Kakuro
Kakuro: cross sums to fill on a 7x7 grid. Any filling that satisfies every clue counts. Free, no install, works offline.
In Kakuro, each clue tells you the total of a run of squares beside or below it. Fill them with 1 to 9 so the run adds up, without repeating a digit inside it.
about 62.5 KB
Works offline after the first visit. No install, no sign-up.
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How to play Kakuro
Three kinds of square
Dark squares are not used at all. Some dark squares carry two small numbers split by a diagonal line: the one in the upper right is the total for the run to its right, and the one in the lower left is the total for the run beneath it. White squares are the ones you fill in.
Two rules for every run
A run is a line of white squares, going across or down. Its digits must add up to the clue, and no digit may appear twice inside the same run. The second rule is what separates this from a plain adding-up exercise — a run of three adding to six is 1-2-3, not 2-2-2, even though both add up.
You are checked against the clues, not against a stored answer
When you finish, the game goes through every run and checks two things: that its digits add up to the clue, and that none of them repeat. If both hold everywhere, you have solved it. That sounds like the obvious way to do it, but it is not the usual one — and it is the reason you can never be told you are wrong when you are not. Any filling that satisfies every clue counts, whether or not it is the particular one the puzzle was built from.
A run is never a single square
There are no one-square runs. A single square with a clue would amount to the answer written on the board, so the puzzle never contains one.
A run that adds up to too much turns red
If the digits you have put in a run already total more than its clue, that run is outlined in red. This follows from the rules alone, so it gives nothing away — it is the arithmetic you would do in your head anyway. A run that is wrong but not yet over its total is not flagged, because flagging that would mean checking against the answer.
Tap a square, then tap a number
Tap any white square to select it, which also shades the whole run it belongs to so you can see what you are working on. Then tap a number from 1 to 9 along the bottom, or the cross to clear the square. Arrow keys move the selection and the number keys work on a keyboard.
Kakuro Tips and Strategy
Solve the runs of two first
A run of two squares has only one possible pair for its total, so those runs settle instantly. Every square belongs to a run across and a run down, so a digit fixed in a short run narrows both of its other runs. Start there, and the harder runs tend to fall into place by elimination.
Use the red outline backwards
A run outlined in red has already gone over its clue, so the digit that pushed it past is wrong. Remove it and look at what is left: often exactly one digit fits the remaining total, and that digit is forced. The outline is pure arithmetic, so it never tells you more than you could work out yourself.
Cross-reference instead of guessing
A digit has to satisfy every run it sits in, so treat each square as the meeting point of two clues rather than solving runs one at a time. When a run's remaining total is small, list the combinations possible and see which fit the cross run too. A digit that works for only one of them is safe.
Kakuro — Frequently Asked Questions
Can a digit appear twice in the same run?
No. Every run uses each digit at most once, which is why a run of two squares can never hold two equal numbers.
I have filled a run so it adds up, but nothing is flagged. Is that right?
Yes. A run is only marked red when it has gone over its total, which is arithmetic you can check yourself. A run that adds up but conflicts with the rest of the board is not flagged — pointing that out would be handing you the answer.
What happens if I fill it in a way that is right but not the way it was built?
It is accepted. Your filling is checked against the clues, and if every run adds up and no run repeats a digit, it is a solution — there is no stored answer being compared against. That is deliberately different from the usual approach, so that being right is never reported as being wrong.
Is it possible for a puzzle to have two valid answers?
It can happen, and here it does not matter. Because you are checked against the clues rather than against a stored answer, a second valid filling is just another way to solve the same puzzle — both are accepted. The generator does prefer boards that have only one answer and takes a moment to look for them first, but it will not hold up a round over it.
What are the dark squares for?
Nothing is written in them. They separate runs from each other, and some of them hold the clue numbers for the runs starting beside or below them.
Does it need installing or an account?
No. It runs in the browser on a phone, tablet or computer and works offline after the first visit.
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