Nice Sudoku is a full-featured Sudoku application built for people who are serious about learning, and playing Sudoku.

Started life as a “Learn Godot” project. Evolved into a “Learn Sudoku by writing solvers”.
Then Stage 2, teaming up with StrmCkr, using his solver, a “Learn Kotlin” project.
It has a unique play style, that we just adore!

Nice Sudoku Features

Powerful Puzzle Solving Tools

• Smart Highlighting System — Four distinct modes to visualize patterns and eliminate possibilities
• Pencil Marks & Candidates — Track possible values with auto-calculation or manual entry
• Hint System — Learn solving techniques with intelligent hints (requires backend)
• Mistake Detection — Catch errors in real-time or verify candidate eliminations

Multiple Play Modes

• Fast Mode — Select number first, then place. Perfect for speed solving
• Place Mode — Select cell first, then enter the number. Methodical and precise
• Multi-Select Mode — Bulk manage pencil marks across multiple candidates

Flexible Gameplay

• 8 Difficulty Levels — From Beginner to Diabolical with hundreds of puzzles each
• Resume Anytime — Save progress automatically and pick up where you left off
• Play Time Tracking — Optional elapsed time counter for personal challenges
• Progress Statistics — Track mistakes, hints used, and completion percentage

Customization & Accessibility

• 4 Themes — Dark, Blue, Light, and E-Paper modes
• Multi-Language Support — Play in your preferred language
• Full Keyboard Shortcuts — Navigate and solve using only your keyboard (HoDoKu-compatible)
• Responsive Design — Works seamlessly on desktop and mobile

Import & Export

• Save & Load — Preserve your game state with all progress
• Import Puzzles — Load custom puzzles into your library