Killer Sudoku by Sudoku.com

About Killer Sudoku by Sudoku.com

Killer sudoku keeps the rules of classic sudoku, every row, column and 3x3 box holding the digits 1 to 9 once, and adds cages. Each cell sits inside a cage marked with dotted lines, and the small number in the cage's top left corner is the sum its digits must reach. Digits cannot repeat within a cage either. Harder grids start with few or no digits, so the cage sums carry most of the logic.

This app comes from Easybrain, the maker of Sudoku.com, and plays the same way: you pick a cell and a digit, can switch on Notes for candidates, undo and erase, and use a few hints. A game ends after three mistakes, and a score and a timer run above the grid. Games come at several difficulty levels, and the app says it is meant to make killer sudoku approachable for players of every level.

The Daily Challenges give one puzzle for each date and win unique trophies, and seasonal events award medals. The app is free with ads.

How to play Killer Sudoku by Sudoku.com

1. Open the app and choose today's Daily Challenge.
2. Read the cage sums: the digits in each dotted cage must add up to the number in its corner.
3. Fill the grid so each row, column and 3x3 box has 1 to 9 once, with no repeats inside a cage.
4. Use Notes to pencil in candidates; three mistakes end the game.
5. Complete the grid to mark the day on the calendar and work toward the month's trophy.

Tips

• Learn the fixed combinations: a two-cell cage of 3 is always 1 and 2, of 17 always 8 and 9.
• Each row, column and box adds up to 45; subtract the cages that fit inside one to find a single leftover cell.
• Note the possible digits for small cages first; they narrow everything around them.

Questions