How to Play Grey Is Odd

Core rules

• Each row and column must contain exactly the number of dots shown by the hints.
• Grey regions must contain an odd number of dots.
• White regions must contain an even number of dots.
• Click a cell to cycle: empty → dot → cross.

Note: 0 is even, so a white region may contain 0 dots. Regions can contain zero dots if all constraints allow it.

What the symbols mean

Dot This cell contains a dot.
X This cell is definitely empty (no dot).
Empty Not decided yet.

Quick deduction tips (no spoilers)

• If a row says “0”, mark every cell in that row with an X.
• If a row says “N” and the row has N cells, every cell must be a dot.
• Use region parity together with row/column counts: parity often forces the last few cells.

For deeper techniques (like “Gulf”), open Tips & Tricks inside the game.

Video tutorial

A short walkthrough of the rules and the basic interaction.

FAQ

Is 0 even? Yes. 0 is even.

Can a region have 0 dots? Yes — white regions can, if the constraints allow it. Grey regions cannot, since they must contain an odd number of dots.

Do I need to guess? No. The puzzles are designed to be solvable by deduction alone.

How do I know if I solved the puzzle? When the puzzle is solved, a victory message appears and the dots animate.

Do I need to submit my solution? No. The puzzle checks itself automatically as you play.

What do the symbols mean? A dot means a filled cell. An X means empty and does not count as a dot.

I solved all rows and columns, but nothing happens. Why? Row and column clues are necessary but not sufficient — all odd/even region rules must also be satisfied.

I’m stuck — what should I do? Open Tips & Tricks in the game for proven solving patterns.