Quick sudoku on paper – Taras Sidorov

A Sudoku puzzle is defined as a logic-based, number-placement puzzle. The objective is to fill a 9×9 grid with digits in such a way that each column, each row, and each of the nine 3×3 grids that make up the larger 9×9 grid contains all of the digits from 1 to 9.
This application is a sudoku game on paper in two versions: complex and simple.