Normal Sudoku rules apply. Digits 1-4 are pawns, 5's are kings, 8's are rooks. Rooks can 'see' all cells orthogonally until their view is blocked by a pawn. Kings are not allowed to be seen by a rook from outside their own 3x3 box. Digits in grey cells act as clues, (those in column 1 for their row and those in row 1 for their column), indicating how many cells the rook in their row/column can see in total, including cells with pawns blocking its way, but not including the cell with the rook itself.