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. Each horizontal blonde line sums to a 2 digit number. These two digits are at the start and end of its row, in some order. Each vertical brunette line also sums to a 2 digit number. These two digits are at the top and bottom of its column, in some order.