Hidden Pair
Hard
Used by Smart Hint
Two digits appear as candidates in only the same two cells of a unit — strip those cells down to just those two digits.
- Cells that establish the pattern
- Candidate ruled out
How it works
- In this box, digits 1 and 5 only appear as candidates in G1 and H2 — no other cell in the box can hold either digit.
- That makes {1, 5} a Hidden Pair: strip every other candidate from those two cells, removing the 8 and 7 that were also sitting there.