Chaos Construction
You must determine the region boundaries as part of solving
Chaos Construction is fully playable. Choose a difficulty and start solving.
Chaos Construction Sudoku gives you no pre-defined regions at all. Instead, you must deduce both the digit placements AND where the nine 9-cell regions are located, while satisfying all standard Sudoku row/column rules. This is the most open-ended Sudoku variant — the puzzle defines enough constraints (often through lines or other rules) to uniquely determine both the grid and the region structure.
Like all Sudoku variants, Chaos Construction builds on the classic 9×9 foundation. Every row, column, and 3×3 box must contain each digit from 1 to 9 exactly once. The variant constraint is added on top of these standard rules, never replacing them.
If you're new to Sudoku, start by learning the basic rules and techniques before attempting variants.
Techniques Useful for This Variant
| Technique | How it applies |
|---|---|
| Pencil Marks / Notes | Essential for tracking candidates alongside the variant constraint |
| Obvious Singles | Cells narrowed to one candidate by the combined constraints |
| Hidden Singles | Digits with only one valid cell in a unit after variant elimination |
| Pairs and Triples | Locked candidates exposed by the additional constraint |