## Rules

## Sudoku

The rules are simple, but game play is challenging.

### The game board

The game board is made up nine columns and nine rows, subdivided into nine 3x3 sub-sections, for a total of 81 squares.

### Getting started

Each game board starts out with some cells already filled in. Generally, easier puzzles start with more numbers, harder puzzles start with fewer.

Your job is to fill in the boxes so each of the nine rows, nine columns, and nine 3x3 blocks contains the numbers 1 to 9 with no duplicates.

## Basic strategy

Below we're trying to solve for the cell marked in pink. Its 3x3 block has three empty cells, and it's missing the numbers 1, 7 and 8, so we know the pink cell must contain one of those numbers, and no others.

A little observation shows that the rows above and below the pink cell already contain the number 1:

Therefore, the pink cell must contain the number 1. The numbers 7 and 8 must go in the two remaining cells. Can you figure out where?

Because the top row already contained a 7 in the far right cell, we know that row cannot contain another 7. Therefore, the 8 is in the top pink cell and, by process of elimination, the 7 goes in the bottom cell:

Now you know the top left cell must contain the number 5, since it's the only number missing from that row! Not too hard, right?

## A completed game

Note that no cell, row or 3x3 block contains a duplicate entry:

### Never guess!

Sudoku is a game that works though the careful, thoughtful process of elimination. Guessing will lead to mistakes, and the goal of sudoku is to avoid mistakes at all costs!

### Errors

Errors are marked in red. In the screens below, the number 5 was erroneously placed in the sixth column / fifth row. This caused duplicates in that cell's row, column and 3x3 block, as shown below:

### Notes

The Notes feature allows you to jot down the numbers you think might go in any given cell without committing to an entry. This feature is particularly helpful for more challenging games.

### Hints

Although "hardcore" sudoku players will never use a hint, you can use this feature while you're learning. Simply press and hold any cell and a hint will appear. **Note**: hints add a penalty of 15 seconds to your overall time.

### Game Play

Here is a sped up (20x) video of Sue Doku being played on Level 1.

### Clearing a cell

To clear an entry or note from any cell simply swipe in any direction. **Note**: because hints carry a 15-second penalty, they cannot be cleared.

### That's about it!

As you get better, the time it takes you to complete each puzzle will improve. You can view your best and average times on the stats screen.

There are many websites and books that offer advanced sudoku strategies, but the rules above will get you started!

We hope you enjoy Sue Doku! If you have any questions or comments, please contact us.