Sudoku Ultimato

Jan 2026

Sudoku Ultimato started for a simple reason. My dad wanted to play Sudoku without subscriptions, pop-ups, or constant interruptions. At the same time, I was getting tired of ads, locked features, and missing game modes in most Sudoku apps. I wanted Killer Sudoku, different board sizes, landscape support, and proper statistics. So I decided to build it myself.

What began as a small personal project grew into a full mobile app. Along the way, I learned Android development, built online leaderboards, and figured out how to ship the same app to iOS and Android from one codebase.

Sudoku Ultimato is meant to feel quiet and flexible. You can play a quick puzzle on a small grid or spend more time on a large board. Switching between Classic and Killer mode is easy, and accessibility options like zoom and larger text are there if you need them. Daily puzzles add something new each day, while Killer cages give extra challenge for players who enjoy deeper logic.

Main features

Classic Sudoku and Killer Sudoku
Endless puzzles generated instantly from seeds
Daily challenge mode
Board sizes 4×4, 9×9, and 16×16
Light and dark themes
Accessibility options such as zoom, text size, and haptics
Landscape support on phones and tablets
Fast input with minimal distractions
Limited and non-intrusive ads
Available in English, Dutch, Thai, German, French, Portuguese, and Italian
Available on the App Store and Google Play

How it is build
The app is built with Flutter, using one shared codebase for iOS and Android. Firebase is used for authentication, analytics, leaderboards, and syncing player statistics between devices.

Each puzzle is generated and solved using custom Dart logic. A seed system stores the puzzle setup, including board size, game mode, difficulty, and puzzle number. This makes it possible to replay the same puzzle or compare results across devices.

The product website is built with Next.js and Tailwind CSS and is deployed as a static site with multi-language support.

Flutter
Figma
NextJS
Dart
iOS
Firebase
Android
Tailwind CSS