Sudoku

Nine of everything, once each.

The classic number puzzle on a 9×9 grid split into nine 3×3 boxes, graded honestly from gentle to genuinely hard. It appears on every daily page.

How to play

Fill every blank so each row, column and 3×3 box holds 1 to 9 exactly once. Givens are in ink; your digits are in sage.
Not sure yet? Pencil marks keep your candidates small and quiet.
In Relaxed mode a wrong digit shows in clay. In Challenge mode nothing is marked. The puzzle finishes when every digit is right.

Tips and tricks

Find the last empty square. A row, column or box with eight digits already has only one answer for its ninth.
Scan one digit at a time. Pick a digit and look across each box. Where its row and column are already blocked, the digit may have only one place left.
Look for hidden singles. A digit that fits in just one square of a box, row or column belongs there, even if that square has other candidates.
Use pairs. If two squares in a row can only be the same two digits, those digits are taken. Remove them from every other square in that row.
Box and line. If a digit's candidates inside one box all sit in a single row, it cannot appear anywhere else in that row.
Pencil late, not never. Fill the easy digits first. Bring in pencil marks when the obvious moves run out.

Where to find it

It appears on every daily page, and the Library has Easy, Medium and Hard tracks of it. Stuck? A hint costs ink drops, and Inkbloom Plus makes hints unlimited.