Normal sudoku rules apply. The grid is partially covered in fog. Placing correct digits reveals clues in the surrounding 3x3 area. No guessing is required. Shade some cell such that all shaded cells are orthogonally connected, all unshaded cells are orthogonally connected and each 2x2 area contains shaded and unshaded cells. The value of an unshaded cell is its digit. The value of a shaded cell is double its digit. Values along an arrow sum to the value of the attached circle. Arrows don't overlap.