Sudoku glossary

The terms Legen uses in puzzles and explanations.

These definitions keep coordinates, candidate reasoning, proof steps, and difficulty facts consistent across the English, Chinese, and Japanese pages.

Cell

One square in the 9×9 grid. Legen names it by row and column, such as r3c7.

Row

One horizontal set of nine cells, numbered 1 through 9 from top to bottom.

Column

One vertical set of nine cells, numbered 1 through 9 from left to right.

Box

One 3×3 region. The nine boxes are read left to right, top to bottom.

Unit

Any row, column, or box that must contain the digits 1–9 exactly once.

Given

A digit fixed by the published puzzle. A player cannot edit a given.

Candidate

A digit that can still legally occupy an empty cell under the current verified state.

Placement

A verified proof step that writes one digit into one cell.

Candidate elimination

A verified proof step that removes one or more candidates without filling a cell.

Proof

Immutable structured data describing why a placement or elimination is valid for one exact board revision.

Logic coverage

“Complete” means the fixed engine reached a solved board using only supported verified steps.

LDI

The Legen Difficulty Index: a versioned 0–100 engine-relative score, not a human ability score.

Puzzle ID

A stable content-derived identifier shared by every language and asset for the same givens.