Normal sudoku rules apply. Digits in cages must sum to the small clue in the top left corner of the cage. Within cages, digits are “balanced” and the frequencies of the digits are “as equal as possible”. So in cages with sum ≤ 45, each digit occurs at most once, (ie normal killer sudoku). In cages with sum 46 ≤ ... ≤ 90, each digit occurs either once or twice (not never!). Additionally, cells that are a knight's move (in chess) apart must not contain the same digit.