# Documentation

**Documentation Topics:**

## Rules of Su Doku

**Fill in the grid so that every row, every column and every sub-quadrangle contains
exactly one instance of each available symbol (for example, the numbers 1 through
9). **

Su Doku is a symbolic puzzle. The goal is to populate a grid (for example a 9×9 grid) with instances of a range of valid symbols (for example, the numbers 1 through 9, or the letters A through I). The grid is sub-divided into quadrangles (a 9×9 grid is made up of 3×3 (nine) such quadrangles, each containing 3×3 cells), and is pre-populated with random distributions of occurances of these symbols (typically between 22 and 36 in a 9×9 grid). Your goal is to complete the grid, adhering to three simple rules:

- Each column in the grid may contain only one instance of every permissable symbol. (I.e. each column must contain one, and only one, '5' cell).
- Each row in the grid may contain only one instance of every permissable symbol. (I.e. each row must contain exactly one '1' cell).
- Each quadrangle in the grid may contain only one instance of every permissable symbol. (I.e. each quadrangle must contain exactly one '1' cell, one '2' cell, one '3' cell etc. through '9'.)

Here is an example of a Su Doku puzzle, generated by SuDoku Pro:

SuDoku Pro currently supports the following puzzle sizes:

- 4×4 puzzles with numeric or letter symbols
- 9×9 puzzles with numeric or letter symbols
- 16×16 puzzles with letter symbols
- 25×25 puzzles with letter symbols