Sudoku for beginners

This is a simple Sudoku with focus on the game: - no ads, - no timer, - no sounds, - no fancy distracting stuff, - simply enjoy the game It packs some features that are useful for beginners: - several difficulty levels - easiest level has a hint button (press it when you're stuck) - colors for the numbers - remaining numbers indicator - note taking mode - unlimited undo levels - rules of the game are explain