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Binary logic

Axiom Duo

Fill a square grid with suns and moons. Every row and column holds as many of each, no three equal symbols touch in a line, and the = and × signs tie neighbours together. Each grid has exactly one answer, waiting to be deduced.

Free in the browser, no account needed.

Rules

  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.

How to play, step by step

  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.

Controls

  • 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

Difficulty and levels

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.

Axiom Duo: frequently asked questions

Is Axiom Duo free to play?
Yes. Axiom Duo is free in the browser with no account, no download and no ads. Your progress is saved on your device.
How do you play Axiom 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 Axiom 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 Axiom Duo on my phone or tablet?
Yes. Axiom Duo works in any modern browser on phones, tablets and computers, with touch, mouse and keyboard controls.
Is there a daily Axiom Duo puzzle?
Yes. Every day there is a new daily puzzle, the same for every player, alongside unlimited numbered levels.

Play Axiom Duo

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