What is fillomino?
Fillomino is a number puzzle about regions. The grid starts with a few numbers, and you fill in the rest. When you are done, the squares form groups, and each group of matching numbers must be exactly as big as its number: a single 1, a pair of 2s, three 3s joined together, and so on. Two groups with the same number can never touch side by side.
The rules are short, but the grids get surprisingly deep. Play fillomino online free here on three sizes, from a 9×7 starter to a big 17×13 board.
Where fillomino comes from
Fillomino comes from Nikoli, the Japanese publisher behind many classic logic puzzles. The name joins “fill” with the “-omino” of domino and polyomino, because the finished regions are polyominoes: shapes made of squares joined edge to edge. You may also see it called Filling.
How to play here
Pick a size on the start card, then press Play. Click or tap an empty square and type a digit, or use the number pad on a phone. To fill several squares with the same number, drag across them first and then type the digit once. To clear a square, select it and press 0, Space or Backspace, or use Undo.
Undo, Redo and New puzzle are in the dock. The pause menu has Restart, Solve and Enter game ID.
Clues that don’t belong to one region
A detail that trips up beginners: a clue doesn’t have to be the only clue in its region. Two 4s on the board might sit in the same region of four squares, or in two separate regions. And some regions have no clue at all, so empty areas can be filled with any numbers that fit the rules.
That’s why the most useful questions are about space. How many squares can this region still reach? Which empty pockets are too small for any nearby number to grow into?
A step-by-step way to solve
- Finish what is already finished. A clue of 1 is complete. Two 2s side by side are complete. Close them off.
- Grow regions with one exit. If a region still needs squares and has only one free neighbor, it must grow there.
- Separate equal numbers. If two unconnected clues with the same number would join into one oversized region, the square between them needs a different number.
- Fill small pockets. An isolated single empty square surrounded by completed regions is a 1. A walled-in two-square pocket is a pair of 2s.
Why play fillomino?
Fillomino mixes number logic with shape building, so it feels fresh even if you play a lot of sudoku. Every board has a unique answer. If you enjoy it, try Shikaku, which also splits a grid into sized regions, or Galaxies.
How to play Fillomino
- Some squares start with a number. Fill every empty square with a digit from 1 to 9.
- Squares with the same number that touch side by side form one region.
- Each region must contain exactly as many squares as its number: a region of 3s has three squares, a region of 5s has five.
- Two regions of the same number may not touch along an edge, or they would merge into one region that is too big.
- Squares that only touch at a corner are not in the same region.
Fillomino tips
Fence in the finished regions
When a region reaches its size, none of the squares around it can hold the same number. That often decides what a neighbor must be.
Look at small pockets
An empty pocket of two squares walled in by finished regions must be a pair of 2s, because two 1s can't touch. Small spaces leave few choices.
Give big numbers room
A 6 tucked in a corner needs five more squares. If there's only one direction it can grow, extend it that way.
Frequently asked questions
How do you solve fillomino?
Start with the clues that are nearly complete or boxed in, such as a 2 with only one free neighbor. Extend regions where they have only one way to grow, and close off finished regions so the same number can't touch them.
Is Filling the same puzzle as fillomino?
Yes. Filling is another name for fillomino. The rules are the same, so a puzzle labelled Filling plays exactly like this one.
Can the same numbers touch diagonally?
Yes. Diagonal contact doesn't join squares into a region, so two separate regions of 3s may meet at a corner.
Can a region be bigger than 9?
No. Each square holds a single digit, so the largest possible region has nine squares. There are no zeros either.
