Medium Sudoku

A medium Sudoku has fewer starting numbers than easy, so plain scanning runs out sooner and you begin using pencil marks and simple patterns — but it never demands the advanced techniques of a hard board. There is still a single logical solution and no guessing required.

New to candidates and patterns? The tips & strategy guide walks through naked and hidden singles, pairs and pointing pairs in the order you will use them.

Every medium board has a moment where the easy moves run out — solvers call it hitting the wall, and how you respond to it is the whole skill of this level. The wrong response is to stare harder at the same cells. The right one is to switch questions. Scanning asks "where does this digit go?"; when it stalls, start asking the reverse for the emptiest cells: "what can this cell still be?" A cell that answers with a single candidate is a naked single, and it is invisible to digit-by-digit scanning — which is exactly why the wall feels like a dead end when it is not.

If neither question produces a move, add pencil marks — but only to the two or three most constrained units, not the whole board. A fully annotated medium board drowns you in notes it never needed; a selectively annotated one shows you the hidden single or naked pair immediately. Medium boards are tuned so this second gear is always enough.

Medium boards are cleared by three patterns, in roughly this order of frequency: the hidden single — a digit with only one possible home in a row, column or box, even though that cell has other candidates; the naked pair — two cells in one unit sharing the same two candidates, which lets you erase those digits everywhere else in the unit; and the pointing pair — a digit confined to one row inside a box, which removes it from the rest of that row outside the box.

Notice what is not on the list: X-Wings, swordfish, colouring. Medium never requires them, so if you find yourself reaching for heavy machinery, the simpler pattern you missed is still sitting on the board. That discipline — trusting the level to be honest about its ceiling — is what makes medium such good training for hard.

Medium is where Sudoku feels just right for most people — enough challenge to be absorbing, not so much that you get stuck. It is the natural step up once easy boards feel automatic, and a satisfying few-minute solve for a break.