Digits on an arrow sum to the digit in the attached circle. (Digits can repeat along arrows if allowed by other rules). In cages, digits must sum to the small clue in the top left corner of the cage. Digits cannot repeat within a cage. This puzzle is solved in two stages: 1. Normal 9x9 sudoku rules DO NOT apply. Solve each 3x3 box within the grid independently (so ignoring the rest of the grid). ie Three digits (selected from 1 to 9) need to be placed in each row/column of that 3x3 box once each. 2. Erase all digits within the grid whose box number does not match their row number (eg you'll keep the digits in r4c1c2c3 within box 4). Then solve the puzzle as a regular killer arrow sudoku using the remaining digits as givens (ie normal sudoku rules will apply at this point).