Normal sudoku rules apply. The diagonal from r1c1 to r9c9 acts as a parity mirror. Each cell has the same parity as the cell reflected in the mirror, i.e. if r2c6 is even, r6c2 is also even. The digit in the Nth cell along a teal 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.