Every variant, one app.
Killer, thermo, arrow, Kropki, German whispers, XV and more — on 4×4, 6×6 and 9×9 boards. Two new dailies every day, a hint engine that teaches real techniques, and offline solving. No ads, no trackers.
- Free on iPhone, iPad & Android
- Every puzzle logic-checked
- Hints from your own pencil marks
Today's dailies
The fastest clean solves of today's 4×4 and 6×6 dailies in the app.
Learn the variants
Plain-English rules, reference tables and step-by-step techniques — drawn exactly the way the app's hints show them.
Killer Sudoku
Cages with target sums turn classic sudoku into an arithmetic puzzle. Includes a full cage combinations chart for every 2–5 cell sum.
Thermometer Sudoku
Digits climb from bulb to tip. Includes a range table giving the highest possible bulb and lowest possible tip for every thermometer length.
Arrow Sudoku
A circle holds the sum of the digits along its arrow. Includes a shaft-length table showing which arrows are even possible.
Kropki Sudoku
Kropki is Polish for “dots”. White marks consecutive digits, black a 1:2 ratio — small marks, big chains of logic.
X-Sudoku (Diagonal Sudoku)
Add two diagonals to a classic grid and the whole solve tightens. The friendliest entry point into variants.
Renban Sudoku
A renban line holds consecutive digits in any order. Includes a run table listing every set each line length can hold.
Between Line Sudoku
Digits on the line fall strictly between the two circled ends. Includes an endpoint table showing how many cells each gap can carry.
Anti-Knight Sudoku
No digit may repeat a chess knight's move away. Includes the eight-offset move map and the eliminations it creates.
Palindrome Sudoku
The line reads the same both ways, mirroring digits across its centre. Includes a pairing table for every line length.
German Whispers Sudoku
Neighbouring digits on the line differ by at least 5. Includes a partner table — and the reason 5 can never appear.
XV Sudoku
X marks a pair summing to 10, V marks a pair summing to 5. Includes the full pair table and the negative-constraint rule.
Mini Sudoku (4×4 and 6×6)
4×4 and 6×6 boards keep the variant rules but change the numbers. House totals, box shapes and a cheat sheet for every variant.
Hints that teach the next deduction
The hint engine solves the way a person does. It starts from your own pencil marks and shows one logical step at a time — which constraint applies, which candidates it removes and why.
- Variant-aware. Cage combinations, renban windows, Kropki pairs, whispers bands and more — not just classic techniques.
- Step by step. Each card names its technique, from hidden singles to X-Wings and short forcing chains.
- Never a guess. Every step is checked against the solution before it is shown.
What's inside
Built for variants
Killer, thermo, arrow, German whispers, XV, Kropki and 20+ other rules are first-class, on 4×4, 6×6 and 9×9 boards. Every puzzle is logic-checked and has exactly one solution.
Hints that teach
Stuck? The hint engine reads your own pencil marks and walks you through the next deduction step by step — the same techniques this site's guides explain. Never just a digit.
Two dailies and a leaderboard
A new 4×4 and 6×6 daily every day, ranked by clean-solve time on Game Center and Google Play Games. Come back daily and climb.
Offline solving
Solve anywhere. Progress, pencil marks and full undo history stay on your device — no connection needed.
No ads, no trackers
Free to play, with an optional Variant+ subscription for unlimited puzzles. Your gameplay is never sold or turned into ad targeting.
Search that gets it
Find puzzles by rule, size or theme. Search understands “killer with thermos” or “gentle arrow”, not just exact tags.
Play today's two dailies
A new 4×4 and a new 6×6 puzzle every day, each with its own leaderboard — plus a catalog of thousands more. Free on iPhone, iPad and Android.
Acknowledgements
Puzzle generation, validation, and difficulty research use CP-SAT techniques.
Shout-out to Logic Masters Germany, Sven from SudokuPad, and Cracking the Cryptic for their influence on the variant sudoku community.