DELTA — a Fillomino logic puzzle for Android

Count the heat. Pure deduction, no guessing.

What is DELTA?

DELTA is a free Fillomino puzzle app for Android — the classic Japanese number-grid logic puzzle, redesigned on a thermal-color grid. Cells with the same value that share an edge form a region, and every region must contain exactly as many cells as the number it shows. Two regions of the same size can never touch.

If you enjoy Sudoku, Nonograms, or Picross but want something fresh, Fillomino is the next logic puzzle to learn — and DELTA is built so every puzzle can be solved by pure deduction. There is always a logical next move; you never have to guess.

Screenshots

DELTA gameplay — solving a 9×9 Fillomino logic puzzle on a thermal-colored grid — Every number is the size of its region

How to play

Boards range from a small 6×6 Beginner grid up to the 9×9 tiers. A handful of pre-filled numbers seed the deduction.
Same-value cells that share an edge group into a region. A region showing 4 must contain exactly 4 cells.
Two regions of the same size can never share an edge.
Tap a blank cell and pick a number from the thermal palette. Fill only cells you can prove — never guess.
Stuck? ANALYZE flags rule violations so you can learn the deduction techniques as you play.

Features

Six tiers — a 6×6 Beginner warm-up plus five 9×9 tiers, from Easy (50% pre-filled) down to Master (14%)
Skill-based progression — the Beginner warm-up unlocks Easy, then about 50 solves to climb each 9×9 tier (no paywall)
Daily DELTA puzzle with streak tracking
Built-in ANALYZE solver for learning Fillomino techniques
Thermal, colorblind-safe, and premium color themes
Plays fully offline — no account required, no subscription

FAQ

What is a Fillomino puzzle?: Fillomino is a Japanese grid-deduction puzzle: divide the grid into regions so that each region of size N contains only the number N, and no two same-size regions touch edge-to-edge. DELTA follows these classic rules with a thermal-color twist.
How hard is DELTA, and how do tiers unlock?: New players start on a small 6×6 Beginner board to learn the rule, then unlock five 9×9 tiers — Easy, Medium, Hard, Expert, and Master. Progression is by skill, not payment: clear the Beginner warm-up to reach Easy, then solve about 50 puzzles to climb each tier.
Is DELTA free?: Yes — DELTA is free to download and play on Android, with optional cosmetic themes and hints.
Do I need an internet connection?: No. Every puzzle plays fully offline. You only need a connection to download the app.
Does DELTA ever require guessing?: No. Every puzzle is generated with a unique solution reachable by logic alone — there is always a provable next move.
Is DELTA on iPhone?: An iOS version is coming to the App Store. It's available now on Android via Google Play.