Sun and Moon is a free logic puzzle in the Takuzu and Binairo family. Fill a 6 by 6 grid with suns and moons using a few clear rules, and every puzzle has exactly one solution. It runs in your browser with no download or sign up, works on phones and computers, and keeps working offline once loaded.
Inspired by: Takuzu and Binairo binary logic puzzles.
How to play Sun and Moon
- Tap a cell to place a sun. Tap again for a moon. Tap once more to clear it.
- No more than two suns or two moons may sit next to each other in a row or column.
- Every row and every column must have exactly three suns and three moons.
- A sign with two lines means the two cells have the same symbol. A cross sign means they are different.
- Fill the grid correctly as fast as you can. Hints add 15 seconds to your time.
Controls
- Mouse: Click a cell to cycle between sun, moon and empty. Click Undo, Hint or Clear below the grid.
- Touch screen: Tap a cell to cycle between sun, moon and empty. Tap Undo, Hint or Clear below the grid.
Tips to score higher
- Start with the equals and cross signs. They give you a free link between two cells.
- When two suns sit side by side, the cells on both ends must be moons.
- If a row already has three suns, fill all the other cells in that row with moons.
- Look for a pattern like sun, empty, sun. The middle cell has to be a moon.
- Red marks show a broken rule. Fix them before you carry on, or the puzzle will not finish.
The story behind Sun and Moon
Binary logic puzzles are part of the grid puzzle craze that began with Sudoku in the early 2000s. Takuzu and Binairo are names for the same kind of puzzle, with only two symbols, usually zero and one, and rules about balance and runs. They became popular in newspapers and puzzle apps because the rules fit in a few lines but the solving feels deep. Many people in India grew up solving newspaper puzzles on the commute or over a morning cup of tea. Sun and Moon dresses the same idea in friendly symbols, with a time to beat.
Questions players ask
Is Sun and Moon free to play?
Yes. It is free, with no sign up and no download.
Does every puzzle have only one solution?
Yes. The game builds each puzzle so that it can be solved by logic alone, with no guessing.
What is Takuzu?
Takuzu is a binary puzzle where you fill a grid with two symbols, with no three in a row and equal numbers in every line.
What do the equals and cross signs mean?
An equals sign means both cells have the same symbol. A cross means they are different.
What happens when I use a hint?
A hint fills in one correct cell and adds 15 seconds to your time.