Normal sudoku rules apply. Every 5 in the grid must have a 1 directly above it or a 9 directly below it. It may have both, but it doesn't need both. The grid is covered in fog. Entering correct digits might clear fog somewhere in the grid. A stick always has a lower total (the sum of its digits) than any stick which lies on top of it. Sticks that aren't grey have an additional rule: A yellow ENTROPIC stick must contain one low digit (1, 2 or 3), one medium digit (4, 5 or 6), and one high digit (7, 8 or 9.); a teal MODULAR stick must contain one digit from each of the sets (1,4,7), (2,5,8), and (3,6,9); a pink RENBAN stick must contain a set of consecutive digits – these can be arranged in any order; along an orange DUTCH WHISPER stick, adjacent digits must have a difference of at least 4; along a red PARITY STICK, digits must alternate between odd and even.