Meet Kakuro

Kakuro is the other big number-logic puzzle. Like Sudoku, it uses digits 1 through 9 and a fill-in-the-grid format. Unlike Sudoku, the grid is shaped more like a crossword than a square block, and the rules are about sums rather than rows-columns-and-boxes.

If classic Sudoku is the world's most famous logic puzzle, Kakuro is the one its enthusiasts often graduate to. Some people who never click with Sudoku take to Kakuro on their first puzzle. Others bounce off Kakuro and stay on Sudoku forever. The difference is mostly in the kind of constraint your brain finds satisfying.

How Kakuro differs from Sudoku

The grid is laid out like a crossword. Black squares divide the grid into runs of white squares, and each run has a target sum displayed at its start in a triangular split-box, like a crossword clue. The rules:

1. Fill every white square with a digit from 1 to 9.
2. Each horizontal run must add up to the sum displayed at its left end, with no repeated digits inside the run.
3. Each vertical run must add up to the sum displayed at its top, with no repeated digits inside the run.

That's it. There's no 3×3 box rule, no row-of-nine constraint, no fixed grid size. Kakuro grids range from small 5×5 starters to 15×15 monsters. The arithmetic is the puzzle.

How the experience differs

Sudoku is mostly visual. You scan rows and columns and boxes, your eye finds patterns, and the placement happens once the constraints have lined up. Pencil marks track candidates, but most easy and medium moves are visible without writing anything down.

Kakuro is mostly arithmetic. Each run has a small library of valid digit combinations — a three-cell run summing to 6 must be 1+2+3 (only combination); a two-cell run summing to 17 must be 8+9 (only pair). Solving Kakuro is largely about identifying these constrained runs, intersecting their possible digits with the constraints from crossing runs, and narrowing each cell's options that way.

The arithmetic isn't hard — every Kakuro can be solved with single-digit addition — but the satisfaction is different from Sudoku's. Where Sudoku says "this cell can only hold this digit because the digit is needed elsewhere," Kakuro says "this cell can only hold this digit because nothing else makes the sum work."

The other shift is grid size. Sudoku is fixed at 9×9, while Kakuro grids vary considerably — from 5×5 starters that finish in five minutes to 15×15 expert puzzles that can take an hour or more. The longer puzzles are a different cognitive shape from any Sudoku, requiring you to hold a larger problem space in your head while working a single run.

Where to start

Kakuro's beginner cliff is steeper than Sudoku's. The combinatorics aren't intuitive at first — you have to learn that two-cell runs summing to 17 are uniquely 8+9, that three-cell runs summing to 7 are uniquely 1+2+4, and so on. There's a small cheat-sheet of "essential combinations" that most beginners refer to for their first ten or so puzzles before the patterns become habit.

If you're starting from zero, our Kakuro easy puzzles at 5×5 are the right starting point — small enough to finish in five or ten minutes, long enough to surface the recurring combinations you'll need to recognise. Don't expect speed on the first one; expect the same gradual pattern recognition any puzzle requires.

The honest summary: Kakuro and Sudoku are cousins, not the same puzzle. Some solvers find Sudoku's elegance more pleasant than Kakuro's arithmetic; others find Kakuro's combinations more satisfying than Sudoku's pattern recognition. Trying one Kakuro puzzle costs nothing, and the verdict comes quickly. If it clicks, you've found a new puzzle to fold into your day.