How to Play
Killer Sudoku is a logic puzzle based on a 9x9 grid with several prefilled numbers. Each puzzle consists of a 9x9 Sudoku grid containing areas surrounded by the same background color.
The object is to fill all empty squares so that the numbers 1 to 9 appear exactly once in each row, column, and 3x3 box. There is an added twist: You'll also see various shaded cages with a number at the top left. The sum (addition) of the numbers entered into each respective shaded area must be equal to the clue in the area's top-left corner, and no number may be used in the same shaded area more than once. There is only one valid solution to each Sudoku puzzle.
For each day, there are 4 levels of play: Gentle, Moderate (default), Tough, and Diabolical. If you like a tougher puzzle, tap or click on the level or the gear icon, then select the level you wish to play. The application will remember this setting for 30-days (unless you clear your browser data before then).
Killer Sudoku is best experienced in Portrait mode on mobile phones.
Question Mark Icon - Displays the instructions on how to play the puzzle and use the puzzle application.
Information Sign Icon - Displays information about the puzzle itself.
Pencil Icon - This feature mimics playing printed puzzles using a pencil. When activated, you're playing the puzzle with a virtual pencil and all your entries display in a different color so you may differentiate between your guesses and actual answers. You can change this to an actual answer by selecting the cell with the pencil entry, and clicking/tapping on the pencil tool to turn this feature off.
Lightbulb Icon - If you don't know the answer, you can ask the system to provide you the answer by square or reveal the entire puzzle.
Thumbs-Up Icon - If you've entered what you feel is the solution in a particular square or wish to validate everything you've currently entered into the puzzle, you can validate your entries using this feature.
Settings Icon (great) - Access Killer Sudoku specific settings:
Play sound when solved (off by default): When you successfully complete the puzzle, a sound will play.
Check guess when entered (on by default): As you work through the puzzle, the system will give you feedback if the solution is correct or incorrect.
Show timer (on by default): Allows you to time how quickly you solve the puzzle. As you play, use the play/pause button to start/stop the time.
Calendar Icon - If you'd like to play puzzles published in the past, simply choose the date you wish using this feature.