Normal sudoku rules apply. Placing correct digits may clear some fog. Digits separated by an X sum to 10, digits separated by a V sum to 5. Purple (Howling Mad) lines indicate a sequence of digits where no other specified line type could go: Renban: Consecutive non-repeating digits; Nabner: Non-consecutive non-repeating digits; Parity: Alternating even/odd; Entropy: Every 3 digits has a [1,2,3], [4,5,6], and [7,8,9] digit; Modular: Every 3 digits has a [1,4,7], [2,5,8], and [3,6,9] digit; Dutch Whisper: Adjacent digits differ by at least 4; Region Sum: Box borders divide lines into segments with the same sum. Howling Mad lines are always three cells long and are always either strictly vertical or strictly horizontal. Lines cannot overlap each other. No set of digits appears on more than one line. For example, if one line contains 1, 2, and 4, no other line can contain all three of those digits. Given those rules, no further lines are possible.