Normal sudoku rules apply. In cages, digits must sum to the small clue in the top left corner of the cage. Every diagonal of length 7,8 or 9 is either modular or unimodular. On modular lines, every set of three sequential digits contains one digit from {147}, one from {258} and one from {369}. On unimodular lines, all digits are from the same class (ie all from {147} or all from {258} or all from {369}).