NRC Sudoku Solver

An interactive web application that helps you solve NRC Sudoku puzzles from NRC Handelsblad.

What is NRC Sudoku?

NRC Sudoku is a challenging variant of the classic Sudoku puzzle, originally published by the Dutch newspaper NRC Handelsblad. It features additional constraints that make it more complex and engaging than standard Sudoku.

Rules of the Game

NRC Sudoku follows the basic Sudoku rules with an important twist:

1. Standard Rules:

   • Fill a 9×9 grid with digits from 1 to 9
   • Each row must contain all digits 1-9 without repetition
   • Each column must contain all digits 1-9 without repetition
   • Each of the nine 3×3 boxes must contain all digits 1-9 without repetition

2. NRC Special Rules:

   • In addition to the nine standard 3×3 boxes, there are four extra 3×3 regions (highlighted in gray)
   • These four additional regions are positioned at:
     • Top-left corner starting at row 2, column 2 (using 1-indexed coordinates)
     • Top-right corner starting at row 2, column 6
     • Bottom-left corner starting at row 6, column 2
     • Bottom-right corner starting at row 6, column 6
   • Each of these four gray regions must also contain all digits 1-9 without repetition

This means NRC Sudoku has 13 regions in total (9 standard boxes + 4 NRC boxes) that must satisfy the uniqueness constraint, making it significantly more challenging than regular Sudoku!

Learn more and play online: https://www.nrc.nl/puzzels/sudoku

Features

• 🎯 Interactive 9×9 Sudoku grid with visual distinction for NRC regions (gray boxes)
• ⌨️ Keyboard navigation using arrow keys
• 🔢 Easy number input
• 🤖 Automatic solver using logical deduction algorithms
• 📱 Responsive design that works on desktop and mobile devices

How to Use

1. Input your puzzle: Click on any cell and type a number (1-9) to fill in the initial puzzle clues
2. Navigate: Use arrow keys to move between cells, or click directly on any cell
3. Clear a cell: Press Backspace to remove a number
4. Solve: Click the "Solve" button to automatically solve the puzzle using logical deduction
5. Watch it solve: The solver fills in cells step-by-step, allowing you to see the solution process

Development

This project is built with:

• SvelteKit - The web framework
• TypeScript - Type safety
• Tailwind CSS - Styling
• Vite - Build tool

Getting Started

Install dependencies:

npm install

Start the development server:

npm run dev

Build for production:

npm run build

Preview the production build:

npm run preview

Type checking:

npm run check

License

This project is open source and available for educational purposes.