Sudoku
A clean screen, no-guess puzzles and a new sudoku every day.
How to play
Each row, each column and each 3×3 box of the 9×9 grid holds every digit from 1 to 9 exactly once. Tap a cell, then tap a digit; tapping the same digit again erases it. Use the pencil to write small candidates where you are unsure: when a digit is placed, matching notes in its row, column and box disappear automatically. If you get stuck, Hint shows the next step and the technique that finds it, and a second tap places the digit. There is no mistake limit; your time and points are tracked and unfinished puzzles are saved.
How to play Sudoku: a detailed guide
Sudoku is a logic puzzle in which you fill a 9×9 grid with the digits 1 to 9. The rule fits in one sentence: every row, every column and every 3×3 box contains each digit exactly once. Sudoku on CetinsGame comes with a clean screen: no story, no clutter, just the grid, the digit keys and four tools. Every puzzle has exactly one solution, and none of them ever needs guessing.
This guide covers the rules, the controls, which techniques each of the four levels asks for, the Daily Sudoku, hints and points, and solving methods from easy to expert. If you would rather start on a smaller grid, the 6×6 Mini Sudoku is inside the game too.
Goal and rules
The grid has 9 rows and 9 columns, and thick lines divide it into nine 3×3 boxes. Your goal is to fill every empty cell:
- Each row contains every digit from 1 to 9 once.
- Each column contains every digit from 1 to 9 once.
- Each box contains every digit from 1 to 9 once.
The bold given digits cannot change. The givens are laid out with 180° rotational symmetry: turn the grid upside down and the pattern of filled cells stays the same. There is no mistake limit and no way to lose; the timer runs while you play. An unfinished puzzle is saved, and Continue in the level list takes you back to where you stopped.
Controls and options
- Placing a digit: tap a cell, then tap a digit key. Tapping the same digit again erases it. Each key shows how many of that digit are still missing.
- Notes: turn the pencil on to write small candidate digits in a cell. When a digit is placed, matching notes in its row, column and box are removed automatically.
- Digit lock: long-press a digit, then every cell you tap gets that digit.
- Undo is unlimited; Erase clears the selected cell.
On a keyboard: 1-9 digit, arrow keys move, N notes, Z undo, H hint, Backspace erase, Esc pause. Pausing hides the grid and stops the timer. Note all candidates in the pause menu writes every possible digit into every empty cell with one tap.
Options has four settings: Show mistakes (on: wrong digits turn red; off: only rule conflicts such as two 5s in one row are shown), Auto-remove notes, Row and column highlight and Highlight matching digits. For the theme you can choose Plain, Tile in the colours of Iznik tiles, or the dark Night.
Levels: difficulty measured by technique
The game's solver works through every puzzle the way a person would, starting with the easiest technique; the level is set by the hardest technique the puzzle needs. Puzzles at each level cannot be solved with the techniques of the level below, so a Medium puzzle really is harder than an Easy one.
| Level | Techniques needed | Givens (approx.) |
|---|---|---|
| Easy | Naked single, Hidden single | 36-42 |
| Medium | Locked candidates, Naked pair | 29-35 |
| Hard | Hidden pair, Naked triple, Hidden triple | 25-32 |
| Expert | X-Wing, XY-Wing, Swordfish or XYZ-Wing | 22-32 |
No level ever needs trial and error, and every puzzle has been checked by computer to have a single solution. Each level has 500 puzzles; once you finish them all, the pool starts again with the digits swapped around.
Daily Sudoku, streaks and the archive
The Daily Sudoku changes every day at midnight Turkey time, and everyone gets the same puzzle. The difficulty follows the week: Monday Easy, Tuesday and Wednesday Medium, Thursday and Friday Hard, Saturday Medium, Sunday Expert.
Days you solve in a row build your streak. You can play missed days from the Archive, but archive solves do not count toward your streak and score half points. When you finish, a heading such as N players solved it today shows how solve times were spread out, along with a countdown to the next puzzle.
Hints, points and records
A Hint makes you think first: the first tap shows the next step and the technique that finds it, for example 'Hidden single: in this box, 5 can only go in the marked cell'. For harder techniques, the cells that eliminate candidates are shaded. A second tap places the digit. If the grid has wrong digits, the hint points those out first. Each puzzle comes with 3 free hints; when they run out you can choose to watch a short ad for 3 more. In the Daily Sudoku every hint adds 30 seconds to your time.
Points are the level base (Easy 1000, Medium 2000, Hard 4000, Expert 8000) times a speed multiplier between 0.5 and 2, based on a target time: Easy 7, Medium 14, Hard 25, Expert 40 minutes. Finish on target and the multiplier is 1; finish in half the time and it is 2. Each hint takes off 10% and each mistake 5%, but the deduction never goes beyond 80%. Points add up, and the leaderboard shows your Total points. Statistics keep your average time per level and your best time on solves without hints; beat it and you see New record!
Strategy: from singles to X-Wing
- Hidden single: pick a digit and look at where it can go in each box. If only one cell is left, the digit goes there.
- Naked single: if a cell's row, column and box rule out eight digits, the remaining one goes in.
- Locked candidates: if a digit's candidates inside a box all sit in one row, remove that digit from the rest of that row outside the box.
- Naked pair: if two cells in a unit have only 2 and 7 as candidates, those two digits belong to them and can be removed from the other cells. Triples are the same idea with three cells.
- X-Wing: if a digit can go in only the same two columns in two rows, remove it from the other cells of those columns. Swordfish builds the same idea with three rows.
Tips
- Start with Easy: get comfortable with naked and hidden singles, because every higher level is built on them.
- With Highlight matching digits on, tap a digit; the boxes still missing it stand out at a glance.
- Watch the counts on the keys: finding the spot for a digit with only one left is often the easiest move.
- If you are placing the same digit in many cells, use the digit lock: long-press the digit, then tap the cells.
- When you get stuck on Hard or Expert, start with Note all candidates; the notes clean themselves up as digits go in.
- On the first hint tap, read only the explanation and try to find the digit yourself before the second tap.
- In the Daily Sudoku each hint adds 30 seconds; to keep your streak, solve it on the day.
Sudoku: from Latin squares to the newspaper page
Sudoku is a logic puzzle rooted in the Latin squares that mathematicians studied in the 18th century. Its modern 9×9 form with boxes first appeared in a US puzzle magazine in 1979, got the name "sudoku" in Japan in 1984 and spread to newspapers all over the world in the mid-2000s. The digits are only symbols: there is no arithmetic, just logic. The Tile theme takes its cobalt, turquoise and red from İznik tiles.
- First form
- 1979, United States; called Number Place
- The name Sudoku
- 1984, Japan; short for 'the digits must be single'
- Worldwide spread
- End of 2004, through a British newspaper
- Ancestor
- The Latin square, studied by 18th-century mathematicians
- Valid grids
- About 6.67 × 10²¹
- Fewest clues
- 17 (shown by a computer search in 2012)
Latin squares
Sudoku's mathematical ancestor is the Latin square: n symbols placed in an n×n table so that each appears once in every row and every column. Mathematicians studied these squares in the 18th century and asked how they could be built. Every completed sudoku grid is in fact a Latin square; sudoku adds one more rule: each of the nine boxes must also contain every digit once.
From Number Place to Sudoku
The boxed 9×9 puzzle we know today appeared in 1979 in a puzzle magazine in the United States under the name Number Place. In 1984 a puzzle publisher in Japan introduced it there and gave it the name Sudoku, a shortening of a longer Japanese phrase meaning 'the digits must be single'. The digits are not used for arithmetic: they are just nine different symbols, and the same puzzle could be built with letters or colours.
Going global
Sudoku spread around the world after a British newspaper began publishing it at the end of 2004. In 2005 it reached the puzzle pages of newspapers in many countries, then moved on to books, computers and phones. That is also why the name barely changes from language to language: the puzzle travelled the world under its Japanese name, and many languages took it over without translating it.
Sudoku by the numbers
The number of completely filled 9×9 grids that follow the rules is about 6.67 × 10²¹, more than six sextillion. People also wondered for a long time how few givens a puzzle with a single solution could have. In 2012 a large computer search showed that no 16-clue sudoku has a unique solution, so at least 17 clues are needed.
In our game: the Tile theme
The Tile theme of Sudoku on CetinsGame takes its colours from Iznik tiles, the glazed ceramic tiles of the Turkish town of Iznik: cobalt blue, turquoise and tile red, a glazed white background and a tiled border around the grid. Iznik tile making reached its finest period in the 16th century. The game's calm music and sound effects are original sounds generated in code.
How Sudoku was made
Sudoku is one of the games people search for by name, in every language, every day. So the starting point was not to invent a new rule but to present a well-known game as cleanly as possible: a sudoku that opens without signing up, is never interrupted by ads while you play, and shows nothing on screen but the grid and the digits. A story was left out on purpose; someone who wants to play sudoku should see the grid right away.
Most of the work went into the difficulty names. In many sudokus, "hard" only means fewer digits. Here every puzzle went through a solver that thinks like a person: at each step it tries the easiest technique and records which technique the puzzle needs. Easy is solved with singles alone, Medium with locked candidates and pairs, Hard with hidden pairs and triples, Expert with X-Wing, XY-Wing or Swordfish. A puzzle at each level cannot be finished with the techniques of the level below, so the level name really means something. No puzzle needs guessing, and each one was also checked by counting to have exactly one solution.
The hint grew out of the same solver. Simply handing a stuck player the digit teaches nothing, so the hint first shows, with shaded cells, which technique works and where, and places the digit only on the second tap. Someone who starts on Easy can follow the hints all the way up to Expert techniques.
The Daily Sudoku gives everyone the same puzzle each day, with difficulty spread over the week: easy on Monday, expert on Sunday. The 6×6 Mini Sudoku was made for children and classrooms: the same rules, fewer digits, bigger cells. The Tile theme takes its cobalt, turquoise and red from İznik tiles, and the calm background music was generated in code from a scale close to the Uşşak makam. The game launched as version 1.0 on 14 October 2026 and is played in seven languages.
Frequently asked questions
Do you ever have to guess in Sudoku?
No. Every puzzle in the game has been run through a solver and can be finished with logical steps alone. If you are stuck, you are missing a technique; the Hint shows the next step and names the technique.
How are the levels decided?
Not by the number of givens but by the hardest technique the solution needs. Easy uses singles, Medium locked candidates and naked pairs, Hard hidden pairs and triples, and Expert X-Wing, XY-Wing, Swordfish or XYZ-Wing.
Why should a sudoku have only one solution?
A single solution means every digit can be found by logic; with two solutions you would have to guess somewhere. Every puzzle in the game has been checked by computer to have exactly one solution.
Does the game end if I make a mistake?
No, there is no mistake limit. With Show mistakes on, wrong digits turn red; with it off, only rule conflicts are shown. Each mistake takes 5% off your points but never stops you finishing.
When does the Daily Sudoku change?
Every day at midnight Turkey time. Everyone solves the same puzzle, and the difficulty climbs through the week from Easy on Monday to Expert on Sunday.
Do archive puzzles count toward my streak?
No. The archive lets you play days you missed, but your streak only grows with puzzles solved on their own day. An archive solve scores half points.
What is an X-Wing?
If a digit can go in only the same two columns in two different rows, it must take those two columns in those rows. So it can be removed from every other cell in those columns. Swordfish is the same idea with three rows.
How are points calculated?
The level base (Easy 1000, Medium 2000, Hard 4000, Expert 8000) is multiplied by a speed multiplier between 0.5 and 2. Each hint takes off 10% and each mistake 5%; your points add up on the leaderboard.
What happens when I run out of hints?
Each puzzle comes with 3 free hints. After that you can choose to watch a short ad for 3 more, or simply keep going without hints.
Is Sudoku free?
Yes. No download or account needed; it plays right in your browser. Watching an ad for a hint is always your choice.
Will I lose my progress?
Your progress is saved automatically on this device. Sign in and it moves to your account, so you can continue on any device.
Can I play on my phone?
Yes. The game opens full screen on phones; tap the X in the corner to exit. On iPhone use "Add to Home Screen" to play it like an app.
Can I play Sudoku offline?
Yes. A game you have opened once is stored on your phone or computer and opens without internet. Leaderboards and cloud saves need a connection.
Which languages are available?
Turkish, English, Spanish, Portuguese, German, French and Russian.
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