About Sudoku

What is Sudoku?

Sudoku is a logic-based number placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 subgrids contains all of the digits from 1 to 9.

Features

• Three difficulty levels: Easy, Medium, and Hard
• Intelligent puzzle generation with unique solutions
• Real-time conflict detection
• Pencil marks (notes) for candidate tracking
• Auto-notes feature to fill in all candidates
• Undo functionality with full move history
• Hint system for when you get stuck
• PDF export for offline play
• Move counter and timer
• Mobile-friendly responsive design

How to Play

1. Select a cell by clicking or tapping on it
2. Enter a number using the number pad or keyboard (1-9)
3. Use arrow keys to navigate between cells
4. Toggle Notes mode to add pencil marks
5. Use the Undo button to reverse mistakes
6. Click Check to verify your solution

Technology

Built with Next.js, React, TypeScript, and Tailwind CSS. The puzzle generation uses a backtracking algorithm to create valid Sudoku grids with unique solutions.