Kakuro (クロスサム, "cross sum") is a Japanese logic puzzle that blends crossword structure with arithmetic. Every puzzle has exactly one solution, reachable by pure logic — no guessing needed.
Rules
1
Read the clues
Black cells contain clue numbers. The number in the upper-right triangle is for the column run going down; the number in the lower-left triangle is for the row run going right.
2
Fill white cells with 1–9
Tap a white cell to select it, then tap a number on the pad (or type on your keyboard). Each digit must be 1 through 9 — zeros aren't allowed.
3
Make every run sum correctly
Every consecutive sequence of white cells (horizontally or vertically) must add up to its clue value. A 3-cell run with clue "6" could be filled with 1, 2, 3.
4
No repeating digits per run
Within any single run, each digit can appear only once. You can't use "3+3" for a 2-cell run summing to 6 — you must use "1+5", "2+4", etc.
Strategy Tips
💡 Start with forced cells
Some (length, sum) combinations only have one valid set of digits. A 2-cell run summing to 3 must always be {1, 2}. Look for these first.
💡 Use intersections
Horizontal and vertical runs share cells. If a cell's row-run can only contain {1, 2, 4} and its column-run can only contain {2, 5, 8}, the only option is 2.
💡 Pencil marks are your friend
Use pencil mode (✏️) to note all possible values in a cell. As you fill in other cells, eliminate impossible candidates.
💡 Check the sum as you go
If a run is almost complete and the partial sum is approaching the target, you can often deduce the last cell's value directly.
Forced Combinations Reference
Some (length, sum) pairs have only one valid digit set — these are the best starting points.