Kakuro is a cross-sums puzzle. The grid is a mix of black clue cells and white entry cells. Each run of white cells — horizontal or vertical — must sum to the number in the black cell at its head, and no digit can repeat within a single run.

The small number in a clue cell's top-right corner is the target for the run going right; the number in the bottom-left corner is the target for the run going down. Digits are always 1 through 9.

Start with the most constrained runs: two cells summing to 3 must be 1+2; three cells summing to 6 must be 1+2+3; two cells summing to 17 must be 8+9. Intersect these forced digit sets against the runs they cross to lock in individual cells.

Easy puzzles are the best place to start — cells contain more starting digits than medium or hard, so a beginner can see a path forward without techniques beyond basic scanning.

Playing Sudoku regularly helps train concentration and working memory. A few easy puzzles a day is enough to notice your scanning speed improve over a couple of weeks.