Normal sudoku rules apply. Mod-3 Rows: Each row in the puzzle is a mod-3 line. That is, any set of three horizontally adjacent digits must contain one digit from (1,4,7), one digit from (2,5,8), and one digit from (3,6,9). 159 Indexing: Digits in columns 1, 5, and 9 indicate the column in which the digits 1, 5, or 9 (respectively) appears in that row. (Eg if r4c5 is an 8 then r4c8 is a 5 as the 5 must appear in the 8th column). Renban: Each purple line contains a set of consecutive digits in any order. Little Killer: Digits along the positive diagonal sum to a value that is (strictly) less than 24.