Comfortable Sudoku

## Description

Comfortable Sudoku is a easy-to-use and intuitive interface Sudoku.

Sudoku is a logic-based,number-placement puzzle. The objective is to fill empty grid with digits so that each column, each row, and each of the nine 3×3 block that compose the grid contains all of the digits from 1 to 9.

Comfortable sudoku features:
-Press and hold a grid, you can enter a number directly.
-10 different levels of difficulty
-Three input modes
-Undo / Redo
-Hint mode