Sudoku that teaches you why.
Inkdoku is a calm, classic sudoku. Pen for answers, pencil for notes, and when you get stuck, a hint that shows the next logical step and explains it. Every puzzle has exactly one solution, full-screen ads never appear while you solve, and a new puzzle waits every morning.
Get it on Google Play
Hints that explain why
Tap Hint to see the next logical step and the reason: only one spot in a box, only one number for a cell, locked candidates, naked pairs.
No guessing, ever
Every puzzle is built by a logic solver, so there is exactly one solution and you can always reach it by reasoning.
Five honest levels
Easy, Medium, Hard, Expert and Master are graded by the techniques you need, not just the number of clues.
No pop-ups mid-puzzle
Full-screen ads only appear between games. A small banner stays at the bottom, away from the number keys.
A new puzzle every morning
Solve today's sudoku to grow your streak, and see every day you played on a monthly calendar.
Pencil notes that clean up
Pencil in candidates, and when you write a number it is removed from notes in the same row, column and box.
Your way of solving
Mistakes are not marked in red unless you turn it on. Hide the timer, turn off highlights or use larger numbers.
Private and offline
No account, works offline, light and dark themes, and a home screen widget for today's puzzle.
FAQ
- Is Inkdoku free?
- Inkdoku is free to download and every level, hint and the daily puzzle are included, with no subscription. It is supported by ads that appear between games, never while you are solving.
- Do I ever have to guess?
- No. Every puzzle has exactly one solution and can be solved with logic alone. If you are stuck, a hint shows the next step that follows from what is already on the board.
- What is the difference between the levels?
- Levels are graded by technique. Easy needs only hidden singles, Medium adds naked singles, Hard needs locked candidates, and Expert and Master need naked pairs with fewer clues.
- Will it mark my mistakes in red?
- Not by default, so you can think it through. If the board is full and something is wrong, the wrong cells are marked. You can turn on instant checking in Settings.
- How do pencil notes work?
- Turn on Notes and tap numbers to write small candidates in a cell. When you write a number in ink, it is cleared from the notes in the same row, column and box.
- Does it work offline?
- Yes. Puzzles are generated on your phone, so you can play anywhere without an internet connection.
- Will I lose my game if I close the app?
- No. Every move is saved on your phone, so you can continue exactly where you left off.
- Do I need an account?
- No account and no sign-up. Your games, streak and times stay on your phone.