The Complete Guide to Sudoku

Chapter 1: What Is Sudoku and Why People Love It

Let's start with what a Sudoku puzzle actually is, because if you've only ever glimpsed one over someone's shoulder, it might look like homework: a 9-by-9 grid, 81 little squares, some of them already filled in with numbers from 1 to 9. That's it. The puzzle gives you a handful of these numbers as clues, and your job is to fill in the rest of the empty squares so that every row, every column, and every 3-by-3 box contains the numbers 1 through 9 exactly once.

That's not just the goal - that's literally the entire rule set. There are no other rules. No math skills are involved beyond knowing that 1, 2, 3, 4, 5, 6, 7, 8, and 9 are different from each other. You are never adding, subtracting, multiplying, or dividing. You're not calculating anything. You're placing numbers according to a simple logic puzzle, kind of like a cross between chess and a seating chart.

So what does a session actually look like? Imagine this: it's a rainy Tuesday evening, you've got a cup of tea cooling beside you, and you open a puzzle that claims to be "easy." The grid is maybe 20 percent pre-filled. You start with a row that has eight numbers in it already. Since every row needs 1 to 9 exactly once, the missing number is obvious - it's the one digit not already present. You write it in, and that tiny