What are the rules of Kakuro?

Enter one digit from 1 through 9 in each white cell. An across run begins to the right of its arrow clue, and a down run begins below its downward arrow clue. Every uninterrupted run must add to its clue with no repeated digit. A two-cell sum of 3 uses 1 and 2 in some order; the crossing clues determine that order. Zero means an empty cell and is not an answer digit.

How are these puzzles generated?

The original generator creates connected diagonal grids with two- and three-cell white runs, fills them with distinct digits and derives their crossing sum clues. A bounded exact solution counter must prove exactly one solution before the puzzle is offered. It stops counting at a second solution and does not label an exhausted search unique. Generation tries at most 128 candidates and 500000 proof nodes, with an eight-second worker limit. Failure or cancellation keeps the prior puzzle. These grids are not assigned difficulty ratings.

How do pencil notes and undo work?

Select a white cell and turn on Pencil notes to toggle candidate digits separately from the actual grid. Notes do not contribute to sums and never count as digit submissions. A changed nonzero actual digit adds one submission, including a mistake. Clearing and unchanged digits add none. Undo removes the last digit or note change and removes its digit submission when applicable; redo restores it. Notes can be entered only in blank cells.

How is the challenge scored?

The fixed challenge is a seeded original 7 × 7 grid, including its clue border. Score is max(0, 1000 minus final retained digit submissions), within 0–1000; higher is better. Hints, answer reveal, answer-key printing before completion, restored progress and previously opened equivalent puzzles stay practice. Scores are self-reported. Checking the current rules does not reveal an answer, and reviewing an earned completion preserves its score.

What happens when someone opens a challenge link?

The landing screen shows the shared score and fixed rules, then offers Start same challenge. It does not automatically start a puzzle. After a fresh unassisted completion, it displays both scores, a signed difference and whether the new score is better, tied or lower. Copy, native share and a result-card PNG become available, with a new link carrying the recipient's score for the same seed. Links contain no digits, notes or play history.

Can I print a blank grid or resume locally?

Print puzzle includes only the original sum clues and blank white cells. Print puzzle and answer key adds a separate page and makes unfinished play assisted practice. Local saves exclude the solution. Resume regenerates and validates the exact original grid and clues, then replays the digit and pencil-note history as practice. Up to 10000 retained changes and 1024 local exposure fingerprints are supported; rotated or reflected equivalents share an exposure identity. Storage failure leaves the current puzzle in memory.

Can I use the keyboard on a small screen?

Yes. Select a white cell or use the coordinate selector, then press 1–9 to enter a digit and Backspace or Delete to clear. Arrow keys move between playable cells. The digit keypad and every white cell have 44-pixel targets, and the board scrolls inside its panel. A full text list gives every across and down clue with its current sum, blank count and rule status.

Kakuro Puzzles

Fill an original cross-sum grid with digits 1–9. Every uninterrupted across or down run must add to its clue, and a run cannot repeat a digit. Generate a 3 × 3 through 9 × 9 board, including its clue border, use separate pencil notes and check both crossing sums. Print the original clues or request a separate answer key. A fresh 7 × 7 completion can share its self-reported submission score for the same puzzle.

Original cross-sum puzzles. Each white cell belongs to an across run and a down run. Both sums must match their clues without any repeated digit in a run.

Puzzle controls3 × 3 through 9 × 9, including clue border

Grid sizeOriginal seed

Crossing sums and no repeatsWaiting for a puzzle

Each run is distinct
A two-cell clue of 3 uses 1 and 2, in either order. It cannot use 1 twice. The crossing run decides the order.

Both directions count
Every white cell belongs to two uninterrupted runs, one across and one down. The digit must satisfy both clues.

One verified solution
Original connected grids use two- and three-cell runs. Generation tries up to 128 candidates and 500000 proof nodes, with an eight-second worker limit. A failed or ambiguous candidate is never offered as unique.

Choose a size and seed, then generate an original cross-sum puzzle.

Clue 3, two cellsThe digits are 1 and 2; the crossing clues determine their order.
Pencil notesKeep possible digits separately from the actual grid. Notes do not affect sums or score.
Print and resumePrint the original clues with a separate answer page only when requested. Resume regenerates and validates locally saved progress as practice.

Accuracy. Every uninterrupted run matches its clue and contains no repeated digit. Generate original uniquely solvable puzzles with a bounded solution counter; timeouts are explicit.

Common questions

What are the rules of Kakuro?: Enter one digit from 1 through 9 in each white cell. An across run begins to the right of its arrow clue, and a down run begins below its downward arrow clue. Every uninterrupted run must add to its clue with no repeated digit. A two-cell sum of 3 uses 1 and 2 in some order; the crossing clues determine that order. Zero means an empty cell and is not an answer digit.
How are these puzzles generated?: The original generator creates connected diagonal grids with two- and three-cell white runs, fills them with distinct digits and derives their crossing sum clues. A bounded exact solution counter must prove exactly one solution before the puzzle is offered. It stops counting at a second solution and does not label an exhausted search unique. Generation tries at most 128 candidates and 500000 proof nodes, with an eight-second worker limit. Failure or cancellation keeps the prior puzzle. These grids are not assigned difficulty ratings.
How do pencil notes and undo work?: Select a white cell and turn on Pencil notes to toggle candidate digits separately from the actual grid. Notes do not contribute to sums and never count as digit submissions. A changed nonzero actual digit adds one submission, including a mistake. Clearing and unchanged digits add none. Undo removes the last digit or note change and removes its digit submission when applicable; redo restores it. Notes can be entered only in blank cells.
How is the challenge scored?: The fixed challenge is a seeded original 7 × 7 grid, including its clue border. Score is max(0, 1000 minus final retained digit submissions), within 0–1000; higher is better. Hints, answer reveal, answer-key printing before completion, restored progress and previously opened equivalent puzzles stay practice. Scores are self-reported. Checking the current rules does not reveal an answer, and reviewing an earned completion preserves its score.
What happens when someone opens a challenge link?: The landing screen shows the shared score and fixed rules, then offers Start same challenge. It does not automatically start a puzzle. After a fresh unassisted completion, it displays both scores, a signed difference and whether the new score is better, tied or lower. Copy, native share and a result-card PNG become available, with a new link carrying the recipient's score for the same seed. Links contain no digits, notes or play history.
Can I print a blank grid or resume locally?: Print puzzle includes only the original sum clues and blank white cells. Print puzzle and answer key adds a separate page and makes unfinished play assisted practice. Local saves exclude the solution. Resume regenerates and validates the exact original grid and clues, then replays the digit and pencil-note history as practice. Up to 10000 retained changes and 1024 local exposure fingerprints are supported; rotated or reflected equivalents share an exposure identity. Storage failure leaves the current puzzle in memory.
Can I use the keyboard on a small screen?: Yes. Select a white cell or use the coordinate selector, then press 1–9 to enter a digit and Backspace or Delete to clear. Arrow keys move between playable cells. The digit keypad and every white cell have 44-pixel targets, and the board scrolls inside its panel. A full text list gives every across and down clue with its current sum, blank count and rule status.

Every uninterrupted run matches its clue and contains no repeated digit. Generate original uniquely solvable puzzles with a bounded solution counter; timeouts are explicit.