Normal sudoku rules apply. Each 3x3 box contains a circled digit which is equal to the addend of that box. The addend applies to all cells of the box it lies within. The value of each cell is equal to the digit placed in the cell added to the addend of its box. The nine circled cells contain a different digit. Cells separated by a black dot have values in which one is double the other. Not all black dots are necessarily given. Box borders divide the blue lines into segments whose values have the same sum. Different lines may have different sums.