Are there fantasy stories where magic is nothing but a highly-advanced technology? And would this blur the line between fantasy and science fiction?
That depends what you think of magic. Magic: "The power of apparently influencing events by using mysterious or supernatural forces." And Technology: "Any sufficiently advanced technology is indistinguishable from magic." And SciFi: "Works of fiction that use scientific discoveries or advanced technology — either actual or imaginary — as part of their plot."So in my opinion in any story where magic is understood/explained and studied upon to the larger extend it kinda becomes a technology. Also because SciFi doesn't have to be scientifically accurate, means that a lot of stories with magic in it could be seen as SciFi too. Mainly stories are seen as SciFi when it has futuristic settings, even if it has nothing to do with science. This is also often why SciFi and Fantasy are categorised together.