He drags out his old boxes of notes and meticulously reads through the indexes on the lids until he comes up with the chart, which spans several pages and neatly lays out the names, costs, and effects of a wide range of wizard spells, grouped into categories by the type of effect and with symbols marking each spell as belonging to one or more technical categories she won't have heard of.

"...I don't know what half of this means but I'm getting the gist, seems mostly sensible."

"Oh good! I am bizarrely proud of the sensibleness of a magic system I had absolutely no part in designing!"

Giggle.

He laughs. "I assure you I would be much prouder if I had. But if I'd designed this system I think it would work very differently."

"Oh, how would you do it?"

"I like how spell design works, but I'd make it a lot harder to accidentally harm yourself casting them - if you try one that's too big you die, I think I mentioned that, and if you mess up the casting process by gesturing imprecisely or slurring an incantation or breaking off in the middle the spell backfires and you end up with a faceful of soot - I really don't see the point in that and would not at all have included those features in a system I was designing from scratch. I'd probably make it more modular and extensible, too, let people install a spell somewhere and then change its parameters or add or remove pieces without having to redo the whole thing, let people build things collaboratively more than wizardry allows for. The thing where one caster can only have one instance of any given static spell active at a time is tidy but it's not very convenient, I'd probably have done something different there too, change the casting process around so casting-reversal pairs can be disambiguated some other way. I do like how you can draw out spell diagrams to keep track of more options than you can fit in your head at once, if anything I think I would've made that a more central part of spellcasting. And this is all assuming I was inventing wizardry, I really don't know what I'd do if I was designing an entire world's magic system from scratch but it might not end up looking very much like Elcenia at all..."

"At what point does it stop being wizardry and start being something else?"

"I think I'd say it stops being wizardry when the thing you're doing when you do magic is no longer 'casting discrete spells using a clearly defined set of actions'. But somebody else might generalize the idea differently. And now of course I'm thinking about how I'd design an entire world's magic system, especially now that I have another world to compare. Are there particular advantages to spherical planets that I'm not thinking of? I'd be inclined to polygons by default, but if spheres work out better somehow..."

"Uh, at least with my world's laws of physics spheres are what happens all by itself, I don't know what's going on with your flat planet at all."

"It's flat, down points inward perpendicular to whatever face you're on, it's kind of unsettling to go over the edge because suddenly you're on a different down... as far as I know, planets are naturally occurring here, but I'm not sure how I'd find out if they weren't..."

"But... how do they naturally occur? In my world all stuff is inclined to go towards other stuff, more so if it's big or nearby, and so planets are stuff that got near other stuff in a ball shape because this is all taking place in a vacuum."

"...Your world is in a vacuum? That sounds uncomfortable."

Giggle. "Air is stuff, it goes toward the planet. It's not very dense stuff, so it's on top of the rocks, mostly. We don't go in the part with vacuum."

"That makes rather more sense. Yeah, okay, I don't know of a meta-rule like that governing the origin and placement of planets. And there aren't parts with vacuum, there's just more air. So your way seems tidier but not necessarily more convenient for the residents, at least not if the residents can fly. I imagine it would be an unpleasant surprise to be on your way up and then suddenly whoops no more breathing for you."

"The air gets thinner as you go up, you can notice that climbing mountains. And it's cold. You'd notice."

"Well, fair enough, but still - as long as I'm designing a hypothetical world, might as well make it so people can breathe most everywhere, right?"

"How does your sun work, in - air?"

"It's a large ball of fire, what about yours?"

"It's basically a ball of fire but I'd expect it to burn any air near it."

"Maybe it burns the air that's near it but the air near that burns somewhat less of its neighbouring air and so forth and then eventually the outlying bits aren't on fire anymore and you have the edge of the sun. I have no idea if that's what's happening, it just seemed vaguely plausible."

"That sounds wrong but I don't know that much about my physics to tell you why."

"Well - you have fire that's not the sun, presumably, and it doesn't burn everything in its path, so there's got to be some limitations to 'fire sets neighbouring air on fire'..."

"The sun is many times bigger than the planet and hotter than any fire you could make on Earth, I think."

"Maybe ours isn't as hot and that's the trick, or maybe fire works differently here the same way down does."