Daily logic puzzle
Killer Sudoku online, a new sett every midnight.
Killer Sudoku is Sudoku with nothing filled in at the start: the dotted cages carry the sum of the cells inside them and no number repeats within a cage. Ours is called Badgers, it is free, there is no account and no advertising, and a new one appears at midnight.
- a new sett at midnight, six by six on Monday and Tuesday, nine by nine from Wednesday
- exactly one solution, reachable by reasoning, checked by program
- corner, centre and colour marks built in, a two step Check, no red ink while you play
Today's sett. The dotted cages and their totals are the whole clue.
The rules
Three rules, and that is the whole game.
Killer Sudoku is also published as Sumdoku, Sum Doku and Samunamupure. The rules are the same under every name.
- Every row, every column and every block holds each number once. The grid size sets the numbers: six by six uses 1 to 6, nine by nine uses 1 to 9. A block is the small rectangle marked by the thicker line.
- The dotted cages add up. A cage is the group of cells inside one dotted outline, and the small number in its top left corner is what its cells add up to, with no number repeated inside the cage.
- Nothing is filled in at the start: the cages are the whole puzzle, and exactly one arrangement fits.
Our name for it
We call it Badgers.
The puzzle is known as Killer Sudoku. We call ours Badgers because the cages are chambers of a sett and the total is how many badgers live there, and because the rule that no number repeats inside a cage is easier to hold on to when the cage is a room rather than a dotted line.
The rules are untouched. The arithmetic you know carries over: the forty five rule for a row, column or block, the forced combinations in small cages, and the innies and outies across a block boundary.
Where to start
Three ways in.
The archive of past setts is free as well and goes back a year: Badgers archive.
- Play today's sett
The daily puzzle, six by six early in the week and nine by nine from Wednesday, new at midnight.
- How to play Killer Sudoku
The rules with a worked example, the controls and the cage arithmetic worth memorising.
- Practice sets
Sets by difficulty when one sett a day is not enough.
One solution
A program says so, not a person.
Every puzzle we publish has exactly one solution, and it is a program that decides. The generator throws a candidate away unless the solver returns exactly one solution and unless a second solver, restricted to human style reasoning, finishes it without guessing.
You can see the check yourself: the file tests.mjs in the game folder runs it over thirty days in every size. With no starting numbers at all, that check is the only thing standing between a fair puzzle and one that needs a computer.
The controls are the ones serious solvers expect: corner marks, centre marks and nine colours, switched with Z, X, C and V, unlimited undo, and a timer that is a score rather than a limit. Nothing turns red while you play; a mistake shows only through Check.
Questions
Questions about Killer Sudoku.
What is Killer Sudoku?
Sudoku crossed with a sum puzzle. The usual rule holds, each number once per row, column and block, but nothing is given at the start. Instead the grid is divided into dotted cages, each marked with the total of the cells inside it, and no number may repeat within a cage. It is also sold as Sumdoku and Samunamupure.
Is it free here?
Yes. The daily puzzle, the practice sets, the archive going back a year, the hints and the Check are all free, with no account and no advertising. We sell printable puzzle books on the same site, and that is the whole business model.
Can a number repeat inside a cage?
No. That is the rule that makes the totals useful: a cage of two adding to four can only be one and three, never two and two. Without it the sums would rarely force anything.
What is the forty five rule?
Every row, column and block of a nine by nine grid contains 1 to 9 once, so its cells add up to forty five. Compare that with the totals of the cages inside it and the leftover cell, the innie or the outie, is often forced outright. On our six by six grids the same argument gives twenty one.
Do I ever have to guess?
No, and that is checked rather than promised. Every published puzzle was solved by a program restricted to reasoning before it was allowed out. If you are stuck, Hint names the technique and the cage before it fills a cell.
Where can I get more of these on paper?
In the Badgers book: one hundred Killer Sudoku puzzles as a printable PDF in A4 and US Letter, with the solutions at the back. There is a free five puzzle sample to look at first. See the <a href="/puzzle-books/killer-sudoku-book/">Killer Sudoku puzzle book</a>.
Related
More of the same.
One hundred of these on paper, with the solutions at the back: Killer Sudoku puzzle book (PDF, free sample).
All ten daily games are on one page: daily logic games.
Auf Deutsch: Killer Sudoku online spielen.