Puzzles for Brain - Killer Sudoku Book 200 Hard to Expert Puzzles 12x12 (volume 30)

Killer Sudoku is a mix of Sudoku and Kakuro. Your goal is the same as in regular sudoku: fill every row, column and 3x4 region with the numbers 1-12 once. The difference is how you arrive at those numbers. The objective is to fill the grid with numbers from 1 to 12 in a way that the following conditions are met: Each row, column, and nonet contains each number exactly once. The sum of all numbers in a cage must match the small number printed in its corner. No number appears more than once in a cage. (This is the standard rule for killer sudokus, and implies that no cage can include more than 12 cells.)