"That's interesting. If not obviously practically relevant." She writes it down anyway.

"Mostly it's just interesting. I wonder if I could program a hard shine to leave the Earth's atmosphere, accelerate to--not lightspeed, that would destroy any cameras or whatever, but use them as space probes."

"Maybe! Earth is your planet, I assume? What's a camera?"

"Earth is my planet! A camera is a machine that points a lens at something and creates an image of what it sees."

"Huh. You can sort of do that with shines. Shines can go through each other when they aren't this kind, and they can be any color a patch of light can be. So if you get a bunch of stacks of them in different color, and then put the stacks in a grid, and program them all to change where they are in the stack based on what they see on the surface they're on, you can copy a picture fuzzily onto shines. But shines can only see what they're actually on, not things that are farther away. I don't think I've heard of them being used to match focused light from somewhere else, but that could probably work too."

"I don't actually recall how exactly it works. It involves using lenses to make the light bouncing off something to show up as itself and not just random ambient light, I'm pretty sure."

"I don't know much about lenses except that they're useful for making small shines."

"They are also useful for a wide variety of other things involving making light go where you want it."

"That would seem to follow, yes."

"Yeah. Not really my area, though, you might think that my powers would make me more interested in how light works in general but until now it hasn't really been relevant."

"I'm a reasonably devoted student of meteorology," Marie volunteers. "...Oh, right, we didn't mention. I have powers too, I do wind."

"Do wind? Do what with wind?"

"I...make it exist. Or not exist. Or go here instead of there or make loops or whatever. I'm telekinetic with air, basically."

"That sounds handy. Unfortunately there's no obvious servant synergy."

"I don't know enough about aerodynamics to help with the design there, but I'll shine-ify a sail for you."

"I don't know a lot about aerodynamics either, you're going to have to design anything you want and figure out how to describe it coherently," Helen informs Marie.

"Sure, sure," she says, waving a hand. "Oh, hey, Bar, is this book originally published in English? And if so how much does it cost?"

Spanish, but there is an English translation available. $24.

"Hold the door for me so I can fetch my wallet?" she asks Helen. "I probably wasn't going to finish this while we were here anyway but especially not while I'm doing sketches of aerodynamic structures."

"Yeah, okay." She leaves off writing the practice programs while she's holding the door but keeps reading the book and generating barriers to be shined.

And Lu continues pulling them out of the air in batches, between writing lines of a test three-dimensional program.

Marie nips out and fetches her money, and pays for the book. She then solicits a pencil and some blank paper to design things with.

Bar, as always, obliges.

Convenient aerodynamic object design. Fun. Or at least the end results will be.