Normal sudoku rules apply. Each turquoise line is an Index Line, i.e. the digit in the Nth cell along such a line (starting from the diamond) indicates the position along the line where the digit N appears. For example, if a diamond cell contains a 3, the third cell along that line must have a 1. The yellow lines are Nabner Lines, i.e. on such a line there may not be consecutive or repeated digits. For example, if a 5 lies on a Nabner line, this line may not contain another 5 and neither a 4 nor a 6.