Always solvable by logic.
Diabolical Sudoku
No interrupting ads. No guessing, no brute force. 999 quiet, finely honed puzzles, polished by people who love sudoku.
Made for facing the board.
Your focus, unbroken.
No full-screen ads ever interrupt your play. Three levels — Hard, Harder and Demon. Just you and the board.
No guesswork.
No brute force, no lucky hunches. Every puzzle has a single solution and is built to be solved with step-by-step logic alone.
Stuck? One move at a time.
See the next move and the reason for it, step by step. You'll pick up the techniques naturally as you solve.
Think it, and it's on the board.
Pencil marks and placing digits, in a single touch. Choose digit-first or cell-first input — whichever suits you.
Where, and why,
it's settled.
Stuck? Open the explanation and go one move at a time. It names the technique you can use right now and shows, in color on the board, which candidates it removes. Read along, and that technique becomes yours for the next puzzle.
- Naked Single
- Hidden Single
- Locked Candidates
- Naked Pair
- Hidden Pair
- Naked Triple
- Hidden Triple
- X-Wing
- Skyscraper
- 2-String Kite
- XY-Wing
- XYZ-Wing
- W-Wing
- Swordfish
- Jellyfish
- Coloring
Opening an explanation uses tickets (earn them by watching an ad). Once opened, a puzzle's explanation can be viewed again for free.
Before you begin.
How much does it cost?
It's free, with all 999 puzzles included. A banner ad sits at the bottom of the screen, but no full-screen ads interrupt your play. You can remove the banner or unlock every explanation with in-app purchases.
How hard is it?
There are three levels: Hard, Harder and Demon. Demon puzzles call for techniques like X-Wing, XY-Wing and Swordfish. It's made for players who've outgrown easy sudoku.
Is every puzzle really solvable by logic?
Yes. Every puzzle has a single solution and is built to be solved through logical techniques alone, with no guessing or brute force.
What if I get stuck?
The explanation shows, one move at a time, which technique settles which cell. Opening an explanation uses tickets, which you can earn by watching an ad or buy. Once opened, a puzzle's explanation can be viewed again for free.
Is there a daily puzzle?
Yes — the Daily Challenge brings one Demon-level puzzle every day, the same puzzle worldwide on the same date. Track your streak on a calendar; on iPhone, Game Center leaderboards are supported too.
Is it available on Android?
Yes, it's on Google Play. It runs on iPhone with iOS 17 or later and on Android 8.0 or later, in 19 languages.
Start
Diabolical Sudoku.
Always solvable by logic. All that's left is for you to solve it.