What Is Fillomino? Rules, Regions, and Beginner Tactics

What is Fillomino, exactly?

What is Fillomino? It is a region-building logic puzzle where you carve a grid into blocks whose sizes are dictated by the numbers already printed inside them. Every number tells you how big the region it belongs to must be, so a five sits in a region of exactly five connected cells, and a three sits in a region of exactly three. Many cells start blank, and part of the fun is deciding which region each blank cell joins. Fillomino has a satisfying jigsaw quality, because you are not placing symbols so much as drawing borders that make every count come out right. It is a gentle, meditative puzzle that still hides plenty of clever forced moves for solvers who look closely.

The rules of Fillomino

The rules of Fillomino are elegant. The grid is divided into regions of connected cells, where connected means joined edge to edge, and every cell in a region shares the same number. That number equals the total number of cells in the region, so a region labeled four is made of four connected cells all showing four. Blank cells must be filled in with numbers so that the whole grid is covered by valid regions. The one extra rule does the heavy lifting: two regions of the same size may not touch along an edge. If two cells with the same number sit next to each other, they must belong to the same region, not two separate regions of that size. That single restriction turns a loose counting task into a tight logical one.

Here is a worked example. A cell showing one is a region all by itself, so none of its four orthogonal neighbors may also be a one, or they would form a forbidden same-size neighbor. A cell showing two must pair with exactly one adjacent cell to complete a region of two, and you have to choose the neighbor that does not break another region. Now suppose two threes sit side by side. Because equal numbers that touch must share a region, those two threes are part of the same trio and need exactly one more connected cell showing three to finish. Working outward from small numbers like these, you fill blanks and draw borders until every region reaches its exact required size.

Beginner tactics for Fillomino

• Start with ones, since each is a complete region and immediately forbids its neighbors from being ones as well.
• When two equal numbers touch, join them into the same region rather than treating them as separate same-size blocks.
• Use the no-touching rule for equal sizes to wall regions off and eliminate impossible extensions.
• Count as you build; a partly formed region needs exactly its number of connected cells, no more and no fewer.
• Fill blank cells by asking which nearby region still needs to grow to hit its target size.

How Fillomino compares to Sudoku

Compared with Sudoku, Fillomino shifts your focus from symbols to shapes and sizes. Sudoku asks you to place each of nine symbols exactly once in every row, column, and box, all through elimination, while Fillomino asks you to partition the grid so every region matches the number it contains. Both are guaranteed to have a single answer and both reward patient, guess-free reasoning. If Fillomino leaves you craving more clean, rule-driven logic, Shapedoku offers a warm return to classic Sudoku with a twist: the numbers one through nine become nine glowing shapes, so you solve by color and form instead of digits. Designed to be colorblind-friendly and relaxing, Shapedoku gives you a free solver and printable boards at shapedoku.com, plus instant play in your browser at app.shapedoku.com whenever you want a calm puzzle.