Intermediate Sudoku is where simple scanning stops working reliably and you start solving via structure. The goal is to reduce candidates using relationships between cells—not just obvious missing digits.
If two cells in a unit (row/column/box) share the same two candidates, those candidates cannot appear elsewhere in that unit.
If two digits can only appear in two cells within a unit (even if those cells have other candidates), remove the extra candidates from those two cells.
If a digit in a 3×3 box can only go in one row (or column), eliminate that digit from the rest of that row (or column) outside the box.
Reverse of pointing: if a digit in a row can only appear within one box, remove that digit from the other cells of that box.
One elimination can create a pair, which creates another elimination, which reveals a single. Intermediate solving often requires following these cascades.
**Do I need X-Wing at intermediate?** Usually not.
**Should I guess?** No.
**Why do I stall?** You’re still in “placement mode.” Switch to elimination mode.
Intermediate Sudoku is the turning point where Sudoku becomes structural reasoning. Master pairs and box-line interactions and medium puzzles become manageable.