## X Addoku

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# How to Play X Addoku

To solve an X Addoku, use only the numbers from 1 to 9. The numbers in squares linked by a coloured line must add up to the total given in the top left-hand corner of the set of linked squares. No number is repeated in any of these sets of linked squares.Every number from 1 to 9 must also appear in:

- Each of the nine vertical columns
- Each of the nine horizontal rows
- Each of the nine 3x3 boxes
- Each of the two diagonals

The totals given in an X Addoku are like clues. Each is a total to a sum. You have to work out which numbers add up to the total to fill the linked squares. Sounds easy, but each answer has to fit in with the other sums around it.

Use Addoku techniques to help you solve the puzzle. For example, a total of 4 in two squares is a unique Addoku Block. It can’t be 2 + 2 because each block of squares can contain only one of each number. So the two squares can have only 1 or 3, though you don’t know in what order the 1 and 3 go until you look at the other sums around them.

Use the mouse to click up (or down) through the numbers 1 to 9 in each square.

The small black arrows on each side of the square tell you whether you are counting from 1 up to 9 (right arrow) or from 9 down to 1 (left arrow).

Using your keyboard, you can type in up to eight practice numbers below the line at the bottom of each box.

Cross-hatching shows when you have correctly completed each row, column, 3 x 3 box, diagonal and set of squares linked by a coloured line. Any practice numbers disappear.

**Game Options**

PRINT: Click to print the X Addoku puzzle

- Available to YouPlay Premium Members only
- Selected puzzles only

SAVE: Click to save the X Addoku puzzle

- YouPlay Premium Members receive 10 puzzle save slots
- YouPlay Members receive 3 puzzle save slots

PAUSE: Click to halt the timer if you wish to pause during game play

EXIT: Click to return to the Game Selection page

UNDO: Undo your moves one click at a time

CLEAR GRID: Undo all moves and start the X Addoku puzzle again

**Game Features**

TOKEN COUNTER: Displays how many tokens you have won during the game

TIMER: The timer starts as soon as you open the X Addoku puzzle

YouPlay BOOST: Boost your score - multiply your points by working faster and smarter

HINTS: Click to add an extra number to help you solve the X Addoku puzzle

- YouPlay Premium Members receive 5 hints
- YouPlay Members receive 5 hints

# About X Addoku

Addoku is a variant of Sudoku that is sometimes called “Sum Doku” or “Killer Sudoku”. Combining the logic of the traditional puzzle with unique number combinations, Addoku can often be easier to solve than Sudoku, despite its formidable name.

Unlike Sudoku, you don’t begin an Addoku puzzle with any pre-determined numbers. Instead, the grid features individual cells linked by a pre-determined total. These cells must then be filled with non-duplicate numbers from 1 to 9 to match the totals and complete the puzzle.

Scientific studies have recently shown that the focused mental activity used to solve puzzles can help prevent memory loss and degenerative brain disorders such as Alzheimer’s – another reason to get your daily dose of puzzling fun!

The Addoku puzzles featured on YouPlay are presented by *Lovatts Publications*, leaders in the industry for over 25 years. With a reputation for exceptional quality, Lovatts Addoku puzzles will provide you with hours of brain-teasing entertainment.

**Links**

Read the Wikipedia article on Addoku: http://en.wikipedia.org/wiki/Addoku

YouPlay Addoku Tips

1. Single digits can be filled in straight away. Then, look for two-digit sets and work out the possible combinations. For example, the total 3 can only be made up of 1 & 2, and the total 17 can only be made up of 9 & 8. The total of 8, however, could be made up of 1 & 7, 2 & 6 or 3 & 5. It can’t be 4 & 4 because each row, column, block and set can contain the numbers 1 to 9 only once.

2. YouPlay Addoku puzzles have a space at the bottom of each cell where you can type up to eight practice numbers that could be correct.

3. Continue with the three and four-digit sets. Eventually patterns will emerge as you eliminate possibilities.

4. It is useful to remember that the numbers in each row, column and 3 x 3 block add up to a total of 45.