- To play a new puzzle, touch the "New" button and select a difficulty level from the menu. (You need to be online to get a puzzle.) You can also enter a puzzle from another source (eg newspaper)- follow the onscreen instructions.
- Fill in blanks with the Pen (touch the number you want to enter and then the cell).
- To clear a cell, select the "C" key, or enter the same number again. So, if you touch a cell with the incorrect number selected, touch again to clear.
- If you're not 100% sure of a number, you can make a note of it in the cell using the Pencil. To do this, touch the "Pencil" icon to be placed in "Pencil mode".
- You may enter as many pencil marks as you like in each cell.
- Touch the "Pencil" icon again to return to "Pen" mode.
- Touch the Undo icon (yellow arrow) to undo last input. You can undo all the way back to the beginning.
- To remove just one pencilled number in a cell, enter that number again.

Score = Rating + TimeBonus - Accuracy - SolveAids

where:**Rating**= the rating index assigned to each puzzle. This index attempts to measure the difficulty of the puzzle by examining at each stage of the solving process how many cells can be solved by logic relative to the number of unsolved cells. It also looks at what techniques are required to solve those cells. Those that rely on more sophisticated techniques greatly increase the rating index. The current difficulty level (Easy, Medium, Hard, Tough) is only based on the techniques required to solve and you may find that some Easy puzzles have a higher rating than other Medium ones or similarly for Medium/Hard/Tough.**TimeBonus**= extra points for completing the puzzle quickly. In fact, time is still the most important factor determining your score. The time bonus is computed by taking the average time per difficulty level divided by your time and then multiplied by the rating index. For example, the average time for Medium puzzles is currently set at 12 minutes (720 seconds) so if you complete a puzzle with a rating of 1100 in 6 minutes, you will score a time bonus of (720/360 * 1100), ie 2200 which is twice the rating for that puzzle. If you completed the puzzle in 20 minutes (1200 seconds), your time bonus would be (720/1200 * 1100) ie 660.**Accuracy**= the number of errors you make. Errors are only recorded when you enter an incorrect value and then enter a value in another cell. So, if you accidentally enter an incorrect number and immediately correct it, no error will be recorded. For the first error you lose 30 points, for each subsequent error the points lost increases by 10. So you would lose 40 points for the second error and so on. Note that pencil marks do not affect the scoring in any way.**SolveAids**= each time you use a hint or clue or check your input. You lose 40 points for each hint, 50 for each clue and 20 each time you check your input.

- You use the "Solve", "Solve One Cell" or "Possibles" options from the Solve menu.
- You save the puzzle and then reload.
- You do not complete the puzzle.

All puzzles are

You can also enter a puzzle from an external source. After entering all the fixed
numbers, touch the **Done** button.

If you know a puzzle number (perhaps given by a friend), you also play the puzzle by selecting the "Enter Archive Puzzle#".

If the only way to solve a cell is via more advanced solving techniques (as found in Hard and Tough puzzles), then the clue will point you to the cell and say what technique(s) is/are required. This is not as helpful and you may need to resort to the "Solve One Cell" if still stuck.