Medium sudoku

Singles alone won't always get you to the end here. Medium puzzles bring in locked candidates — specifically the "pointing" pattern, where a digit's remaining spots inside one box are all stuck in a single row or column, which lets you clear that digit from the rest of that row or column outside the box. It's the first technique that asks you to look at a box and a line together, instead of one unit at a time.

That's also the entire jump from easy: once you've found the pointing pattern (or it turns out you don't need it on a given puzzle), the rest usually falls back to the same naked and hidden singles from the easy level. Medium is where most people land once the training wheels come off.

A quick way to spot it

Scan a box and ask: for some digit that's missing, do all of its possible homes sit in the same row? If three cells in a box could each hold a 6, and all three happen to be in row 4, then no other cell in row 4 — outside that box — can be a 6 either. That's the whole trick.

If you're stuck

Turn on notes (press N or tap the pencil icon) and mark every candidate in a crowded box. The pointing pattern is much easier to see written down than held in your head. If it's still not clicking, the hint button will show you exactly where one is and explain why, cell by cell.

Comfortable here? Hard adds pairs — two cells, two digits, one elimination — to the toolkit.