Sudoku Rules
Sudoku is a Japanese puzzle where you need to write numbers according to specific algorithms (so they don't repeat vertically, horizontally, or diagonally). In simple Sudoku, you need to fill in the missing numbers in 3x3 cells. Complex Sudoku can have more than three rows and three columns, up to 6x6, 9x9, or more cells.
In the classic Sudoku version, you have nine three-by-three blocks where you need to enter numbers from one to nine. The basic rules are as follows:
- · Vertical numbers cannot be repeated.
- · Horizontal numbers cannot be repeated.
- · Numbers can only appear once in 3x3 squares.
The rules of classic Sudoku mean that some numbers are already fixed at the beginning. This makes it easier to analyze the grid and find the missing values. The number of empty cells and numbers depends on how challenging you want the puzzle to be. The higher the challenge level, the fewer cells are filled in (so you need to use specific techniques to quickly and accurately fill the entire grid).
Once you enter all the numbers into the fields, you're done. You can continue to the next one.
Sudoku Techniques
Last Free Cell
Master the "Last Free Cell" technique, the most basic and essential Sudoku strategy. This guide shows you how to instantly solve a cell by finding the one missing number (1-9) in any 3x3 block, row, or column that has only one empty space left.
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Last Remaining Cell
Master the "Last Remaining Cell" technique, a key Sudoku strategy. This guide teaches you how to hunt for a specific number (e.g., '8') within a block by using intersecting rows and columns to eliminate all other possible cells for it.
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Last Possible Number
Master the "Last Possible Number" technique, a simple Sudoku strategy for beginners. This guide teaches you to find the value of a single empty cell by checking its row, column, and block to eliminate all "seen" numbers (1-9), leaving only the one possible answer.
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Sudoku Notes
Learn how to use Sudoku notes (candidates), the key to solving harder puzzles. This guide shows you how to mark notes correctly, using them as the foundation for advanced Sudoku techniques like X-Wings.
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Obvious Singles
Master the "Obvious Singles" technique (also "Naked Singles"). This guide shows the payoff of using Sudoku notes: when a cell has only one single candidate (note) remaining after eliminations, that note is the solution for that cell.
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Obvious Pairs
Master the "Obvious Pairs" technique (also "Naked Pairs"), a key advanced Sudoku strategy. This guide teaches you how to find two cells in the same house that only contain the exact same two candidates (e.g., {7, 9}), and then eliminate those candidates from all other cells in that house to crack the puzzle.
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Obvious Triples
Master the "Obvious Triples" technique (also "Naked Triples"), a powerful advanced Sudoku strategy. This guide teaches you to identify when three cells in a house lock in a set of three numbers (e.g., {1, 5}, {1, 8}, {5, 8}), allowing you to eliminate those three candidates from all other cells in that house.
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Hidden Singles
Master the "Hidden Singles" technique, a key Sudoku strategy. This guide teaches you how to scan an entire house (block, row, or column) to find a candidate (e.g., '1') that appears in only one cell, making it the hidden solution, even if other notes are present.
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Hidden Pairs
Master the "Hidden Pairs" technique, a powerful advanced Sudoku strategy. This guide teaches you how to scan an entire house to find two candidates (e.g., '2' & '6') that appear only in two cells, allowing you to eliminate all other "junk" notes from just those two cells.
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Hidden Triples
Master the "Hidden Triples" technique, a powerful advanced Sudoku strategy. This guide teaches you how to scan an entire house to find a set of three candidates (e.g., {5, 6, 7}) that appear only in three specific cells, allowing you to eliminate all other "junk" notes from just those three cells.
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