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
- 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 to play, step by step
- Balance the grid. Every row and column needs as many suns as moons, and never three equal symbols in a line.
- 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.
More puzzles in Axiom
Axiom MergeSlide, merge, charge and set off chain reactions.
Block ArchitectFit polyomino pieces into a shaped board.
Circuit FlowRotate tiles until every lamp is lit.
Logic GridReveal a hidden picture from number clues.
Shift LabPush blocks onto targets without trapping them.
Axiom SudokuFill the grid so no digit repeats in a row, column or box.
Axiom MahjongMatch pairs of open tiles until the board is clear.
Axiom SpectrumPour colored layers until every tube holds one color.
Axiom TacticsFind the winning move in real chess positions.
Axiom Mind LabFive kinds of reasoning puzzles, each with a clear explanation.
Axiom Word SearchFind every hidden word in a grid of letters.
Axiom PathDraw one line through every cell, numbers in order.
Axiom DominoPlace every domino so each region meets its rule.
Axiom JamSlide each block out through the gate of its colour.
