Normal sudoku rules apply. Digits may not repeat along the indicated diagonals. 5s live in Dutch Flats: All 5s 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. If a digit is in a Circle, exactly that many instances of that digit must appear in Circles. 5s live in Dutch Flats, they don't live in Circles.