Sudoku Calm: Classic Puzzles

Sudoku Calm is classic 9×9 Sudoku on a quiet sheet of paper. Fine ink grid lines, clear serif digits and nothing flashing for your attention: just you, the puzzle and a few unhurried minutes.

EVERY PUZZLE HAS ONE ANSWER
Puzzles are generated on your phone, and every one is checked to have exactly one solution. Each difficulty is graded by the techniques it needs, not just by how many digits are missing:
• Easy: a gentle start, solvable with singles
• Medium: fewer clues, steady solving
• Hard: needs pointing pairs and naked or hidden pairs
• Expert: triples, X-Wings and XY-Wings

A DAILY PUZZLE
One new puzzle every day, the same for everyone. Solve it to press a vermilion seal on your calendar and keep your daily streak going. Missed a day? Tap it in the week strip to play any of the last seven daily puzzles. A late solve is sealed in outline and kept outside the streak.

TOOLS THAT STAY OUT OF THE WAY
• Pencil notes, with notes cleared automatically when you place a digit nearby
• Pencil tools: fill in every possible digit, tidy notes that no longer fit, or clear them all, each as one step you can undo
• Mistake checking your way: a limit of three, show mistakes without a limit, or off, with a one-tap "Check my digits"
• Matching digits and clashes are shaded so you can see the board at a glance
• A large digits option for easier reading
• Unlimited undo
• Hints that point to the next logical step and explain it, such as "4 has only one place left in this box"
• A timer that pauses whenever you leave the app

YOUR PROGRESS
Statistics for each difficulty: games played and won, best and average time, perfect solves and win streaks, plus a calendar of every daily puzzle you have sealed.

Optional Premium (one-time purchase): no ads, with unlimited hints and second chances; Night paper, a true dark theme; two new kinds of puzzle, Extreme (beyond X-Wings) and Diagonal (both long diagonals hold 1 to 9 too); a daily archive to play any daily puzzle from the past year; and your solve history, with a chart of recent times, your fastest five and averages for each level. It is a single purchase with lifetime access, not a subscription. Everything else described here stays free.

GOOD TO KNOW
• Works fully offline, no account needed
• Your games are saved automatically on your device
• Supported by ads. Each puzzle includes one free hint; you can watch a short ad for another hint or for a second chance after three mistakes. Those ads only play when you tap a button that says so.
• Sound and vibration can be turned off in Settings