Play Mosaic puzzle (Mosaic) online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
Mosaic is a shading puzzle: some squares carry a number from 0 to 9, which tells you how many black squares are in the 3×3 block centred on it, the clue square included. Use the clues to colour every square black or white. It appears elsewhere under names such as Mosaico and Count and Darken. The puzzle is ready below; click a square to shade it.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Shade a square black | Arrow keys to move, Enter | Left-click (keep clicking to cycle) |
| Mark a square white | Space | Right-click (keep clicking to cycle) |
| Reset a square | Backspace | Cycle back to empty |
| Colour several squares | — | Hold the button and drag |
| Undo / redo | U / R (or Ctrl+Z / Ctrl+R) | Game menu buttons |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Mosaic is from Simon Tatham's Portable Puzzle Collection, © Simon Tatham and contributors, used under the MIT licence. Built from source by scripts/build-puzzles.mjs.
How to play
- Every square ends up black or white.
- A number counts the black squares in the 3×3 area around and including it. Along the edges and corners that area is smaller.
Sizes and difficulty
The Type menu offers square boards of 3×3, 5×5, 10×10, 15×15, 25×25 and 50×50. Custom also sets aggressive generation, which removes more unnecessary clues and makes puzzles harder but slower to build.
Solving tips
Start with 0s and 9s, which settle their whole block, and with clues that match the size of their area at an edge (a 4 in a corner, a 6 on a side). Then compare overlapping clues: two neighbouring numbers share six squares, so the difference between them tells you about the three squares only one of them sees. Mark whites as carefully as blacks.
Where this puzzle comes from
Mosaic is part of Simon Tatham's Portable Puzzle Collection, a set of about forty logic puzzles written by Simon Tatham and contributors and released under the MIT licence. Every grid is generated on the spot, so the supply never runs out, and for the grid-logic puzzles the generator makes sure each has exactly one solution, reachable by reasoning rather than guessing. The version here is the collection's own code compiled to WebAssembly; the Game menu can save a puzzle to a file and load it again, and the Type menu changes the size and difficulty.
Frequently asked questions
Does the clue square count itself?
Yes. The 3×3 area includes the numbered square, so a 9 means all nine are black, the number's own square included.
What happens at the edges?
The area is cut off by the border, so a corner clue covers only four squares and an edge clue six.
Is Mosaic free to play here?
Yes, with no limit on the number of puzzles. Mosaic is open-source software under the MIT licence, and every grid is generated fresh when you press New game.
Does it work on a phone or tablet?
Yes. A tap works as a click and the puzzle resizes to fit the screen. Puzzles whose controls use the right mouse button are easier with a mouse.
More you can play in your browser
Related guides
- Nonogram (Pattern)Play nonograms free in your browser: shade the grid so each row and column matches its run
- Light Up puzzle (Light Up)Play Light Up free in your browser: place bulbs so every white square is lit, no bulb shin
- MinesweeperThe Minesweeper you remember — three board sizes, chording, first click always safe. Insta
- Range puzzle (black cells) (Range)Play Range free in your browser: blacken squares so each number sees exactly that many whi
Want a game like this on your own site?
Mosaic puzzle (Mosaic) isn't ours to give away — we host it, we didn't write it. But eleven of the games here we did write from scratch, and those are free for anyone to put on their own page: one line of HTML, no account, no permission, no attribution beyond a credit line.