Normal sudoku rules apply. Shade some cells such that all shaded cells are orthogonally connected (without creating a 2x2 area) which divides the unshaded cells into blocks of unshaded cells (islands). Each island contains exactly one clue (the small numbers in the grid), and that clue gives the sum of the digits on the island. All clues (except the given 4, whose shading is unknown) are part of the islands. Digits do not repeat on an island. No island is contained within a single 3x3 box, and an island’s cells must have the same sum within each box that island enters. Different visits to a box DO NOT count separately. (Example: A 36 clue island may have cells in 4 boxes that all sum to 9; or 3 boxes with all summing to 12; or 2 boxes with each box's digits summing to 18.)