Sudoku Rules:

The most common type of Sudoku consists of 81 fields which are ordered in 9 sub-squares with 9 fields each. Every row and column has 9 fields. In order to complete a Sudoku riddle, the numbers from 1 to 9 have to be placed exactly once within the fields so that the three following rules are not broken:
As soon as all different numbers are placed exactly once in each row, column and sub-square, the riddle is completed.
Depending on the degree of difficulty a certain amount of numbers is given when a game is started.

Generalized Sudoku Rules:

This principle can be generalized by describing the game as a square of n*n fields divided into n sub-squares of sqrt(n)*sqrt(n) fields. Only numbers with an integer square root (4,9,16,25,...) can be chosen for Sudoku. There are n different symbols available to be placed inside the fields. Basically there is one rule to be satisfied: Do not place two equal symbols in one entity, where entities are rows, columns and sub-squares. This translates to three simple rules: