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 will have exactly one of each digit. The green and yellow cells around the grid tell you whether the number of skyscrapers you can see from that vantage point is even or odd. Yellow cells mean that you can see an odd number, green cells mean that you can see an even number.