Normal sudoku rules apply. Cages may not include repeated digits. Each cage should be treated as a “building” with a height equal to the sum of the digits in the cage. (Eg a cage containing the digits 2, 6 & 8 would equate to a building of height 16.) Cells outside of cages are completely ignored for the purposes of the clues outside the grid. The clues outside the grid give the number of buildings that can be "seen" along that row or column, whereby (1) taller buildings obscure shorter buildings and (2) in a row/column with a clue outside the grid, there can never be two buildings of the same height. Note that a row/column without a clue does not necessarily have repeated building heights but may do.