Fillomino — a minimalist number-logic puzzle

Fillomino is a logic puzzle played on a grid: fill every empty cell with a number so that each connected group of matching numbers forms a region containing exactly that many cells. A group of 3s must span exactly three connected cells; a 1 always stands alone. Fillomino is one of the classic pencil-puzzle genres popularized by Nikoli, the Japanese puzzle publisher behind Sudoku, Kakuro, and Slitherlink — the rule set is simple to learn, but the puzzles get genuinely deep as the grid grows.

How to play

Darker cells on the board are given clues — fixed numbers you can't change. Every other cell starts empty, and your job is to fill each one so that every connected group of matching numbers is exactly the right size. A group of 3s must join together into exactly three connected cells; a 1 always stands alone with no neighbouring 1. Two separate groups of the same value can never touch, not even diagonally along a shared edge — if they did, they'd really be one larger group.

To fill a cell, tap a number in the toolbar to arm it — the button stays highlighted while armed — then tap any empty cell to paint that value. Tap the armed button again to disarm. For longer runs, press and drag across the grid to paint a whole line of cells with the armed value in one motion. Made a mistake? The eraser works the same way: arm it and tap or drag, or just long-press any single cell to clear it directly.

The checkmark button in the top bar highlights every cell that doesn't yet satisfy its region — either the group is the wrong size, or it's still empty — for about ten seconds, or until your next move. When a region is correctly filled, with the right number of connected cells and no conflicts, it turns green automatically. Fill every region on the board and the puzzle is solved. If you get stuck, undo steps back one move at a time, and a hint will reveal one cell that can be determined by logic alone — hints don't count against your solve time.

Puzzle sizes and difficulty

Nine grid sizes are available, from a quick 8×8 up to a substantial 16×16, each offered at easy, medium, and hard difficulty — 27 distinct puzzle banks in total. Larger, harder grids don't just add more cells: region sizes scale up too, so a 16×16 Hard puzzle can contain regions well into double digits, testing a different kind of spatial reasoning than the smaller boards.

Daily puzzles and streaks

A new daily puzzle unlocks every day at three of the nine sizes, so there's always a fresh, shared challenge to come back to. Solving each day's puzzle keeps your streak going — Fillomino tracks your current and longest streaks, and streak-related milestones (3-day, weekly, two weeks, monthly, and beyond) are among its achievements.

Achievements

Fillomino tracks progress across several categories as you play: solve-count milestones from your first puzzle up through a thousand solves, streak milestones, difficulty mastery (clearing medium and hard puzzles, and eventually every difficulty at every size), speed achievements for fast solves at each grid size, and a "no hints" category for players who prefer to work everything out by logic alone.

Frequently asked questions

Do I need an account to play? No — Fillomino is free to play in your browser with no sign-up required. Signing in is optional and syncs your progress and stats across devices.

What's a good strategy for beginners? Start by looking for 1s and cells that are already boxed in by clues on multiple sides — those have the fewest possible options and are usually where a puzzle's logic chain begins. Work outward from there rather than guessing at larger regions first.

Is Fillomino available as a native app? Yes — Fillomino is also available for iOS and Android, with the same puzzles, daily challenges, and progress sync as the web version.