Guide
How to play sun & moon puzzles
Three rules, five techniques, zero guessing. This guide covers everything from your first tap to the line-enumeration logic that cracks hard boards.
The three rules
- 1 · Balance Every row and column contains exactly three suns ☀️ and three moons 🌙.
- 2 · No triples Three identical symbols can never sit together in a line — ☀️☀️☀️ is always illegal.
- 3 · Signs An = between two cells means they match. An × means they differ.
This rule set is shared by a whole family of binary puzzles — Binairo, Takuzu, and the tango-style games you may know from LinkedIn. Learn it once and you can play them all.
Technique 1 — Chase the signs first
Signs are free information. The moment one cell of an = pair is known, the other is identical; the moment one cell of an × pair is known, the other is its opposite. Sign chains can cascade: one placement flows through =, flips through ×, and fills three or four cells in a row. Always start a puzzle by walking every sign connected to a given symbol.
Technique 2 — Split the pairs
Two identical symbols side by side (☀️☀️) force both neighbors to be the opposite (🌙☀️☀️🌙). The moment you place a pair, cap both ends immediately — this is the single most common deduction in the game.
Technique 3 — Fill the sandwich
Two identical symbols with a gap between them (☀️_☀️) force the middle cell to be the opposite, because filling it identically would create an illegal triple. Scan every row and column for these X-gap-X patterns after each move.
Technique 4 — Count the line
The moment a row or column reaches three of one symbol, every remaining empty cell in that line must be the other symbol. Count constantly: a line with three moons placed is a line you can finish instantly.
Technique 5 — Enumerate the line (hard boards)
When basic rules stall, pick a nearly-complete line and mentally list every legal way to finish it — respecting the 3/3 balance, the no-triples rule, and any signs inside the line. If a cell takes the same symbol in every legal completion, that symbol is certain. This deeper technique is what separates hard boards from medium ones, and it never requires guessing — just patience.
A worked opening
Say row 1 starts with a given ☀️ in column 2 and an = sign between columns 2 and 3. Technique 1 makes column 3 a ☀️. Now columns 2–3 are a sun pair, so Technique 2 caps both sides: columns 1 and 4 become 🌙. That's four cells from one given — and the cascade usually continues down the columns you just filled.
Ready to play?
Put the techniques to work on today's daily puzzle, practice on unlimited boards in three difficulties, or revisit any past daily in the archive. Stuck mid-game? The hint button doesn't just fill a cell — it names the technique that proves it.