¹The rules of Sudoku are simplicity itself. But, in order to better understand them, and the solving techniques we'll discuss later, it's best to start with the Sudoku board itself, and all of its components.

²The Board is everything you see to the left (the 9x9 grid.)

³The next biggest segment is the Band. There are three horizontal Bands and three vertical Bands. Let's highlight Horizontal Band 1. If you look at just the bold lines on the Board you can picture it as a Tic-Tac-Toe board. In that analogy, a Sudoku Horizontal Band would be a row on a Tic-Tac-Toe board, and a Sudoku Vertical Band would be a column on a Tic-Tac-Toe board.

⁴Sticking with this analogy, our next largest Sudoku segment: the Block would be a Tic-Tac-Toe square. Blocks are numbered from left to right, top to bottom, as follows:

• Block 1.
• Block 2.
• Block 3.
• Block 4.
• Block 5.
• Block 6.
• Block 7.
• Block 8.
• Block 9.

⁵Abandoning the Tic-Tac-Toe analogy, we come to the next largest Sudoku segment: the Lane. A Lane is an umbrella term for a Row or a Column.

⁶A Row is a horizontal Lane, stretching from the left to the right side of the board. People refer to rows in different ways, but in Sue we will always refer to them as Row 1 through Row 9.

⁷A Column is a vertical Lane, stretching from the top to the bottom of the board. People refer to columns in different ways, but in Sue we will always refer to them with letters, as Column A through Column I.

⁸This brings us to the next segment: the Cell. A Cell occurs at the intersection of a Row and Column, and is referred to by the Column/Row names (as in a spreadsheet). Here we highlight Cell A1. And here is Cell I9. There are 81 Cells in all on the Board, all of which must be filled in with a Big Number for the puzzle to be solved.

⁹This brings us to the lowest level segment of the Board: the Candidate or "little number." Each Cell can contain up to 9 Candidates (potential Big Numbers.) These are placed in the cell (as small numbers) from left to right, top to bottom (the same as we number the Blocks.) Here, we display all possible Candidates in all Cells on a blank Board.

¹⁰Now that you understand all of the above, we can present to you:

¹¹All the Rules of Sudoku in one sentence!
Each Block and each Lane must contain all of the numbers 1-9.

¹²Implicit in the above single rule of Sudoku is the fact that no number can repeat within a Block or a Lane, and no number can be skipped. So the numbers 1-9 must appear exactly once in each Block and in each Lane. Here is an example, from a fully solved puzzle.

¹³To start you off, each Sudoku puzzle gives you at least 17 cells where the correct number has already been filled in for you. These, appropriately enough, are called the "Givens." (In Sue, Givens are shown in black, while Big Numbers that you enter are shown in blue.) Based just on these Givens, using the process of elimination and pattern recognition, you should be able to deduce the correct numbers to fill in for all of the remaining blank Cells*.

¹⁴In all but the Very Easy puzzles, unless you have a genius-level memory with nothing more pressing to occupy it, you will need to make use of Candidate ("little") numbers to keep track of which numbers could potentially be the solution for a Cell. Then you will go through and erase these Candidates one by one (based on the solving techniques described in later tutorials) until left with only one Candidate, which will become a Big Number (i.e. the solution to the Cell.)

¹⁵To see this process in action it is recommended that you now generate an Easy puzzle and use the Guided Solve to watch the solution unfold step-by-step. Use the links to the Tutorials for techniques that you are unfamiliar with.

This ends the Sudoku Intro tutorial.