Clue cell
The dark cell in a kakuro grid carrying the target sums for the runs extending from it — usually one or two numbers separated by a slash.
A clue cell is the dark cell in a kakuro grid that carries the target sums for the white-cell runs extending from it. Visually, clue cells look like the black squares in a crossword, but they hold information: a number above the diagonal for the column run extending downward, a number below the diagonal for the row run extending to the right, or both.
Reading a clue cell
The standard notation places two numbers split by a slash. The number in the upper-right (or before the slash) is the down clue — the target sum for the column run that descends from the clue cell. The number in the lower-left (or after the slash) is the across clue — the target sum for the row run extending to the right. A clue cell with only an across clue has no column run extending down (the cell below is also dark); a clue cell with only a down clue has no row run.
Some kakuro grids use slightly different notations — small numerals stacked top and bottom, colour-coded numbers, or symbol prefixes — but the underlying meaning is always the same: a target sum for the run starting in the indicated direction.
How clue cells anchor the puzzle
Every white entry cell is constrained by exactly one clue's column-run target (the clue cell directly above the entry cell's column run) and one clue's row-run target (the clue cell directly to the left of the entry cell's row run). Those two clue cells are the anchors of the deduction for that entry cell — every digit it can hold must satisfy both clues' targets in combination with the run's other entry cells.
Clue cells themselves are never filled — they're the structural skeleton of the puzzle, not part of the answer. Solving a kakuro is the act of filling every entry cell with a digit that satisfies the constraints of the two clue cells it answers to, plus the no-repeats-in-run rule.
Visual variations across publishers
Some kakuro grids use a single clue cell to start a run that bends — a clue cell at the top of a column might mark the start of a "compound run" that turns at a corner. These compound or "L-shaped" runs are unusual in standard kakuro and not used in Sudoku Mountain's puzzles. The standard shape is what readers will encounter elsewhere on the site: each clue cell anchors at most one row run and one column run, and runs go in straight lines.
See also
- Kakuro— A Japanese number-placement puzzle. Cross-sums act like a crossword grid; players fill white cells with digits 1–9 so each run sums to its target without repeating a digit.
- Run (kakuro)— A horizontal or vertical sum-segment in a kakuro grid. The white cells from one clue cell to the next, which must sum to the clue's target without repeating a digit.
- Entry cell— A white cell in a kakuro grid that the player fills with a digit. Each entry cell belongs to exactly two runs — one horizontal, one vertical — and must satisfy both.
Read more
- Meet Kakuro
An introduction to Kakuro — what it is, how it differs from Sudoku, and why people who like number-logic puzzles often end up preferring it.