Killer Sudoku

About Killer Sudoku

Killer Sudoku is sudoku sharpened with arithmetic: dashed cages overlay the grid, each printing the sum of its cells, and no digit repeats within a cage. Nine given digits start you off. Every puzzle is machine-proved to a single solution before it is shown, with a nightly puzzle the same for everyone and endless fresh ones besides. Free in your browser, no ads, no sign-up.

How to play

Fill the grid so every row, column and box holds the digits one through nine, as in ordinary sudoku. The cages add the arithmetic: the small number in a cage’s corner is the sum its cells must reach, and no digit repeats inside a cage. Tap a cell and then a number to write it; the pencil keeps small candidate notes, and conflicts are inked in oxblood the moment they appear.

Controls

• Tap a cell, then a numberWrite a digit
• Pencil, or NToggle candidate notes
• Arrow keysWalk the grid
• Z or BackspaceTake an entry back
• HCounsel fills the chosen cell

Tips

Start with the smallest and largest sums: a two-cell cage of 3 or 17 has only one pair, and 4 or 16 only one apart from it. The two-cell cages are your ladder; write both candidates in pencil and let the rows decide. Remember every box still sums to 45, so a box nearly covered by whole cages betrays its leftover cell.