Try to find the skyscrapers hidden in the grid. The buildings are of various heights (1<2<3...) and the numbers above the frame indicate the different heights of each skyscraper. Each skyscraper appears only once in every row and column. The numbers around the grid tell you how many buildings you can see from that vantage point in the corresponding row or column. Keep in mind that higher buildings hide smaller ones.
In this variant there is also an empty square in every row and column, that can't hide a building and can't be seen behind a building. For this empty square you can put an X or leave it empty.