Sudoku - Think & Solve

No ads. No tracking. No internet. Just Sudoku. A Sudoku app built by a Sudoku nerd, for Sudoku nerds. Every puzzle is generated on the fly, graded by the solving strategies it requires — not just the number of empty cells. From beginner to master, you'll always get a fair challenge. Smart Hints That Teach You Most apps just hand you the answer. This one doesn't. Hints are layered — start with a gentle nudge ("look for 7 in box 3"), then a strategy suggestion ("try X-Wing on rows 2 and 7"), and only reveal the full answer if you really want it. Each layer requires a deliberate long-press. Your effort is respected. Every Strategy, Implemented The solving engine covers all 27 known Sudoku techniques: - Naked & Hidden Singles, Pairs, Triples, Quads - Pointing Pairs & Box/Line Reduction - X-Wing, Swordfish, Jellyfish - XY-Wing, XYZ-Wing - Simple Coloring, X-Chains, XY-Chains - Unique Rectangles, ALS, Sue de Coq, Forcing Chains & more Interactive Strategy Guide Step-through walkthroughs for all 27 solving strategies, grouped by difficulty. Each walkthrough has a narrated example board showing highlights, eliminations, and placements — so you actually learn how each technique works. Plus a beginner-friendly "How to Solve Sudoku" guide for getting started. Training Games Build your Sudoku reflexes with bite-sized drills: - Number Rush — Eight digits shown, find the missing one. Race the clock across Chill, Quick, and Sprint modes. - Where Does N Go? — A full board, one digit, one cell. Find where it goes by elimination. Track your streaks and compete against your own top 10 leaderboard for each game and mode. 6 Difficulty Levels Beginner → Easy → Medium → Hard → Expert → Master Each level is defined by which techniques you'll need — so "Hard" actually means hard. Puzzle Analysis Run a full solve breakdown on any puzzle to see exactly which strategies are needed at every step. PDF Export Generate puzzles in bulk and export as PDF for printing. Includes optional rough-work grids, solve-order hints at the back, and QR codes to open any puzzle in the app. Track Your Growth Detailed stats track solve times, streaks, completion rates, and exactly which hints you used — so you can see which strategies you're mastering and where you need practice. Per-difficulty leaderboards let you track your best times. Themes & Customization - Dark mode, AMOLED black, and light themes - 9 accent color presets - Two board layouts: Circular (modern) and Classic (traditional) - Smooth gameplay animations (togglable) Full-Featured Gameplay - Pencil marks & candidate notes (with auto-fill) - Undo / Redo - Number-first input — tap a digit, then tap cells - Erase-first mode for quick corrections - Save & resume, bookmarks - Export & import all your data as JSON - Inspirational quotes on the puzzle screen Open Source The entire source code is public. No secrets, no hidden tracking. GPLv3 licensed. https://github.com/vivekg7/sudoku