The grid is partially covered in fog. Placing correct digits will clear the fog, possibly revealing more clues. No guessing is required. Each row, column, and region contains the digits 1–9 exactly once each. A region is an orthogonally connected collection of cells, and regions are to be determined. The digit in a cell containing an arrow indicates the number of region borders in that direction. (If there is more than one arrow, the number of borders is the same in each direction eg a 4 in the cell with two arrows pointing East and North would indicate that there were 4 borders to the East AND 4 borders to the North). The outer edges of the grid do not count as borders. A digit in a circle equals the total number of cells seen horizontally and vertically that are in the same region as the digit, including itself. Borders obstruct vision.