Between Lines Sudoku
Digits on a line must fall strictly between the two endpoint values
Between Lines Sudoku is fully playable. Choose a difficulty and start solving.
Lines run between two circled cells, and every digit on the line must fall strictly inside the two endpoint values. Wide-apart endpoints barely constrain; close endpoints choke the line — deducing which is which is the puzzle. Range logic, no sums, mid-tier difficulty.
For the complete rules, worked examples and solving techniques, read the full How to Play Between Lines Sudoku guide.
Like all Sudoku variants, Between Lines Sudoku 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 |