Normal sudoku rules apply. Yin Yang: Shade some cells such that all shaded cells are orthogonally connected, all unshaded cells are orthogonally connected, and no 2x2 area is fully shaded or fully unshaded. Small numbers in the corners of cells are ‘internal X-Sum’ clues: The digit in a cell with a clue gives the total number of cells (including itself) of the same shading as itself seen in all horizontal/vertical directions combined (cells of the opposite shading block the vision). Those cells sum to the number given by the clue. Digits may repeat within a sum if allowed by other rules.