Normal sudoku rules apply. Yin-Yang: Shade some cells in the grid so that all shaded cells are orthogonally connected, all unshaded cells are orthogonally connected, and no 2×2 region is entirely shaded or entirely unshaded. A shaded cell containing digit x has value x+10; an unshaded cell has value equal to its digit. Region sum lines: Blue lines are divided into segments by box borders. All segments along a single line must have the same sum of values (this sum may differ between lines). Cells connected by a black dot have values, one of which is double the other. Not all dots are necessarily given. The grid is partially covered in fog. Placing correct digits reveals their own cell and may also lift fog elsewhere in the grid. No guessing is required.