Fill the grid with the digits 1 to 9. The digits represent the height of the skyscraper in each cell. Each row, column and 3x3-box has exactly one of each digit. The clues along the edges tell you how many skyscrapers you can see from that vantage point. The digits in marked cages are the last digit of the sum of the digits in the cage. In cages there can't be the same digit repeated.