Kakuro

What is Kakuro?

Kakuro is a crossword written in digits. Instead of words, each run of white cells holds digits from 1 to 9, and instead of definitions, the dark cells give sums: the number at the start of a run is what its digits add up to. No run uses the same digit twice.

The game mixes a little arithmetic with a lot of logic. Every board has exactly one answer, reached by reasoning and never by guessing. There are three sizes, and every day brings a new board, the same for everyone.

How to play Kakuro

Tap a white cell to select it, then tap a digit on the pad; tap the same digit again to take it out.

• Runs. A run is an unbroken line of white cells, across or down. Its digits add up to its sum and never repeat.
• Sums. In a dark cell cut by a diagonal, the number under the diagonal belongs to the run going down from it, and the number over the diagonal to the run going right.
• Mistakes. A digit repeated in a run turns red, and so does a sum the digits already in its run can no longer reach. A run that adds up fades.
• Notes. Turn on Notes to write small digits in a cell; a digit you place disappears from the notes in both its runs. On a computer keyboard, digits, arrow keys and N for notes all work.
• Undo. Undo takes back your last change, a digit or a note, as often as you like and at no cost.
• Score. Your score is the time to solve the board, plus 30 seconds per hint. Each size has its own leaderboard.

Tips and strategy

1. Sums with one answer. In two cells, 3 is always 1 and 2, 4 is 1 and 3, 16 is 7 and 9, and 17 is 8 and 9. In three cells, 6 is 1, 2 and 3, 7 is 1, 2 and 4, 23 is 6, 8 and 9, and 24 is 7, 8 and 9. Start there.
2. Crossings. Every white cell sits in one run across and one run down, so it can only hold a digit both allow. Where a 4 in two cells (1 and 3) crosses a 7 in three cells (1, 2 and 4), the shared cell is 1.
3. Digits a sum needs. Some digits are in every way of making a sum: 10 in four cells is always 1, 2, 3 and 4. If only one cell of the run can take one of them, it goes there.
4. Small sums, small digits. In two cells adding up to 5, neither cell can hold 5 or more; in two cells adding up to 15, neither can hold less than 6.
5. Note the options. On the bigger boards, write each cell's possible digits as notes and strike them out as the crossings settle.

Frequently asked questions

Is Kakuro free?

Yes. Like every game on Play, it runs free in your browser, with no download and no account.

Where does the name come from?

Kakuro is a Japanese contraction of "kasan kurosu", addition cross. In English the same puzzle is also known as Cross Sums.

What does a hint do?

It first fixes a wrong digit if there is one, otherwise it fills in the cell reasoning reaches next. Each hint adds 30 seconds to your time.

What do the levels mean?

Easy is a 6 by 6 board with short runs and many sums that have a single answer. Medium is 8 by 8. Hard is 10 by 10, with runs of up to six cells, fewer easy ways in, and steps such as finding the one cell left for a digit a sum needs.

What is today's board?

Every day everyone gets the same medium board, so times compare directly on the leaderboard.