What is Steampunk?

"Steampunk is a burgeoning subculture that draws on the elaborate aesthetics and romantic worldview of 19th‑century England to envision how things might have looked had a few key technologies been developed further. It conjures a gaslit cityscape filled with steam-powered robots, mechanical computers, ray-gun-toting aeronauts, and monocled mad scientists."

IEEE Spectrum: The Steampunk Contraptors