Bubble Sudoku › Guides
Is Sudoku Math?
No. You never add, subtract, multiply, or divide in sudoku. The numbers on the grid are only labels. Any nine different symbols work just as well, and Bubble Sudoku uses nine colors.
What sudoku asks you to do
Sudoku has one rule: every row, column, and block holds each symbol exactly once. Solving means working out where each symbol can go and ruling out where it cannot.
Take a row that already holds eight colors. The empty cell must take the ninth. You found it by noticing what was missing, not by doing a sum. Every sudoku technique, up to the hardest ones, works the same way. Each one is a piece of logic about where a symbol can and cannot go. The Techniques pages show all fifteen, animated on real boards.
Here is a quick test. If the numbers meant anything, 9 would be worth more than 1. In sudoku it never is. You could swap every 3 on a board for a 7, and every 7 for a 3, and the puzzle would work exactly as before.
So why does sudoku use numbers?
Mostly history. The puzzle first appeared in 1979 in a Dell puzzle magazine in the United States, under the name Number Place. It is usually credited to Howard Garns, a retired architect from Indiana. In 1984 the Japanese publisher Nikoli brought it to Japan with a name that translates as “the digits must be single,” later shortened to Sudoku. It spread around the world after The Times in London began printing it in 2004.
The digits one to nine were simply a set of nine different symbols that every reader already knew. They could have been anything.
Where math does come in
Mathematicians study sudoku for their own reasons, and none of it is needed to play.
- They have counted every possible finished 9×9 grid. There are 6,670,903,752,021,072,936,960 of them, about 6.67 sextillion.
- A paper published in 2014 by Gary McGuire, Bastian Tugemann, and Gilles Civario used a huge computer search to show that a sudoku with only one answer needs at least seventeen starting clues.
- Mathematicians also describe sudoku as a coloring problem. Think of each cell as a point, and connect every pair of cells that share a row, column, or block. Now give every point one of nine colors so that no two connected points match. That is a finished sudoku, and it is exactly what you do on a Bubble Sudoku board.
Why play with colors
If numbers on a grid remind you of math class, colors take that feeling away. The logic stays the same. You look for the missing color in a row instead of the missing number, and a finished row is nine different colors side by side.
Bubble Sudoku has four levels, a daily puzzle that is the same board for every player, and hints that walk you through each technique on your own board. For players who find some colors hard to tell apart, the Colorblind Symbols setting adds a distinct shape to every color. Read more about color sudoku, or start with the rules.
Questions
Do you need to be good at math to play sudoku?
No. You need patience and the habit of checking rows, columns, and blocks. No arithmetic is used at any level, from the easiest puzzle to the hardest.
Can sudoku use letters or shapes instead of numbers?
Yes. Sudoku only ever asks whether two symbols are the same or different, so any nine different symbols make a working puzzle. Letters, shapes, and colors all work.
Is color sudoku harder than number sudoku?
It is the same puzzle, with the same rules and the same techniques. Whether colors feel easier depends on the player, and the quickest way to find out is to try a board.
Try sudoku without numbers
Nine colors, the same logic, and no math anywhere. Free in your browser, with no account.