This is related to Skyscrapers and ABC Path. Like ABC Path (and unlike Skyscrapers), there can be some blank squares.
Puzzle and Goal
An unsolved puzzle consists of a square with numbers on each side.
The goal is to place numbers in the squares.
The solved grid must satisfy the following conditions:
The number on each side, for each rank, represents the total of the visible buildings.
Shorter buildings cannot be seen behind higher buildings.
Each number must appear exactly once in each rank and diagonal.
Summen-Hochhäuser; Summen-Wolkenkratzer; Sum-Skyline