Windex's products are all about cleaning surface. What if a building's windows just as clean as a mirror? Or maybe it just makes the whole building disapear? Anyhow, all we can see is the blue sky.
Before I put my hand on my laptop, I did a lot of sketches and here is one of them. During my research, I found out Windex products are mostly focusing on the idea of cleaning surface, for example the ad that the bird hate windex because windex makes the window so clear that the birds thought it's an open window. So I thought about money laundry, new way to become a monk - they are bald; or show those cute cat slide down from the table etc.
Then I found out since the ad will be place on New York subway, I thought about all the tall buildings with glass widows and the magic show that the magician has a hole in the middle of his body which is an illusion that creative by mirror reflection. So I came out the idea of what is the building is so clean that it can literally reflect the image of the sky.
Here is my design process on computer.