Sun & Moon Solver

Sun & Moon Solver — Step by Step

Click a square and press S for sun or M for moon. Click the line between two squares to add =, again for ×, again to remove. Then press Solve. Or play a generated puzzle and send it here with one click.

Sun & Moon Solver: rules, how to use it, tips

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.

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.

Using the 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.

Tips

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.

The full guide, with a worked example and common mistakes: How to play Sun & Moon.

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.