Duo

1. Fill every cell with a sun or a moon.
2. Each row and each column holds as many suns as moons.
3. No more than two equal symbols may sit next to each other in a row or column.
4. An = sign between two cells means they match; an × sign means they differ.
5. Locked symbols are given. Every puzzle has exactly one solution.

1. Balance the grid. Every row and column needs as many suns as moons, and never three equal symbols in a line.
2. Read the signs. An = joins two equal neighbours, an × two different ones. Tap a cell to cycle sun, moon and empty.

• Tap a cell to cycle it: sun, moon, empty
• Arrow keys move, Space or Enter cycles, S or 1 sets a sun, M or 2 a moon, Backspace or 0 clears
• H for a hint

Easy and medium grids are 6 by 6, and easy gives more symbols and signs. Hard grids are 8 by 8, and expert grids are 10 by 10 with few givens. Every puzzle has exactly one solution; up to hard, logic alone gets you there.

Is Duo free to play?

Yes. Duo is free in the browser with no account needed, no download and no ads. Your progress is saved on your device.

How do you play Duo?

Fill every cell with a sun or a moon. Each row and each column holds as many suns as moons. No more than two equal symbols may sit next to each other in a row or column. An = sign between two cells means they match; an × sign means they differ. Locked symbols are given. Every puzzle has exactly one solution.

How do the levels and difficulty work in Duo?

Easy and medium grids are 6 by 6, and easy gives more symbols and signs. Hard grids are 8 by 8, and expert grids are 10 by 10 with few givens. Every puzzle has exactly one solution; up to hard, logic alone gets you there.

Can I play Duo on my phone or tablet?

Yes. Duo works in any modern browser on phones, tablets and computers, with touch, mouse and keyboard controls.

Is there a daily Duo puzzle?

Yes. Every day there is a new daily puzzle, the same for every player, alongside unlimited numbered levels.