Are jigsaw puzzles harder than classic?

Often slightly, because the irregular regions break the visual habits you build on 3×3 boxes — but the logic is identical.

How many cells per region?

Exactly nine, the same as a classic box; only the shape differs.

What is the law of leftovers?

A jigsaw-specific shortcut: when a region and a set of complete rows or columns cover almost the same cells, the small set of cells that differ must hold identical digits. It often forces a placement directly, without any candidate scanning.

Jigsaw Sudoku Rules

Sudoku where the nine regions are irregular jigsaw shapes instead of 3×3 boxes.

Jigsaw Sudoku (also called Squiggly or Geometric Sudoku) replaces the nine 3×3 boxes with nine irregular, interlocking regions. Every other rule stays the same: each of those regions, like each row and column, must contain 1–9 once.

The irregular regions change the geometry of the deductions, so familiar box-scanning patterns look different.

The rules

Fill every cell with a digit from 1 to 9.
Each row contains all nine digits once.
Each column contains all nine digits once.
Each irregular jigsaw region contains all nine digits once.

Irregular regions

Each region still holds nine cells and still needs the digits 1–9, but its shape winds across the grid. Because regions are not aligned to neat thirds, locked-candidate and pointing patterns become especially powerful.

A 9×9 jigsaw sudoku grid with three irregular nine-cell regions tinted and outlined instead of square boxes. — Jigsaw regions: nine cells each, any connected shape — and each still takes 1–9 exactly once.

Solving strategy

Jigsaw rewards the "law of leftovers": where a region and a band of rows or columns nearly coincide, the few cells of difference must contain the same digits. Comparing a region against the rows it mostly fills often pins a digit with no scanning at all. Beyond that, every classic technique applies — but think in terms of the squiggly region wherever you would normally use a box.

Pointing and box/line reduction are unusually strong here because a region can share many cells with a single row or column, so a digit confined to a region frequently collapses onto one line.

Use the law of leftovers between a region and a row/column band.
Substitute "region" for "box" in every box-based technique.
Watch for regions that hug a single line — strong pointing eliminations.

Frequently asked questions

Are jigsaw puzzles harder than classic?: Often slightly, because the irregular regions break the visual habits you build on 3×3 boxes — but the logic is identical.
How many cells per region?: Exactly nine, the same as a classic box; only the shape differs.
What is the law of leftovers?: A jigsaw-specific shortcut: when a region and a set of complete rows or columns cover almost the same cells, the small set of cells that differ must hold identical digits. It often forces a placement directly, without any candidate scanning.

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