Box-Line Reduction
Medium
Used by Smart Hint
All of a digit's candidates in a row or column fall inside one box, so it can be eliminated from the rest of that box.
- Cells that establish the pattern
- Where the conclusion lands
- Candidate ruled out
How it works
- In row 1, every remaining candidate for digit 6 falls inside this box (A1 and C1) — nowhere else in the row allows it.
- That means 6 must land somewhere in row 1 of this box, so it can be crossed off the box's other rows — A2 and B3.