Sudoku 9 x 9

Sudoku (also known as "Number Place") is a placement puzzle. The puzzle is most frequently a 9 x 9 grid made up of 3 x 3 subgrids (called "regions"). Some cells already contain numbers, known as "givens". The goal is to fill in the empty cells, one number in each, so that each column, row, and region contains the numbers 1 through 9 exactly once. Each number in the solution therefore occurs only once in each of three "directions", hence the "single numbers" implied by the puzzle's name.

In some sudokus main diagonals also contain the digits 1 through 9. This variant is called "Sudoku X", "Diagonal Sudoku" or "Kokonotsu". Use the check box Diagonals for such sudokus.

"Argyle Sudoku" contains additional diagonals; every marked diagonal line contains each digit not more than once. The argyle pattern is derived from the tartan of Clan Campbell, in eastern Scotland.

Also the puzzle may contain the regions of random (irregular) shape; this variant is called "Jigsaw", "Geometry Sudoku" ("Geometry Number Place"), "Irregular Sudoku" or "Kikagaku Nanpure":

"Godoku" (also known as "Wordoku") is similar to sudoku, but uses letters instead of numbers. Once the grid is complete, the hidden word may be revealed.

In "Asterisk Sudoku" there is an additional area, shown on the grid by shading nine specially selected cells. Those nine cells must also contain 1 to 9.

"Girandola" is an ordinary sudoku with one extra group of cells. This group must also contain digits 1 through 9. (Girandola is a kind of revolving firework.)

"Center Dot" is a variant of sudoku, where central cells of each region form an extra region. This region must contain digits 1 through 9.

Sudoku may contain additional four regions 3 x 3. This format was first introduced in the Dutch newspaper "NRC Handelsblad" by Peter Ritmeester. It is called "Windoku" ("Four-Box Sudoku", "Hyper Sudoku").

"Sudoku-DG" (also known as "Offset Sudoku") contains 9 disjoint groups in the puzzle, one for each relative box position. Each group has a distinct color. The group of 9 cells with the same color must also contain digits 1 through 9.

In "Anti-Knight Sudoku" all cells at a chess knight move (at a distance of 2 by 1) must hold different numbers.

In "Anti Diagonal Sudoku" each diagonal has at most three different digits.

In "Killer Sudoku", sub-regions have specified sums, and no number can be repeated within a region. This variant also called "Sums Sudoku" ("Sums Number Place").

"Greater Than Sudoku" is the variation of the original sudoku. In addition, greater than or less than signs (">" or "<") in the walls indicate that one cell's number is greater than or less than an adjacent cell's number. Also called "Compdoku".

"Even-Odd Sudoku": fill in the grid so that every row, every column, and every 3 x 3 box contains the digits 1 through 9. White cells must contain odd digits, gray cells must contain even digits.

In "Consecutive Sudoku" (or "1-away Disallowed Number Place"), all the places where orthogonally adjacent cells are consecutive numbers have been specially marked.

"Kropki Sudoku" (from Polish, literally "dots"; also known as "Dots Sudoku") is the variation of the original sudoku. If absolute difference between two digits in neighboring cells equals 1, then they are separated by a white dot. If the digit is a half of digit in the neighboring cell, then they are separated by black dot. The dot between 1 and 2 can be either white or black.

"Sukaku" ("Suuji Kakure"; also known as "Pencilmark Sudoku") has 81 groups of digits in a 9 x 9 grid. Like a standard sudoku, the puzzle must be completed in such a way that each row, each column and each 3 x 3 box contains digits 1 through 9. Only the candidates shown in the grid can be used.

"Chain Sudoku" (also known as "Strimko") consists of a group of circles arranged in a square grid and containing given clues in various places. The object is to fill all empty circles so that the digits appear exactly once in each row, column and chain.

"Frame Sudoku" (also known as "Outside Sum Sudoku") consists of an empty grid. Numbers in the outside frame equal the sum of the first three numbers in the corresponding row or column in the given direction.