Killer Sudoku: Number Puzzle

Killer sudoku: cages that add up, daily puzzles, hints that explain.

A sudoku grid with dashed cages drawn over it, each carrying the total its squares must add up to. Easy boards give you around twenty numbers to build on; expert gives you nothing but the cages. Every puzzle has exactly one answer, its difficulty is graded by the hardest technique it needs, and a hint names the rule instead of just filling in the square.