"No one designed how to design spells," she explains. "That seems to have been stable. But a lot of spells must be purpose-built or at least customized per occasion. If I wanted to - oh - set that little ivy there on fire," she gestures as she flies at a sprig of new ivy, "I'd need to land near it and have a look at just how big and how dry it is and adjust the spell to match. Making a new spell is more or less like that on another scale, but I can't decide that from now on magic in general is going to work by - singing while standing on one's head."