# Different versions of Sudoku

## Sudoku 9×9

Sudoku is a logic-based puzzle that is very popular all around the world.
The goal is to fill the 9×9 grid with digits in such a way that each row and each column contains all the digits from 1 to 9, but each digit can only appear once.
The smaller subgrids containing 9 squares also must be completed in such a way that they only contain each digit once.

## Sudoku 4×4

It is an easier version of the traditional Sudoku.
The basic rules of the game are the same, but you have to find the correct digits in a significantly smaller grid with fewer squares.
The game is played in a 4×4 grid consisting of 4 2×2 subgrids that you have to fill with digits from 1 to 4.
It is the most suitable version for those who are new to the game, and it could also be the ideal choice for children.

## Sudoku 16×16 (mega sudoku)

It is a much more difficult version of the traditional Sudoku. The basic rules of the game are the same as in the traditional version of Sudoku, but considering the fact that the game is played in a 16×16 grid that consists of 16 4×4 subgrids, it is much harder and it takes longer to solve the puzzle, than in the original version. In this version you have to fill each row and column with digits from 1 to 16, and there are also different versions where you have to use letters from A to G instead of the digits from 10 to 16. It is the most suitable choice for those who feel like they can easily solve even the most difficult 9×9 boards.

## Killer sudoku

The goal is to fill the board with digits from 1 to 9, while following these rules: every row, column and subgrid can contain each digit (from 1 to 9) only once, and the sum of all digits in a cage must match the small number in the corner of the cage. None of the digits can appear more than once in a cage (this is the basic rule of Killer Sudoku, which means that none of the cages can consist of more than 9 squares).

## Hypersudoku

Hyper Sudoku is one of the most popular versions of the original Sudoku. It also appears in magazines and newspapers all around the world. In this version the board looks almost the same as in the original version of the game, with the exception that there are additional boxes containing 9 squares within the grid, that also have to be filled with the digits from 1 to 9. As a result the process of solving the puzzle is slightly different than in the original version, since you have to pay attention to the overlapping boxes as well. The overlapping boxes give more information to the players, which can reduce the number of possibilities in the remaining squares, and it also makes it easier to solve the puzzle. But at the same time you have to pay attention to several subgrids, which makes it harder to find the solution. The approach is similar to that of the original Sudoku, but you have to concentrate more on the subgrids and on understanding the overlapping boxes, rather than on the rows and columns.

The sudoku was introduced in Japan by Nikoli in the paper Monthly Nikolist in April 1984.