Hidden Unique Rectangles
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.
How it works
- 1B1, E1, B2 and E2 form a rectangle across two rows, two columns and exactly two boxes — the only shape a uniqueness argument can sit on — and all four carry {4, 6}.
- 2Only B1 is a bare pair; the other three hold extras, so none of the plain Unique Rectangle types can see the pattern at all.
- 3Digit 6 is strongly linked along E2's row (E2 ↔ B2) and down its column (E2 ↔ E1): in each of those units, 6 has only those two homes left.
- 4Suppose E2 were 4. Then it isn't 6, so both strong links fire and force 6 into B2 and E1. B1 sees both, so B1 can't be 6 — it must be 4, and the four corners come down to a {4, 6} rectangle that could swap. Two solutions; so E2 isn't 4.
- First colour in the chain
- Second colour in the chain
- Cells that establish the pattern
- Where the conclusion lands
- Candidate ruled out