Nine
Naked triple
A technique Nine explains
Like a naked pair, but with three cells sharing exactly three digits between them. A cell does not need all three; together they must be exactly three.
Example
6498527318754931267984514398595757169798245341927894
These three cells in row 8 share exactly 3, 5 and 6 between them. Those three digits are theirs, so they are out in the rest of row 8. That leaves one cell with only one digit left: 2.
In the app
Nine is the sudoku that writes this reasoning itself, on every puzzle, in the app. The explanation fills in nothing: it names the technique, colours the proof and says why. Free for seven days, then a one-time unlock. No ads, no account, no internet needed.
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