Frequently asked questions
Is this the same as the daily sun-and-moon puzzles?
It follows the same rules as the popular daily versions: suns and moons, balanced lines, no three in a row, and = / × signs.
Can I play with 0 and 1?
Yes — turn on ‘Show 0 and 1 instead of ☀ and ☾’ under New Puzzle.
Is there always one answer?
Yes — every puzzle here is checked to have exactly one solution.
How do I solve one I found elsewhere?
Open the Sun & Moon Solver, enter the symbols and signs, and press Solve.
Keep going
- Play Sun & Moona fresh puzzle every time
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