🧩 Classic Sudoku Puzzle
Challenge your logic and numerical skills in Classic Sudoku Puzzle! Played on a traditional 9x9 grid, your goal is to logically place numbers 1 through 9 into empty cells across the board. Select from multiple difficulty settings to match your skill level, whether you want a light brain warm-up or an intense mental workout. Use helpful tools like pencil notes to track potential candidates and avoid making costly mistakes as you complete the grid.

🌟 Key Features:
    🔢 Classic 9x9 Grid Layout: Enjoy authentic Sudoku gameplay divided into 3x3 sub-grids for structured logical solving.
    📊 Multiple Difficulty Levels: Choose from easy to expert puzzles tailored for casual solvers and Sudoku veterans alike.
    📝 Interactive Notes Mode: Pencil in candidate numbers within empty cells to map out possibilities and plan complex moves.
    🧠 Brain-Training & Logic: Enhance focus, pattern recognition, and analytical thinking with every completed puzzle.
    ⚠️ Error Tracking: Stay alert to avoid placing duplicate numbers and complete the grid cleanly.

🎮 How to Play & Controls:

    🎯 Objective: Fill all 81 cells so that every row, column, and 3x3 sub-grid contains the digits 1 through 9 without duplicates.

    💡 Solving Rules & Tips:
        • Grid Rule: Ensure no number repeats within the same row, column, or 3x3 box.
        • Use Notes: Click the "Notes" button to toggle note-taking mode and jot down candidate digits in empty cells.
        • Avoid Mistakes: Double-check intersecting rows and columns before committing to a final digit placement.

    👆 Controls:
        • Desktop: Left-click an empty cell to select it, then click your desired number from the keypad (or press corresponding number keys on your keyboard).
        • Mobile: Tap an empty cell to highlight it, then tap a number on the on-screen keypad to place it or enter a note.