Rules of Sudoku
Learn how to play before you start solving puzzles.
Objective
The goal of Sudoku is to fill every empty cell in the grid with a number so that each column, each row, and each sub-grid (box) contains all of the numbers from 1 to N, where N is the size of the grid (9 for a standard game, 6 for easy mode).
How to Play
- The puzzle starts with some cells already filled in. These are called given numbers and cannot be changed.
- Each row must contain every number from 1 to N exactly once. No duplicates are allowed in any row.
- Each column must contain every number from 1 to N exactly once. No duplicates are allowed in any column.
- Each sub-grid (the thicker-bordered boxes) must also contain every number from 1 to N exactly once.
- Use logic and deduction to determine which number belongs in each empty cell. There is only one valid solution for each puzzle.
Grid Sizes
Easy Mode (6x6)
A 6x6 grid divided into six 2x3 sub-grids. Each row, column, and sub-grid must contain the numbers 1 through 6. Great for beginners.
Hard Mode (9x9)
The classic 9x9 grid divided into nine 3x3 sub-grids. Each row, column, and sub-grid must contain the numbers 1 through 9. The standard challenge.
Tips for Beginners
- Start by scanning rows, columns, and boxes for numbers that appear frequently.
- Look for cells where only one number is possible — these are called naked singles.
- Use pencil marks (mental notes) to track candidate numbers for each cell.
- Work systematically and avoid guessing. Every puzzle can be solved through logic alone.
Credits
Sudoku Master was created as a project for CS5610 Web Development.