Rules:

1. Grid: A 9x9 grid divided into 3x3 subgrids called "regions" or "boxes."
2. Digits: Fill the grid so that each column, each row, and each of the nine 3x3 subgrids contain all of the digits from 1 to 9.

Basic Strategies:

1. Single Possibility (or Naked Single):

   • Look for cells where only one number can fit based on existing numbers in the row, column, and box.

2. Elimination (or Candidate Elimination):

   • Identify numbers that can only go in one place in a row, column, or box due to existing numbers.

3. Subsets (or Naked Pairs/Triples):

   • Identify sets of cells within a row, column, or box that can only contain the same two or three numbers, eliminating those numbers as candidates from other cells in the same unit.

4. Hidden Singles:

   • Search for cells that are the only ones in a row, column, or box that can contain a specific number.

Step-by-Step Solving:

1. Scan the Grid: Start by scanning the grid for obvious numbers that can only go in one cell.

2. Use Elimination: Look for rows, columns, or boxes where a number can only go in one place due to other numbers already present.

3. Apply Subsets: Identify and eliminate candidate numbers in rows, columns, or boxes where specific numbers can only fit in certain cells.

4. Repeat and Check: Continue scanning and applying strategies until you fill the grid.

Tips:

• Practice: Regular practice improves pattern recognition and speed.
• Patience: Sudoku requires logical thinking and may take time to master.

By combining these strategies and practicing regularly, you'll improve your ability to solve Sudoku puzzles efficiently.