Made for curious minds · Free on Android

Cryptic: Sudoku & 17 Variants

Cryptic is a sudoku app with 17 variants, from Classic and Killer to Thermo and Miracle, plus a Technique Academy that teaches 25 solving techniques.

Get it onGoogle Play Play on the web

Free to download. No account required. Ages 13+.

17ways to solve

25techniques taught

5practice boards per technique

A Thermo sudoku puzzle in the app, with thermometer paths, a number pad, and Undo and Redo controls. — Thermo Sudoku · Actual gameplay

Four familiar faces

Meet your owl companions

Browny

Thinking

Named for Athena, the Greek goddess of wisdom.

Bradchad

Practising

Named for Apollo, the Greek god of music and light.

Bubblegum

Singing

Named for Aoide, one of the first Muses of song.

Sleepy

Dozing

Named for Hesychia, the Greek spirit of quiet and stillness.

Learn the rule. Find the next step.

Why do solvers switch to Cryptic?

01 / Learn

A guide for every variant

Interactive guided lessons teach every single variant. Professor Cryptic helps you understand the logic beyond random cell hints.

Start with guided 4x4 beginner lessons. Then work through the 9x9 variants at your own pace.

02 / Solve

Tools for your next deduction

Use Corner & Centre notes. Auto-clearing notes keep your candidates current.

Stamp mode, Undo and Redo, Focus mode and f-puzzles import support the way you solve.

03 / Keep going

No three-strikes game-over limit

Make a mistake, correct it, and continue. No account is required.

Ads appear only between puzzles, never during one. Rewarded ads for extra answers are optional.

Your next challenge

One daily case. Or one more challenge.

Return for the Daily Case. Test your consistency in Gauntlets. Try Speedruns when you want to race the clock.

Find your next puzzle

The Cryptic reference guide

17 sudoku variants, explained.

Every variant keeps the usual row, column and box rules. Each adds its own constraint or way to reveal the grid.

01
Classic Sudoku
The founding law, and the only one you need today. Every row, every column and every box holds each digit exactly once.
02
Killer Sudoku
Each dotted cage carries a sum. The digits inside must add up to it, and no digit may appear twice within the same cage.
03
Thermo Sudoku
Each thermometer runs from its bulb, the circle, to its tip. The digits must rise strictly along it, every step larger than the last.
04
Diagonal Sudoku
Both main diagonals, corner to corner, must also hold each digit exactly once, just as a row or a column does.
05
Arrow Sudoku
Every arrow has a circle and a path. The digit in the circle must equal the sum of the digits along the path.
06
Knight's Move Sudoku
No two identical digits may sit a chess knight's move apart. The knight moves in an L: two squares one way, then one square at a right angle.
07
Sandwich Sudoku
A clue outside the grid is a sum.
08
German Whisper
On a German Whisper line, any two neighbouring cells must differ by at least 5.
09
Renban Line
The digits on a Renban line form a run of consecutive numbers, in any order you like.
10
Palindrome Line
A palindrome line reads the same in both directions. The first cell matches the last, the second matches the second from last, and so on inwards.
11
Between Lines
The digits on a between line must lie numerically between the two circled endpoints.
12
Region Sum Lines
A region sum line is cut into segments wherever it crosses a box boundary, and every segment must add up to the same total.
13
Kropki Dots
A white dot between two cells means their digits are consecutive, differing by one.
14
XV Pairs
A V between two cells means they sum to 5. An X means they sum to 10.
15
King's Move Sudoku
No two identical digits may sit a chess king's move apart.
16
Fog of War Sudoku
The grid lies under fog. You see only the given digits and the cells beside them.
17
Miracle Sudoku
Three rules at once, and every one is about pairs of cells.

See all variants

The Technique Academy

25 solving techniques, easiest first.

The patterns that crack hard puzzles, one lesson at a time. Each comes with five practice boards.

Easy01
Naked Single
A naked single is a cell with only one digit left that it could possibly hold.
Easy02
Hidden Single
A hidden single is a digit that has only one cell left to live in within a row, column or box.
Medium03
Naked Pair
A naked pair is two cells in one unit that share the same two candidates and nothing else.
Medium04
Hidden Pair
A hidden pair is two digits that, within one unit, can only go in the same two cells.
Medium05
Pointing
Pointing happens when a digit's remaining places in a box all lie along a single row or column.
Medium06
Claiming
Claiming is the mirror image of pointing: a digit's places in a row or column all sit inside one box.
Hard07
Naked Triple
A naked triple is three cells in one unit whose candidates together draw from just three digits.
Hard08
X-Wing
An X-Wing is a digit that appears in exactly two cells in each of two rows, with those cells sharing the same two columns.
Hard09
Swordfish
A Swordfish is an X-Wing with a third arm: a digit confined to two or three cells in each of three rows, all within the same three columns.
Expert10
XY-Wing
An XY-Wing is three cells with two candidates each: a pivot holding X and Y, and two pincers, one holding X and Z and the other Y and Z, each seeing the pivot.
Hard11
Hidden Triple
A hidden triple is three digits that, within one unit, can only go in the same three cells.
Expert12
Naked Quad
A naked quad is four cells in one unit whose candidates come from only four digits between them.
Expert13
Hidden Quad
A hidden quad is four digits that, within one unit, can only go in the same four cells.
Expert14
Skyscraper
A Skyscraper is a digit with exactly two possible cells in each of two rows, where one cell from each row shares a column.
Expert15
2-String Kite
A 2-String Kite links a row and a column that each hold a digit in only two cells.
Expert16
Empty Rectangle
An Empty Rectangle is a box where one digit's candidates lie only along a single row and a single column of that box, leaving an empty rectangle in the rest.
Expert17
XYZ-Wing
An XYZ-Wing is a pivot cell holding three candidates, X, Y and Z, plus two pincers: one holding X and Z, the other Y and Z, each seeing the pivot.
Expert18
W-Wing
A W-Wing is two cells that do not see each other but hold the same two candidates, X and Y, joined by a strong link on X: a unit where X has only two places, one seeing each cell.
Expert19
Finned X-Wing
A finned X-Wing is an X-Wing with a spare candidate, the fin, tucked beside one corner in the same box.
Expert20
Jellyfish
A Jellyfish is the fish family at its largest: a digit confined to the same four columns across four rows, with only two to four places in each row.
Extreme21
BUG+1
BUG+1 arises when every unsolved cell has exactly two candidates except one cell that has three.
Extreme22
Unique Rectangle
A Unique Rectangle is four cells in two rows, two columns and two boxes that could all hold the same pair of digits, which would let you swap them and get a second solution.
Extreme23
Simple Coloring
Simple Coloring follows one digit through a chain of cells linked in pairs, each pair being the only two places for that digit in some unit, and paints alternate cells in two colours.
Extreme24
XY-Chain
An XY-Chain is a run of two-candidate cells in which each neighbour shares a digit with the next, the chain starting and ending on the same digit.
Extreme25
X-Chain
An X-Chain follows one digit along a chain of cells linked alternately by strong links, units where the digit has only two places, and weak links, where it merely cannot be in both.

See all techniques

Before your first puzzle

Who is Professor Cryptic?

Professor Cryptic is the owl who guides you through the app. Hints that show where to look and which technique applies are free. Only the answer itself costs anything. More questions and answers.

Start with a single square

Your next deduction is waiting.

Learn something new. Solve at your own pace.

Get it onGoogle Play Play on the web