Sudoku hardly needs introducing, and this version keeps to the classic rules without adding anything unusual: a nine-by-nine grid, nine boxes, and every row, column and box holding the digits one to nine exactly once. No arithmetic is involved despite the numbers - they are simply nine symbols that are easy to tell apart, and the puzzle is pure deduction. Difficulty is selectable, which matters more here than in most puzzles. An easy grid can be finished by scanning alone, filling in squares wherever only one digit will fit. Harder grids remove that possibility on purpose and push you towards reasoning about what a digit cannot be rather than what it is. Every puzzle has exactly one solution and can be reached without guessing, so if you find yourself picking a number at random there is a deduction still sitting somewhere on the board. Sessions can be as short or as long as you like, and the grid holds its state while you think.
How to Play Sudoku
Click or tap an empty cell to select it, then choose a digit from one to nine to place it. Use the notes or pencil mode to record which digits are still possible in a cell - on medium and hard grids this is essential rather than optional. Pick a difficulty level before you begin.
Tips and Tricks
Scan by digit, not by cell. Take the number one, look at every row, column and box it already occupies, and see where it is forced. Then move on to two. This finds far more than staring at empty squares does.
Fill in your pencil marks before the grid gets hard. Most people who stall on a medium puzzle stalled because they skipped notes and can no longer see which candidates remain.
If two cells in a box can only hold the same two digits, no other cell in that box can hold either of them. That single rule unlocks most medium grids on its own.
Never guess. Every puzzle here has one solution reachable by logic, so a guess that looks right will usually collapse twenty squares later with no way to trace the error.
Frequently Asked Questions
Do I need to be good at maths?
No. The digits are just nine different symbols and nothing is added or multiplied. Sudoku is a logic puzzle that happens to use numbers because they are quick to distinguish.
Which difficulty should I start on?
Easy, unless you already play regularly. Easy grids can be finished by scanning alone, which teaches the basic technique before the harder levels start demanding candidate notes.
Can a puzzle have more than one answer?
No. Every grid is generated with exactly one solution, and that solution can always be reached by deduction without guessing at any stage.
What should I do when I am completely stuck?
Go back and complete the pencil marks across the whole grid. Being stuck almost always means a forced digit or a pair is sitting there unnoticed, rather than the puzzle being unfair.
Does it work on a phone?
Yes. Sudoku runs in the browser on GN Math and the grid scales to touchscreens, though a larger screen is easier when you are reading candidate notes.
Tags
sudoku, logic puzzle, number puzzle, brain game, classic sudoku, deduction game, puzzle game, single player, browser game, no download
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