Sudoku-ku

Sudoku, made for people who actually want to think. Five difficulty levels, from a relaxed Easy warm-up to a true Extreme mode built on genuine 17-clue puzzles — the mathematically-proven minimum for a uniquely solvable grid, not just a harder shuffle of the same generator. Every puzzle is checked to require real technique, not luck. SOLVE YOUR WAY Pencil marks with one-tap auto-notes, and notes clear themselves automatically as you fill cells in Unlimited undo and redo Mistake highlighting checks your entries against the actual solution, not just row/column/box duplicates Stuck? Hints explain the technique — naked single, hidden single, or the logical deduction that applies — and why that cell has to be that digit, so you learn something instead of just getting the answer DAILY CHALLENGE One shared puzzle every day, the same for everyone, with its own streak tracked separately from your regular games — see how many days in a row you can keep it going. MAKE IT YOURS 9 color themes, or follow your system's Light/Dark Mode automatically Colorblind-friendly mode adds clear badges to conflicts, no color-only cues Zen mode hides the timer when you just want to relax Track best times per difficulty and your win streak from the Stats screen FAIR HINTS, NO FORCED ADS Start with free hints on every puzzle. Need more? Watch a short optional video for one extra hint at a time — there are no banner ads, no interstitials, and nothing standing between you and a puzzle. Ads are entirely your choice. ACHIEVEMENTS Game Center achievements reward clean solves, quick times, personal bests, solving streaks, and milestones across every difficulty — pop your progress open anytime from Settings. Whether you're relearning the basics or hunting for puzzles that actually put up a fight, Sudoku gives you real difficulty, real explanations, and a board that stays out of your way.