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The rules:
- Every row holds the numbers 1 to 9 once.
- Every column holds the numbers 1 to 9 once.
- Every region, the shapes inside the thick borders, holds the numbers 1 to 9 once.
You may know it as Irregular Sudoku, Squiggly Sudoku or Geometry Sudoku. It is the same puzzle under different names. Here, every game draws a fresh set of regions, so no two games look alike.
How to play
Play it like classic Sudoku, with one change of habit. In normal Sudoku your eyes learn where the boxes are and stop thinking about it. In Jigsaw you have to follow the borders. Selecting a square shades its whole region, which makes this much easier.
Start with the odd shapes
Long thin regions are your friends. A region that runs along most of a row shares many squares with that row, so whatever is missing from the rest of the row is pinned down quickly. Regions that wrap around a corner work the same way with a column.
Scan by number
Pick a number, say 4, and go region by region. For each region that has no 4 yet, cross off the squares that already see a 4 in their row or column. When only one square is left, that is your 4.
The trick only Jigsaw has: leftover squares
Take the top three rows. Together they hold each number exactly three times. Now look at the regions that sit completely inside those three rows: they also hold each number once each. Take them away, and what remains on both sides must match.
In practice that means: the squares of those rows that belong to other regions, and the squares of those regions that poke out below the rows, contain the same set of numbers. If one side is already known, so is the other. Puzzle fans call this the law of leftovers. It is the main reason a Jigsaw puzzle can have fewer starting numbers than a classic one.
The four levels
| Easy | About 38 starting numbers. Scanning gets you to the end. |
|---|---|
| Medium | About 32. Notes help in the trickier regions. |
| Hard | About 28. Expect to use pairs and the leftover trick. |
| Expert | About 25. Few easy starts, notes needed across the board. |
Questions people ask
What is Jigsaw Sudoku?
Jigsaw Sudoku is Sudoku where the nine 3 by 3 boxes are replaced by nine odd shaped regions of nine squares each. Every row, column and region must still hold the numbers 1 to 9 once.
Is Jigsaw Sudoku the same as Irregular Sudoku?
Yes. The same puzzle is also sold as Squiggly Sudoku, Geometry Sudoku and Nonomino. The names differ by publisher, the rules are the same.
Is Jigsaw Sudoku harder than normal Sudoku?
It feels harder at first, because the region shapes make scanning less automatic. The logic is the same, and once you get used to following the thick borders, a Jigsaw puzzle at a given level plays about as hard as a classic one.
Is the layout the same every time?
No. Every game builds a new set of regions, so you never play the same shapes twice. Each layout is checked to make sure the puzzle has one answer.
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