Viewing: Rules

Standard sudoku rules apply. Pairs of cells in corresponding positions in two boxes are shaded. The numbers in these cells should be the same.   […] Read More

This is an extension of consecutive sudoku. Normal sudoku rules apply. A white dot between two cells signifies that the difference between them is 1 (in other words: the two numbers are consecutive). A black dot between two cells signifies that one number is twice as large as the other.   […] Read More

Normal sudoku rules apply. A mark between two cells signifies that the two numbers in the cells are consecutive; the difference between them is 1. (For example: 1 and 2, or 6 and 7.)   […] Read More

In normal X-sudoku puzzles the two diagonals are marked with a thin, gray line. (They might also be shaded, but that's less common.) The lines signify that the sudoku rule of no repeated number also goes for the diagonals. Some puzzles might have more than two lines. The rule is the same: No number can be repeated […] Read More

"Greater than" sudoku have no givens. Instead, there are "greater than" symbols to help you deduce where the different numbers must be. Consider R5C8 in this example: If we follow the "greater than" symbols from cell to cell, we see that all the other numbers in the same box must be bigger. Thus, R5C8 must be […] Read More

In sudoku puzzles with an extra group of cells (marked by shading the cells in the group), the rule about no repeated number also applies to that group. The group is often arranged in a symmetrical pattern, like in the example below […] Read More

A double sudoku is made up of two standard sudoku puzzles overlapping. Each of them cannot be solved on its own; you have to use clues from one puzzle to solve the other, and vice versa […] Read More

Killer sudoku, also called sum sudoku, have no given numbers. Instead, there are sum cages—extra boxes with numbers that are the sums of the numbers inside those boxes. Like the normal sudoku rows, columns and boxes, no number can be repeated in the sum cages. Example: The cage sum 4 can only be the sum of 1+3, not 2+2. […] Read More

Jigsaw sudoku puzzles are just like regular sudoku, except that the boxes have irregular shapes. The irregular boxes fit toghether like the pieces of a jigsaw puzzle—hence the name. Every jigsaw sudoku has boxes with different shapes and a different arrangement of the givens. Figuring out how all this plays together is what makes jigsaw sudoku fun! For […] Read More