Hidden Unique Rectangles
Extreme
Used by Smart Hint
A Unique Rectangle deadly pattern hidden behind extra candidates, uncovered via strong links on one of the pattern's two digits instead of bare bivalue corners.
- First colour in the chain
- Second colour in the chain
- Cells that establish the pattern
- Where the conclusion lands
- Candidate ruled out
How it works
- B1, E1, B4, and E4 all carry {4, 6}, but only B1 is a bare pair — the others hold extra candidates, so a plain Unique Rectangle can't see the pattern.
- Digit 6 is strongly linked along E4's row (E4 ↔ B4) and along its column (E4 ↔ E1): in each of those units, 6 has only those two homes left.
- Suppose E4 were 4. Then it isn't 6, so both strong links fire and force 6 into B4 and E1. B1 sees both, so B1 can't be 6 — it must be 4. That leaves all four corners holding only 4s and 6s in a pattern that could swap, giving the puzzle two solutions. So E4 can't be 4.