When a Sudoku is actually hard

A hard Sudoku is not an empty-looking grid. Beginner boards can look sparse. Hard boards ask for longer chains: this digit lives here, so that one cannot, so the next cell is forced.

The bands run from Beginner through Extreme. They describe the kind of reasoning, not how many cells start empty. A crowded Medium can still be gentle. A Hard with more givens can still ask you to sit.

If you are scanning last empty cell and only-one-place and still stuck, you have left the easy work. Use Notes. Then look for a digit that lives in one row of a box. Then wait.

You can leave it and Continue. You can open a lower band. Hard is a kind of thinking, not a test, and time stays private. How to play Sudoku holds the first scans. Play Sudoku when you want the board.

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