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You are looking at a Sudoku board. Your goal is to fill it with digits from 1 to 9. In this stage, you will learn the basic technique of scanning the board. Your task is to find the unique digit for the highlighted cell by focusing on three areas:
Remember the golden rule: each digit can appear only once in a given row, column, and box
We start by scanning the rows. Look at the first row from the top. It already contains some digits, which means:
Treat each of the 9 rows as a separate, closed line in which the digits must remain unique
Now move your attention to the columns. They work exactly like rows, but vertically:
Treat each of the 9 columns as a separate, closed line in which the digits must remain unique
Now for the third area: 3×3 boxes (the bold squares). Each of the 9 boxes follows the same rule:
Often, analyzing a small box is the quickest way to discover a missing digit.
To make things easier, our game automatically colors related cells. When you click any cell, the system highlights in a different color:
Everything highlighted is your area of constraints - this is where you look for uniqueness.
Let's put everything together and fill the first cell in the top-left corner. Look at its highlighted row, column, and box:
Together, we have these digits: 2, 3, 4, 5, 6, 7, 8, 9. So the digit we are looking for is: 1
