As an icon of the complex, 30 Rockefeller Plaza's architecture, with its limestone facade and Gothic-inspired four-leafed spandrels, influenced the design of the rest of the complex. The design of 30 Rockefeller Center was affected greatly by the 1916 Zoning Resolution, which restricted the height that the street-side exterior walls of New York City buildings could rise before they needed to incorporate setbacks that recessed the buildings' exterior walls away from the streets. Hood also created a guideline that all of the office space in the complex would be no more than from a window, which was the maximum distance that sunlight could permeate the windows of a building at New York City's latitude. Although the RCA Building was recessed so far into the block that it could have simply risen as a slab without any setbacks, Hood decided to include setbacks anyway because they represented "a sense of future, a sense of energy, a sense of purpose," according to the architecture expert Alan Balfour. The setbacks on the northern and southern sides of 30 Rockefeller Plaza allow the building to comply with Hood's 27-foot guideline, but the eastern elevation's setbacks are merely for show, according to Balfour.