Killer Sudoku

Killer Sudoku has no given digits. The grid is cut into cages, drawn with dashed lines. The small number in a cage is the sum of its digits, and a cage holds no digit two times.

All the classic rules also apply: each row, each column and each 3 by 3 box must hold the digits 1 to 9 one time.

The server deals a new puzzle for every run and keeps the answer. Every puzzle has one solution, and the cage sums, singles, pairs and the rule of 45 are enough to find it. Your result is your time to the last correct digit.

How to play

• Select Start. The clock starts when the grid shows.
• Add up the cages. Two cells with the sum 3 hold 1 and 2. Three cells with the sum 24 hold 7, 8 and 9.
• A row, a column or a box adds up to 45. Use that to find the one cell of a cage that sticks out of a box.
• Click or tap a cell, then a digit on the number pad. On a keyboard, type the digit.
• A wrong digit turns red and counts as a mistake. The third mistake ends the run, and the run is not saved.
• Select Notes to write candidates in a cell. Select Erase to clear a cell, or Undo to take back the last entry.

What counts in this quiz

• Your result is the time from the moment the grid shows to the moment you enter the last correct digit.
• On the leaderboard, a shorter time ranks higher.
• A run that ends with three mistakes is not saved.

What's not included, and why

• The clock does not stop when you leave the page or change tabs.
• There are no hints.
• A run under 120 seconds is not saved.

Good to know

• Killer Sudoku comes from Japan, where it is called Samunamupure, from the English words sum and number place. The Times of London made it popular in 2005.
• A cage of two cells with the sum 17 holds 8 and 9. A cage of four cells with the sum 10 holds 1, 2, 3 and 4. Such cages are the best places to start.