Hidden Quad
Four values only fit in the same four cells of a row or column — strip those cells down to just those four.
The solver does not attempt this technique, so Smart Hint will never suggest it. It is documented because you may still want to spot it yourself.
How it works
- 1In this 6-cell row, candidates 1, 2, 3 and 4 occur only in the first four cells. The last two cells can take only 5 or 6.
- 2Four values with only four homes form a Hidden Quad: those first four cells must be occupied by 1, 2, 3 and 4 in some order.
- 3Remove the extra 5s and 6s from the quad. Unlike a Naked Quad, this pattern is found by tracking the values' homes rather than the cells' combined candidates.
- 4The leftovers, {5,6} and {5,6}, are again a Naked Pair striking the same four candidates, and again the ladder gets there first. A hidden quad among b blanks is a naked set on the other b − 4, so even a seven-blank row leaves only a Naked Triple behind — there is no board this game deals where the cheaper name does not exist.
- Candidates this technique rules out
- Cells read together — The connecting line shows which cells combine to make the deduction.
- Conclusion — The coloured candidate, or the final arrow when it lands outside the pattern, shows the result.