Medium Sudoku

The sweet spot: fewer clues than easy, but still fair. Medium Sudoku is where pencil notes and a little patience start to pay off.

The idea of a medium puzzle

Medium Sudoku is the natural home for most solvers. It gives you fewer starting numbers than an easy board, so you cannot simply scan your way to the finish, but it stops well short of the sparse, demanding grids of expert play. The result is a puzzle that asks you to think without ever feeling unfair. It is the level where Sudoku stops being a warm-up and becomes a genuine, satisfying challenge that still fits comfortably into a short break.

The rules

The rules never change. Fill the grid so that each row, each column and each 3×3 box holds the numbers 1 to 9 exactly once. Every board has a single solution and can be solved by logic alone.

How medium differs from easy

With fewer given numbers, the easy techniques run out sooner and you have to work harder for each placement. Two skills come to the front. The first is disciplined pencil-noting: marking the candidates for each empty cell so the board becomes a map rather than a guessing game. The second is the hidden single, a number that can legally go in only one cell of a row, column or box even though that cell still shows several candidates. Easy puzzles rarely need hidden singles; medium puzzles are built around them.

A steady method

• Fill in the obvious cells first to shrink the puzzle.
• Pencil in candidates for the rest, one unit at a time, so your notes stay accurate.
• Scan each row, column and box for a number with only one possible home.
• After every placement, clear that number from the notes of the cells it affects; the game does this for you automatically.

Work patiently and the board unravels itself. When two cells in a unit share the same two candidates and nothing else, you have found a naked pair, and those two numbers can be removed from every other cell in that unit. That single idea often breaks a medium puzzle wide open. If none of these moves appears at first, look again at your pencil notes rather than reaching for a guess. On a fair board there is always a legal deduction waiting, and medium puzzles are built so that a patient player can find the next one without any luck at all.

Common mistakes to avoid

Two habits trip up most solvers at the medium level. The first is guessing. If you ever find yourself placing a number you are not sure of, stop; a medium board never requires it, and one wrong guess can quietly poison the whole grid. The second is lazy notes. Half-finished pencil marks are worse than none, because they tempt you into false conclusions. Keep your candidates complete and up to date, erase them as placements rule them out, and let the game clear the obvious ones for you. Accurate notes turn a stubborn puzzle into a straightforward one.

Tools that help

Pencil notes, a hint button, undo and redo, a pause control and a solve timer are all built in, along with a Training mode that names and explains the next logical step. Your game saves automatically, and every board is generated fresh at the medium level.

Change of pace

Warm up on Easy Sudoku or push into Expert Sudoku when medium starts to feel routine. For a different challenge entirely, Killer Sudoku adds arithmetic cages, while Chain Sudoku offers a lighter, quicker puzzle. The classic board is always at Sudoku AZ.