Normal Sudoku rules apply. Each digit inside the grid and its perimeter (rows 0&10 and columns 0&10) represents the height of the Skyscraper in that cell. Taller Skyscrapers hide shorter ones (and ones of the same size). The numbers beside diagonal lines give the number of Skyscraper clues seen in the corresponding directions in rows0&10 and columns 0&10 respectively and all the digits placed there give the number of Skyscrapers seen in the corresponding row or column inside the grid. A clue in a circle is the sum of the digits in the two cells on either side of the clue. [For the avoidance of doubt: the perimeter cells do not obey the rules of sudoku ie they can repeat. So eg along r10 it would be fine for digits to repeat.]