Normal sudoku rules apply. Colour every cell in the grid light or dark. Cells of the same colour are orthogonally connected. Every 2x2 contains both colours. On an “index” line, the digit in the Nth cell along the line (starting from the diamond) indicates the position along the line where the digit N appears. Eg: 3214 would be a valid line with 3 as the diamond; the 1st digit, 3, indicates that the 3rd cell contains a 1, the 2nd cell a 2, and so on. All cells that reference their own position on a line (the digit N is in position N) should be dark. Cells that are not “self-referencing” should be light. Eg for the line 3214 with 3 as the diamond, the 2 and 4 would be dark and the 1 and 3 would be light. Digits separated by a white dot are consecutive and have the same colour. Not all such dots are necessarily given.