# Sudoku: Rules and Basics

# How to Play Sudoku:

## Step 1. Use Numbers 1-9

Sudoku games are played on a 9 x 9 grid. There are 9 "squares" (consisting of 3 x 3 spaces) in rows and columns. Each row, column and square (9 spaces each) needs to be filled with numbers 1-9, and no numbers are repeated in the row, column or square. Does it sound complicated? As you can see from the actual Sudoku grid below, each Sudoku grid has filled some space. The more space is filled, the easier the game is-the more difficult the Sudoku puzzle, the less space has been filled.

## Step 2. Don’t Repeat Any Numbers

As you can see, in the square (blue circle) in the upper left corner, the square has been filled with 7 of the 9 spaces. The only missing numbers in the square are 5 and 6. By looking at the missing numbers, rows or columns in each square, we can use the process of elimination and deductive reasoning to determine which numbers need to be entered in each blank.

For example, in the square in the upper left corner, we know that we need to add 5 and 6 to complete the square, but based on the adjacent rows and squares, we cannot clearly deduce which number to add in which space. This means that we should now ignore the square in the upper left corner and try to fill in spaces in some other areas of the grid.

## Step 3. Don’t Guess

Sudoku is a game of logical reasoning, so you don't have to guess. If you don’t know what number to place in a particular space, continue scanning other areas of the grid until you find an opportunity to place a number. But don't try to "impose" anything – Sudoku rewards patience, insight, and recognition of the pattern, not blind luck or guesswork.

## Step 4. Use Process of Elimination

What does it mean to play Sudoku with "destroy process"? This is an example. In this Sudoku grid (shown below), the leftmost vertical column (blue circle) is only missing a few numbers: 1, 5, and 6. One way to figure out what numbers can be in each space is to use the "elimination process" by checking whether there are other numbers in each square-because each square cannot have 1-9 numbers repeated (or Row or column).

In this case, we can quickly notice that the number 1 is already in the upper-left and middle-left squares of the grid (number 1 is circled in red). This means that there is only one space left in the leftmost column, a 1 may appear, and it is circled in a green circle. This is how the elimination process in Sudoku works-you find out which spaces are available and which numbers are missing-and then you infer which numbers fit each space based on where those numbers are in the grid.

The rules of Sudoku are relatively simple, but the game is ever-changing, with millions of possible number combinations and multiple difficulty levels. But this is all based on the following simple principles: use numbers 1-9, fill in the blanks based on deductive reasoning, and do not repeat any numbers in each square, row or column.