Normal sudoku rules apply. Shade some cells using the following rules: cells containing clues in their top left corner must be unshaded (white); the digit in the cell with a “clue” in its top left corner gives the number of white cells orthogonally connected to that clue cell; the clue in the top left corner gives the sum of all the digits in that white area; digits cannot repeat within a white area; each area of white cells is separated by black cells; the black cells are linked to form a continuous orthogonally-connected wall; black cells cannot form a 2x2 square; and all possible clues have been given. Note: the given clues are NOT necessarily located in the leftmost cell of the highest row of that white area.