Normal sudoku rules apply. Cells separated by a white dot must contain consecutive digits. Cells separated by a black dot must contain digits in the ratio 1:2. Not all dots are given. The red line is a palindrome for which the start cell and end cell must be determined. The line must read the same in either direction. Neighbouring digits along the line cannot be further apart in value than two steps (so a 5 would have to be next to 3,4,5,6 or 7). For this purpose 1 and 9 are considered to be consecutive. (E.g., a 1 can have the digits 8, 9, 1, 2 or 3 as neighbours along the line.)