"So—I want a world rich in art. How do I get a world rich in art—and rich in different styles of art? Well, in the world I'm familiar with, the way you get the most art is by going to the most cosmopolitan place and looking into all the corners to find the people who are from far-off lands where they do things differently, where it's—different not just like people from across the river but people from across the continent, across the world, people whose traditions grew up around different traditions than mine did—and the idea I had about magic influencing architectural styles by making different things easy or hard than are easy or hard in the world I came from got me thinking—what if I made a dozen or a hundred different little worlds all with their own different kind of magic, and, hmm, either all of them can do travel between worlds but it's hard enough that people will have mostly established what they're like before they figure it out, or only one of them can and that one can connect all the others—and the reason I want different tech levels inside a world is because that means different entire styles of living, which, again, means different art—and of course if there are more worlds to explore after that, I want us to be able to get there eventually, but it doesn't have to be easy, it just has to be doable within my lifetime, I'm not missing out on that." She pauses thoughtfully. "Does 'my lifetime' even have to be a constraint, actually? Can I make myself immortal? On the other hand, if I die again will I be back here with another interesting design project in front of me? That wouldn't be so bad..."

"You probably won't come back here if you die, even if you don't set up your world with an afterlife. You can make everyone immortal, if you want to." She considers for a minute. "Different worlds can be within the same tech level while still having different technology from each other. But if you want one world to be steampunk and one to be Aesthetically Archaic so that you can have steampunk and quasi-archaic art...the short version is 'I don't think so,' and the slightly longer version is that Roses of Villarosa is supposed to be, in and of itself, a single work of art with an approximately coherent aesthetic, and I can absolutely help you defy the spirit of the rules to thumb your nose at that idea, but I can't do that and bend the letter of the rules at the same time."

"I don't necessarily want one world to be one level and a different world to be a different level—I'm thinking of—hmm, perhaps it would be easier with a more concrete example. Let me see."

She does things to clay. There's sort of a little cluster of stylized buildings in the middle of the table, on a little plateau, and then little bridges connecting it to different plateaus, each with its own rough aesthetic—here's a little forest with little houses in the trees, there's a rolling desert with scattered oases and a river and pyramids, there's a mountain range with villages dotting the slopes... but on every plateau, where the bridge from the central plateau meets the local landscape, there's a cluster of buildings in the same style as that central city.

"So there's your Villarosa," she says, pointing at the hub plateau. "And the whole story takes place here, we don't see the rest of the interconnected worlds while I'm busy weaving my tale of love and woe, it's all just there informing the exchange of art and culture. A cosmopolitan city full of travelers from far-off places can have a coherent aesthetic in its own way. I just want that but more. And then within each world," she gestures along the bridge to the mountains, "there's a different people that developed differently, with different magic giving them different capacities and constraints—I don't actually think there should be a single world that's all desert, that's just visual shorthand—but when we get there, we trade, we build, we civilize, now they're part of the empire—and I think, at that point, you can meaningfully say that that world is at the same tech level as we are, even though we haven't chased down and conquered every last nomadic tribe and isolated mountain village. I think it would be genuinely bizarre to have an entire world or set of worlds with no scattered handfuls of people left who haven't moved with the times because they never poke their noses out of their comfortable little valley, or because nobody's sailed past their island yet this century."

"Oh! Yes, if that's what you mean, yes, that's fine."

"Some of them might have remnants bigger than a scattered handful but from the perspective of the story the important parts of every world are the parts that are on a level with Villarosa, whether because Villarosa annexed them or because they got to that level on their own early enough that we didn't try, and perhaps an occasional section of map marked 'here be savages' because we haven't looked any closer than it took to write 'here be savages' on a map. I think that works, doesn't it?"

"Yes, that works."

"Excellent. Then all I have to do is decide how all the magic works. Hmm... I don't suppose you have any examples for me?"

"I have lots of examples! Do you want to give me a general idea of what you'd like your magic system to look like, because these are...diverse."

"I don't know what kind of thing a magic system can be, that's why I want examples! The thing I want is... a lot of very superficially different systems with very different benefits and constraints and usage practices that, once you have the picture of all of them together, are obviously aesthetically coherent as a group. Like a dozen different pieces of an interlocking puzzle where no two pieces are alike but when you fit them all together just right you get a perfect sphere. Except I haven't decided if I want it to be that obvious once we've found them all."

"Ah...hm. That in particular I haven't seen specifically done before...here's some preliminary documentation for examples I've seen," she says, pulling a stack of papers out of thin air. 

She grabs the stack of papers and starts gleefully paging through them, muddy fingers and all.

There are magic systems that people use by doing math, and magic systems that people use by doing art. There are magic systems that people use just by existing. There are magic systems involving rituals, and magic systems involving juggling power and hoping it doesn't blow up on you. 

Hmm hmmm hmmmmmmmmm.

The one that catches her eye is one that has people with inborn magic, different kinds depending what sort of creature they are. "The mechanics speak of humans and elves, but must I divide the population into humans and elves and nothing else, or can I do something more complicated? Are elves necessary at all?"

"You can do something more complicated! 'Human' and 'elf' don't have to strictly correspond to humans or elves at all; if there's one species that's markedly better than another, then the former is the 'elves' and the latter is the 'humans.'"