Sudoku Classic is a free puzzle game available on Android that challenges your brain and helps you relax at the same time. With a 9x9 grid, you need to fill in the numbers 1-9 without repeating any numbers within the row, column, or square. The game is designed to exercise your brainpower, build mind resiliency and improve your short-term memory.

The game offers 4 difficulty levels: Easy, Medium, Hard, and Evil, making it suitable for players of all skill levels. It also features Killer Sudoku, a mix of Sudoku and Kakuro, which adds an extra layer of challenge for experienced players.

In addition to the standard gameplay, Sudoku Classic also includes daily challenges that allow you to earn special trophies. The game also includes several helpful features such as Undo, Erase, Pencil, Fast Pencil, and Hint, which help you solve puzzles faster.

If you're looking for a fun and challenging puzzle game to exercise your brain and relax, Sudoku Classic: Number Puzzle is definitely worth checking out.