Normal sudoku rules apply. Digits may not repeat within a cage. Within every 3*3 box (marked by thick black lines), all the killer cages have the same sum. Also, killer cage sums are unique for every 3*3 box i.e if box 1 (top left box) had killer cages each of which sum up to 10, then none of the other boxes can have killer cages with a sum of 10. The killer cage sums are not given and have to be deduced.