Sudoku

Sudoku puzzle game with easy to hard grids
English
Sudoku is built on a single, elegant idea: place the digits 1 through 9 in a 9x9 grid so that no digit repeats in any row, column, or 3x3 box. From that one constraint flows an entire world of deduction. A well-made Sudoku never asks you to guess - every grid can be solved step by step through logic alone, and each move you prove correct unlocks the next. That is what makes the puzzle so satisfying: the moment a stubborn cell finally reveals its only possible digit feels earned, not lucky. This version of Sudoku brings that experience to your screen with 400 unique puzzles spread across four difficulty levels, from gentle grids for learning the basics to sparse expert layouts that demand your full attention. Pencil marks, error checking, and a timer are there when you want them, and stay out of the way when you don't.

How to Play Sudoku

The rules of Sudoku fit in a few lines, which is exactly why the puzzle is so approachable:
  • Fill the 9x9 grid so that every cell contains a digit from 1 to 9
  • Each row must contain all nine digits with no repetition
  • Each column must contain all nine digits with no repetition
  • Each of the nine 3x3 boxes must contain all nine digits with no repetition
  • Some cells are already filled in - these clues are fixed and cannot be changed
  • No arithmetic is involved: you never add or multiply anything, you only reason about where each digit can and cannot go
The digits are just convenient symbols. The same puzzle would work with letters or colors, because Sudoku is a game of pure placement logic.

Difficulty Levels

Every puzzle in the game belongs to one of four difficulty levels, defined by the number of clues you start with. Fewer clues mean more empty cells to deduce and deeper chains of reasoning:
  • Easy - 50 clues. Most of the grid is already filled in, so single candidates appear quickly. Ideal for learning the rules and building confidence.
  • Medium - 40 clues. You will need to scan rows, columns, and boxes more systematically, and pencil marks start to become useful.
  • Hard - 30 clues. These grids reward careful candidate tracking and intermediate techniques such as naked pairs.
  • Inhuman - 20 clues. Sparse grids with long deduction chains, built for solvers who want a serious challenge.
Each level contains 100 hand-crafted puzzles, and the Hard and Inhuman levels draw on expert 17-clue puzzle patterns - layouts related to the theoretical minimum number of clues a 9x9 Sudoku can have.

Features

  • 4 difficulty levels - Easy (50 clues), Medium (40 clues), Hard (30 clues), and Inhuman (20 clues)
  • 400 unique puzzles - 100 hand-crafted grids per difficulty level, enough for a long time before anything repeats
  • Professional puzzle construction - Hard and Inhuman levels use expert 17-clue puzzle patterns
  • Smart hints system - get help in the form of pencil marks that guide your solving without simply handing you the answer
  • Error detection - the clear errors feature lets you instantly spot and remove mistakes so one wrong digit never silently ruins a whole grid
  • Time tracking - the game records your solving time so you can measure progress and try to beat your personal best on each level
  • 47 languages supported - play in your preferred language

Solving Techniques

Sudoku technique is a ladder: each rung uses the same rules, applied with a little more structure. Here are the methods that carry you from Easy to Inhuman, roughly in order of difficulty:
  • Scanning - run along the rows and columns that already contain a given digit and cross off the cells it can no longer occupy. Where a digit is excluded from every cell of a box except one, it must go there. Scanning alone solves much of an easy grid.
  • Naked single - a cell where, after eliminating everything already present in its row, column, and box, only one candidate digit remains. Whatever that digit is, it must be placed there.
  • Hidden single - the mirror image: a digit that can only fit in one cell of a row, column, or box, even though that cell still has other candidates. The digit's uniqueness in the unit, not the cell's, forces the placement.
  • Pencil marks - from Medium difficulty upward, write the remaining candidates in each empty cell instead of keeping them in your head. Most advanced techniques are really patterns you spot in your pencil marks; the game's hint system builds on exactly this idea.
  • Naked pair - when two cells in the same row, column, or box contain exactly the same two candidates, those two digits are locked into those two cells. You can erase them from every other cell in that unit, which often cracks a position wide open.
  • X-Wing - an expert technique: when a candidate digit is restricted to the same two columns in each of two different rows, forming a rectangle, that digit can be eliminated from those two columns everywhere outside the rectangle. Look for it on Inhuman grids when simpler methods stall.
A good habit at any level: after every digit you place, ask what it newly forbids. Each placement removes candidates from up to twenty other cells, and the next deduction is usually hiding among them.

Did You Know?

  • Modern Sudoku descends from "Number Place", a puzzle published in the United States in 1979 and credited to Howard Garns, a retired architect.
  • The puzzle became a phenomenon in Japan in the 1980s, where the publisher Nikoli popularized it under the name Sudoku - roughly "the digits must be single" - before it spread back around the world.
  • A 9x9 Sudoku needs at least 17 clues to have a unique solution. No 16-clue puzzle with a single solution exists - a result proved in 2012 by an exhaustive computer search.
Whether you have five minutes for an Easy grid or a whole evening to wrestle with an Inhuman one, the ritual is the same: scan, deduce, place, repeat. Start with Easy mode to internalize the rules, let pencil marks carry you through Medium and Hard, and see how far up the ladder of techniques you can climb.

Frequently Asked Questions

Does every Sudoku puzzle have a unique solution?

A properly constructed Sudoku has exactly one solution, and that is part of what makes it solvable by logic alone. All 400 puzzles in this game are built that way, so you never have to guess between two valid endings.

Do I need to be good at math to play Sudoku?

No. Sudoku involves no arithmetic at all - you never add, subtract, or calculate anything. The digits 1 to 9 are just nine distinct symbols, and the whole game is about deducing where each one can and cannot go.

What does the 17-clue minimum mean?

It is a mathematical result, proved in 2012, showing that a 9x9 Sudoku must start with at least 17 clues to have a unique solution; no valid 16-clue puzzle exists. The Hard and Inhuman levels in this game use expert puzzle patterns derived from such minimal 17-clue layouts.

Can I play Sudoku offline?

Yes. Once the game is loaded, the puzzles work without an internet connection, so you can keep solving on a plane, on the subway, or anywhere else offline.

What happens if I make a mistake?

The game includes an error detection feature: the clear errors option instantly highlights and removes incorrect digits. That way a single wrong placement never silently corrupts the rest of your grid.

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