A comprehensive, fully offline Sudoku app that doesn't just let you play — it teaches you how to think. Built with every known solving strategy, a multi-layer hint system, and no tracking, no ads, no internet required.

• Smart Puzzle Generation — Puzzles are generated on the fly across 6 difficulty levels, tuned by the solving strategies required — not just the number of givens.
• Full Solving Engine — Implements all 27 known Sudoku solving strategies, from naked singles to forcing chains, ALS, and Sue de Coq.
• Multi-Layer Hints — Hints guide your thinking, not hand you answers. From a gentle nudge ("look for 3 in box 4") to a strategy suggestion to the exact answer — each layer requires a deliberate long-press.
• Interactive Strategy Guide — Step-through walkthroughs for all 27 strategies with narrated example boards showing highlights, eliminations, and placements. Plus a beginner-friendly "How to Solve Sudoku" guide.
• Training Games — Bite-sized drills to build Sudoku reflexes. Number Rush (find the missing digit against the clock) and Where Does N Go? (spot the only cell for a digit on a full board). Three modes each with personal leaderboards.
• Puzzle Analysis — Full solve breakdown showing which strategies are needed at every step, with a solve-order heatmap and bottleneck identification.
• Pencil Marks & Undo/Redo — Full note-taking with auto-fill (long-press Notes) and move history support.
• Number-First & Erase-First Input — Tap a digit then tap cells to fill, or toggle erase mode for quick corrections.
• PDF Export — Generate puzzles in bulk with optional rough work grids, solve-order hints at the back, and QR codes to open each puzzle in the app.
• QR Scanner — Scan printed puzzle QR codes to play them interactively.
• Themes & Customization — Dark, AMOLED, and light themes with 9 accent colors. Two board layouts: Circular (modern) and Classic (traditional). Smooth gameplay animations (togglable).
• Player Stats — Track solve times, streaks, completion rates, and detailed hint usage with per-difficulty leaderboards.
• Save & Bookmark — Save in-progress puzzles, bookmark favorites, and export/import all your data as JSON.
• CLI App — A standalone command-line interface with TUI and classic modes.

sudoku/
├── packages/
│   └── sudoku_core/          # Pure Dart — all game logic
│       ├── lib/src/
│       │   ├── models/       # Board, Cell, Puzzle, Move, Difficulty
│       │   ├── generator/    # Puzzle generation with difficulty targeting
│       │   ├── solver/       # 27 solving strategies + backtracking
│       │   ├── hint/         # Multi-layer hint engine
│       │   └── stats/        # Stats, persistence, data export
│       └── test/
├── apps/
│   ├── flutter_app/          # Flutter UI (all platforms)
│   └── cli/                  # Terminal app (TUI + classic modes)
├── PROJECT_SCOPE.md
└── PLAN.md

• Flutter SDK (3.11+)
• Dart SDK (3.11+, included with Flutter)

cd apps/flutter_app

# Run on your current platform
flutter run

# Or build a release
flutter build macos    # or apk, ios, windows, linux

cd apps/cli

# Run directly
dart run bin/cli.dart

# With a specific difficulty
dart run bin/cli.dart -d hard

# Compile to standalone binary
dart compile exe bin/cli.dart -o sudoku
./sudoku

See CLI README for full command reference, key bindings, cross-compilation, and Homebrew setup.

# Core logic tests
cd packages/sudoku_core
dart test

# Flutter app tests
cd apps/flutter_app
flutter test

Difficulty is determined by the most advanced solving strategy required — not by the number of givens. Strategies are weighted by how hard they are for humans (e.g., hidden singles are easier to spot than naked singles because you just scan a house for where a digit fits).

Zero data collection. No accounts, no telemetry, no third-party scripts. Everything runs locally on your device.

GPLv3