The Hays Code, a set of moral guidelines for American filmmaking, shaped Hollywood from the 1930s to the 1960s. It aimed to promote wholesome entertainment by prohibiting explicit portrayals of sex, violence, and other controversial topics in movies. Filmmakers had to find creative ways to imply mature themes without showing them directly. This led to the development of new techniques and genres, like innuendo in screwball comedies and symbolism in film noir, that continue to influence cinema today.