Normal sudoku rules apply. Circle a digit in each row, column, and box. Each circled digit must be different. Shade some cells, such that within any row, column, or box, the number of shaded cells is equal to the circled digit. A digit in a diamond is not circled, and equals the sum of the circled digits in its row and column. Shaded digits within a cage sum to the value given in the top left of the cage.