Killer Sudoku

Sudoku, where the dotted shapes add up.

All the rules of sudoku, plus dotted cages whose digits add up to the small number in their corner. The daily board starts empty: the cages are your only clues.

How to play

Each dotted cage adds up to its small corner number.
No cage repeats a digit, and nor does any row, column or box.
The daily starts empty. Pencil marks are how you get in.

Tips and tricks

Learn the fixed pairs. In a two-square cage, 3 is always 1+2, 4 is 1+3, 16 is 7+9 and 17 is 8+9.
And the fixed triples. In a three-square cage, 6 is 1+2+3, 7 is 1+2+4, 23 is 6+8+9 and 24 is 7+8+9.
Use the rule of 45. Every row, column and box adds up to 45. Add the cages that sit wholly inside a box; the difference from 45 is what the leftover squares must hold.
Pencil the cages first. Write the possible digits for the most limited cages, then let ordinary sudoku logic take over.
No repeats inside a cage. A cage of 4 in two squares can't be 2+2, so it must be 1+3.

Where to find it

It takes its turn on the daily page alongside five other rotating games, and the Library always has Easy, Medium and Hard tracks of it. Stuck? A hint costs ink drops, and Inkbloom Plus makes hints unlimited.