Work Text:
Summer had settled over Salt Lake City by the middle of 2010, bringing with it dry heat, cloudless skies, and the sort of afternoons that made staying inside Anti-Entropy's air-conditioned base sound like a very good idea.
Things inside had changed somewhat since January as well.
Kiana Kaslana was no longer the strange white-haired girl that people stopped to look at whenever she wandered through the engineering wing. By now, most of the base had gotten used to seeing her carrying various electronic parts around, asking questions no ten-year-old had any business asking, or trailing after Tesla on whatever project caught her attention that week.
The occasional explosions had stopped attracting much attention too, which Tesla liked to think said more about Anti-Entropy than either one of them.
On that particular afternoon, however, Tesla wasn't causing any explosions.
Rather, she was asleep on her workbench.
Her latest mecha prototype had spent most of the previous evening finding increasingly creative ways to malfunction, until Tesla eventually decided that resting her head for a few minutes couldn't hurt.
Several hours later, something poked her cheek.
"Doctor?" Kiana called out when Tesla didn't move. "Where are the ceramic sleeves?"
"... Cabinet," Tesla mumbled into her arms.
"Which one?"
"Left."
"I checked."
"Other left."
There was a short silence before Kiana replied, "Doctor, there are six cabinets."
Tesla groaned. Why did she teach the kid to ask questions? "The one next to the parts rack. Blue box."
"It's locked."
Right. Tesla vaguely remembered doing that after Kiana discovered what capacitors could do when mistreated. "The key's in my coat."
"Where's your coat?"
That... was a very good question.
Tesla finally opened one eye, finding the little girl standing beside the workbench and looking at her expectantly. Tesla considered the problem for a few seconds before deciding that it belonged to her future self. "I'll find it later."
"But I need the ceramic sleeves now," Kiana complained, poking her cheek again.
That did it.
Tesla caught her around the waist and pulled her closer before the girl could get away, ignoring the startled noise as Kiana immediately started squirming in her grasp.
"Doctor, what are you doing?!"
Tesla gave the matter the amount of thought it deserved.
Small. Warm. Soft. Fluffy. Those were all the important qualifications.
"Plushie," she concluded, tightening her hold and burying her face against Kiana's hair.
"I'm not a plushie!"
Tesla disagreed. And, more importantly, she was comfortable once again.
"Doctor..." Kiana whined, still trying to wriggle free. "Coralie's waiting…!"
Kiana continued squirming and complaining, but Tesla had already closed her eyes. Whatever the kid was building could wait another five minutes.
Coralie could wait too. She was perfectly capable of entertaining herself for a while. She'd probably find some snacks, poke around whatever Kiana had been working on, or wander off to bother Einstein until Tesla eventually got up.
That last thought took a few seconds to work its way through Tesla's exhausted brain.
Then she remembered the small detail that Kiana and Coralie weren't even supposed to know each other yet, and finally processed that they were apparently doing something unsupervised that required ceramic sleeves of all things.
Her eyes snapped open.
.
A few minutes later, Tesla entered the auxiliary laboratory through an access door with Kiana following closely behind.
Like most of the engineering laboratories in the base, the place was less a single room and more a small collection of them. The main work area was large enough for several workbenches and pieces of testing equipment, with smaller adjoining rooms set aside for things like storage, calibration, and whatever else the current occupants needed. This particular lab wasn't assigned to anyone at the moment, so most of those rooms were filled with backup equipment and other supplies that had nowhere better to go.
That also meant it was effectively Kiana's playground more often than not.
The ceramic sleeves she asked for, however, remained locked away.
More importantly, given current circumstances, Tesla had forbidden Kiana from building anything until she figured out what exactly was going on. No wiring, no soldering, and definitely no testing anything with Coralie involved.
Kiana had taken the news about as well as expected, and was still pouting.
As they walked into the main area, a casually dressed Coralie was sitting on a stool by one of the workbenches with an open bag of snacks in her lap, as if she were lounging about in a living room rather than what was ostensibly a workplace.
"Oh, there you are," the small dog girl greeted in a flat tone before eating another piece, her expression remaining perfectly straight even as her tail gave a content little wag behind the stool.
"Doctor won't give us the ceramic sleeves," Kiana complained.
Coralie considered that. "We could use the other insulation."
"No, you couldn't," Tesla immediately cut in. "Because you're not building anything."
That earned her a questioning look from Coralie and an even bigger pout from Kiana.
Wonderful.
Tesla walked closer to the workbench and found several sheets of paper spread across it, covered in rough diagrams, arrows, and enough notes to make it obvious the girls hadn't spent the last few hours discussing the weather.
"What exactly are you two planning?" she asked them, already dreading the impending answer.
"We were talking about robots," Kiana replied in an almost sullen tone. "Coralie said having one big power thing is bad because everything stops if it breaks."
"A centralized power system," Coralie clarified. "We thought smaller independent units might work better for some designs."
"And then if one arm breaks, the other one can still move!" Kiana added.
Tesla glanced down at the diagrams. Distributed power wasn't exactly revolutionary, but the way they were applying it could actually be rather cost-effective if saved for specialized units rather than mass implementation...
No. Not the point.
"And then we started thinking about the controls," Coralie continued when Tesla said nothing. "If each section already has its own power supply, giving them local controllers would reduce how much the central system has to handle."
Tesla's eyes moved to another page before she could stop herself. "You'd need them synchronized, or the whole thing would go straight to the ground the moment if just two joints disagreed."
Kiana nodded quickly. "That's what we were trying to figure out!"
Tesla paused before she could inadvertently share ideas.
Shit.
She straightened and deliberately looked away from the papers. "Still not building it."
Kiana's pout returned. Coralie simply ate another snack, though the wagging of her tail slowing down suggested she wasn't nearly as indifferent to the discussion as her face made her look.
Tesla narrowed her eyes on both of them. "When did you two even meet?"
"This morning," Coralie replied.
Tesla looked at the diagrams again. Then at Kiana. Then at Coralie.
They had managed to get this far in just a few hours. Tesla had a feeling she shouldn't think about it too hard.
"Stay here and don't get started on anything. I need to make a call," Tesla said as she stepped away from the workbench. She stopped just long enough to point at both girls. "And I mean it. Don't build anything."
Kiana immediately opened her mouth.
"Anything," Tesla stressed.
Kiana closed it again.
Tesla considered going back into her own laboratory for the call, but that would mean putting some extra distance between herself and those girls, and that sounded suspiciously like tempting fate. Instead, she headed for one of the smaller rooms adjoining the auxiliary lab, a storage area full of backup electronics and spare equipment.
The walls were probably insulated well enough for Tesla's purposes. So long as she didn't shout too much, at least.
She pulled the door shut behind herself and took out her phone.
.
"So you left Coralie alone with Kiana because you thought it would be amusing?" Tesla growled into the phone.
"That isn't exactly how I'd phrase it," Einstein replied calmly. "You told me you wanted to wait until Kiana was more comfortable at Anti-Entropy before introducing them to each other. I simply believed it was time."
"That was just one of the conditions, Mophead!" Tesla snapped. "The other was doing it somewhere controlled, preferably with one of us actually there to stop them from getting ideas!"
Tesla had been perfectly aware that keeping the two girls apart forever would be both pointless and probably impossible. Coralie already spent plenty of time around Anti-Entropy's laboratories, while Kiana had taken to engineering with enough enthusiasm that their paths were bound to cross sooner or later.
The idea, however, had been to see how the two got along somewhere that didn't contain enough spare equipment to start an arms race with Schicksal, because Tesla damn well knew that things simply happened when one placed two geniuses in the same room with no clear restrictions, let alone young ones.
"They're in an auxiliary laboratory," Einstein pointed out. "I would consider that a fairly controlled environment."
Tesla nearly threw the phone at a wall. "Do I need to remind you that there was nobody supervising them?!"
"There are security systems," Einstein argued.
"Security systems aren't going to tell Kiana that testing explosives indoors is a bad idea!" Tesla shot back.
Einstein hummed. "Then perhaps you shouldn't have taught her to do so?"
Tesla paused for a moment.
"... That's not the point and you know it."
She could practically hear Einstein smiling on the other end.
"The point," Tesla continued before the woman could come up with another argument, "is that they met only a few hours ago and they're already working out distributed power and control systems for a mecha!"
"That sounds to me like they got along."
"Too well!"
That was exactly the problem. Tesla hadn't been worried about them disliking each other. She'd been worried they would click like this. Kiana absorbed engineering frighteningly fast once the logic made sense to her, and Coralie had never suffered from a shortage of ideas. Putting them together meant they could skip the awkward introductions and go straight into designing machinery recklessly.
Einstein remained infuriatingly unbothered. "Then I suppose there's nothing to worry about."
Tesla had no idea whether Einstein was ignoring everything she said or baiting her on purpose.
Oh, who was she kidding, that was absolutely bait.
"Mophead," Tesla began slowly, "if those two end up building Arahato 2.0, it'll be your fault."
There was a brief pause before Einstein replied, "I imagine Joachim would be rather pleased with that result."
Tesla closed her eyes. The worst part was that she couldn't even dismiss that outright. Joachim would object to the circumstances of building a giant robot with no prior approval and following proper protocols, obviously. He liked to pretend he was a responsible adult.
He would also absolutely want to see the test run. Or straight up pilot it.
"You're supposed to be the sensible one here," Tesla muttered, rubbing at her forehead. "I'm the one who teaches children that blowing up spare circuitry counts as a learning experience. If you start throwing them into laboratories full of spare parts together because you think the result might be funny, where exactly does that leave us?"
"Perhaps with a more balanced division of responsibilities?"
"No," Tesla snapped. "It leaves me telling Kiana she's not allowed to build anything even though it sounds fun! Do you have any idea how wrong that feels?!"
Einstein actually laughed.
Tesla felt her eye twitch. "Go choke on your tea, Mophead."
"Have a good afternoon as well, Doctor Tesla."
Tesla hung up before Einstein could become any more insufferable.
She lowered the phone with a scowl and stood there for a moment, wondering what exactly she had done to deserve the punishment of being forced to act responsibly.
Then someone sighed nearby.
Tesla turned toward the sound and nearly jumped. For one alarming second, there appeared to be a corpse slumped in an office chair in the corner of the storage room.
On closer inspection, it was just Yssring Leavtruth.
Then again, the distinction was admittedly difficult to make.
The girl had sunk so far into the chair that her oversized lab coat practically swallowed her, arms hanging limply at her sides while she stared blankly at the ceiling.
Tesla blinked.
"... You alright there, kid?"
Yssring's eyes shifted toward her without moving anything else. "I thought I could stop them."
Tesla glanced toward the door. "Huh… How'd that work out?"
"At first, I was just explaining why their ideas were dangerous," Yssring said. "Kiana asked how the separate controllers would communicate, so I brought up synchronization problems. Coralie suggested local feedback loops, so I explained the latency issues with those. Then Kiana asked if the controllers could predict movement instead of waiting for every command, and I explained predictive motor control."
Tesla sighed and rubbed at her forehead. Of course. "So every time you told them why something wouldn't work, they treated it as the next problem to solve."
"... Yes." Yssring's gaze returned to the ceiling. "And they kept coming up with more and more reasonable answers. Then the remaining problems became interesting, and somewhere along the way I stopped pointing out flaws and started suggesting alternatives. I…" Yssring swallowed. "I drew diagrams."
Tesla actually winced. "Oh, kid..."
"I spent twenty minutes explaining how biological motor control doesn't require conscious input for every individual muscle because Kiana asked why a pilot should need to control every joint separately," Yssring continued. "Then Coralie asked whether a neural interface could read motor intent before the muscles actually moved. I told her the signal resolution wouldn't be good enough."
Tesla could already see where this was going.
"Then I started thinking about how to improve the signal resolution." Yssring looked haunted at the thought, sinking a little farther into the seat. "I told them I was just getting water. I haven't gathered the courage to go back. I'm not sure they even noticed that time passed."
Tesla regarded her for a moment, somewhere between sympathy and exasperation. "Want me to call your parents to come get you?"
"No," Yssring responded in a flat, dead tone. "I can't look them in the eyes like this. Leave me here for a while."
"... Alright, then." Tesla turned toward the door before remembering something. "I've got sweets hidden in my lab if you need an emergency sanity refill. Bottom cabinet, behind the old oscilloscope."
That finally got Yssring to look at her properly.
"Thank you," the girl whispered out.
"Don't tell Kiana," Tesla added. "She thinks she found all of them."
With that, Tesla left the girl to recover from the horrifying realization that engineering had happened to her.
.
When Tesla returned to the main laboratory, the first thing she noticed was that nothing appeared to have caught fire in her absence, so that was a slightly promising start.
Kiana and Coralie were still gathered around the same workbench, although several of their papers had migrated into a much larger spread across its surface. Kiana was leaning over the diagrams with a pencil in hand, while Coralie remained perched on her stool with the same open bag of snacks in her lap.
Her expression was as flat as ever, but her tail, meanwhile, was wagging happily behind her.
Tesla narrowed her eyes. "I said not to build anything."
"We didn't," Kiana replied quickly, looking up at her. "We were just drawing."
"Designing," Coralie corrected before eating another snack. "There shouldn't be an issue. I was taught that paper has a relatively low chance of exploding."
… Yeah, this girl was already starting to display the worst of Mophead's personality.
Tesla sighed and walked over to the workbench. "Fine. You can keep working on the idea while I'm here, but neither of you touches any equipment unless I say so first."
Kiana immediately brightened. "So we can build it if you say yes?"
Tesla fixed her with a look. "It means you can tell me what you're trying to build."
That was apparently good enough. Kiana eagerly pulled one of the larger sheets and pushed it toward Tesla, while Coralie's tail started wagging a little faster despite the complete lack of change in her expression.
Tesla took a closer look.
What she'd initially assumed was one humanoid mecha had apparently become several variations of the same concept, ranging from something only slightly larger than a person to one that would have made the base's hangar doors a legitimate design consideration.
She pointed at the largest drawing. "And what exactly is this supposed to do?"
"Everything," Kiana answered proudly.
Tesla raised an eyebrow at the girl. "We would've made a perfect mecha already if that was possible."
"Which is why I gave the idea of exchangeable parts," Coralie explained, pushing another sheet forward. "A general frame with interchangeable equipment would make more sense than designing a completely different machine every time."
Kiana immediately pointed at the rough sketches along one side. "Different hands, tools, light weapons—"
"Rescue equipment too," Coralie inserted.
"—and heavy weapons!" Kiana finished with a grin.
Coralie ate another snack. "They make Honkai Beasts go boom."
Tesla blinked at the blueprints. Were these kids… trying to make a better frame than her Titan?
She had to suppress a laugh.
That exchange, at least, explained how they had gotten this far so quickly. Coralie had enough patience to take Kiana's more enthusiastic ideas, like a perfect mecha who could do everything, and drag them toward something practical, like a frame with exchangeable parts to fulfill purposes per mission.
It was a disturbingly effective combination. Now Tesla was as curious as she was worried about ever letting them see the Moonlight Throne's schematics.
"Alright," Tesla said as she leaned closer to the diagrams. "Say you make the equipment modular. What happens when you replace an arm with something heavier?"
Kiana's pencil stopped moving. Coralie stared down at the drawing as well, her tail slowing behind her.
"The center of mass changes," Coralie answered after a moment. "So the mecha's controller would need to compensate."
"Right." Tesla nodded. "But it can't just guess the exact values instantly."
Kiana tapped the torso with her pencil. "It already knows how heavy the new part is, doesn't it?"
"That tells it the mass," Tesla explained. "It doesn't tell it exactly how the whole machine will move once that weight starts swinging around. If every part is modular, you need to think about how the full body will function with each combination, not to mention with different environments and operational circumstances."
Kiana stared at the paper again.
Coralie's ears twitched slightly. "Then it shouldn't rely entirely on stored values. If the local controllers are already reading movement to keep everything synchronized, they could correct based on what the machine is actually doing. Learning on the fly."
Tesla hummed. That wasn't bad at all.
"You'd still want baseline data," she said, reaching over to tap one of the control blocks. "Otherwise every time you change equipment, the machine has to relearn how to stand. Give it the expected values first and let the feedback correct whatever the model gets wrong."
Kiana crossed her arms, tilting her head at the paper. "So it can also figure out if a part was made slightly different?"
"It could compensate for manufacturing differences, that's right," Tesla replied. "But that's just real-time internal analysis. Don't start imagining the thing growing a brain."
Kiana's expression lit up. "What if it did?"
Tesla regretted her words instantly. "No."
Coralie tilted her head. "Depending on how complicated the control system becomes, that distinction could get vague."
At that, Tesla slowly turned toward the girl. "Don't encourage her."
Coralie's expression hadn't changed, but her tail wagged once. "I was only pointing it out."
Tesla's eyes narrowed slightly. "You knew exactly what you were doing."
Kiana giggled beside them, already scribbling something new onto the paper.
Tesla sighed and returned her attention to the diagrams. There were still problems everywhere. The weight distribution was questionable, their proposed power layout would be miserable to maintain, and Kiana had apparently added a cannon to an arm that Coralie had very clearly labeled 'RESCUE EQUIPMENT.'
She picked up one of the spare pencils. "Also, if you're giving every limb its own power source, this part is wasteful. You're running separate lines through the same protected section when you could split them farther down."
Kiana and Coralie immediately leaned closer as Tesla started drawing over the diagram.
"If you isolate each branch at the joint, you can protect the main line without duplicating half the system. Then if one section gets damaged—"
"The others keep working," Kiana finished excitedly.
"Provided the damage doesn't spread," Coralie added, already reaching for another sheet.
Tesla nodded. "Exactly. And move this controller farther inward. If the outer plating gets crushed, you don't want the first thing behind it to be something important."
Kiana erased part of the drawing while Coralie pulled another page into the middle. "Then the armor around the joints needs to overlap."
"Not too much," Tesla said. "You'll restrict the range of motion. Here, give me that."
She took Kiana's ruler and redrew the joint profile, shortening one section before adding another line through the center. Coralie quietly pushed the snack bag toward her, and Tesla took one without looking away from the paper.
Kiana leaned over her arm. "Could we make the shoulder rotate all the way around?"
"You could, but then routing power through it becomes annoying." Tesla tapped the pencil against the page, considering it. "Unless..."
Coralie's tail picked up again.
Tesla pulled a fresh sheet toward herself. "Actually, forget this version. If the shoulder assembly carries its own distribution ring, you can rotate the whole thing without twisting the main lines. Kiana, draw the arm again. Coralie, give me the controller layout you had before."
Both girls immediately moved.
"And leave more room in the torso this time," Tesla added. "If we're already making the equipment modular, there's no reason not to make the internal systems accessible too—"
.
Yssring Leavtruth, female, 12. Junior assistant at Anti-Entropy's neuroscience lab. Currently wondering whether the emergency sweets had given her courage or simply impaired her judgment.
Either way, she was standing outside the auxiliary laboratory again.
She had spent a respectable amount of time recovering in Tesla's lab, helped considerably by the discovery that the woman's definition of an "emergency sanity refill" involved enough hidden chocolate to survive through an actual emergency.
Eventually, however, Yssring had remembered that her notebook was still inside the auxiliary laboratory, and so here she was, about to put her life on the line for just a few notes.
Before she could talk herself into giving up and running away, she reached out, pressing a button, and the laboratory door slid open.
Then, Yssring stopped.
There were diagrams on the floor. A lot of them, in fact.
Kiana and Coralie had apparently abandoned the workbench entirely at some point, with sheets of paper now spread across the open space in increasingly complicated clusters. The two girls were lying on the floor with a snack bag nearby, writing on the pages as though doodling. Coralie's tail was wagging quite a bit as she reached for the bag.
More pressingly, and to her slowly growing horror, Tesla was sitting on the floor with them.
"No, put the secondary controller here," the red-haired scientist said, tapping one of the diagrams with a pencil. "If you leave it in the shoulder, one good impact takes out the entire arm."
Kiana leaned closer. "Then we put another one in the elbow!"
"You don't need another full controller. Redundancy is good, wasting hardware isn't."
Coralie glanced at another page. "A reduced backup system could preserve basic movement."
Tesla immediately pointed at her. "Exactly. Enough to get the arm somewhere useful if the primary controller dies."
Yssring stared. This situation was, on every reasonable metric, considerably worse than when she'd left it in.
Then Kiana noticed her, and in a moment she was waving at her. "Yssring!"
The other two also turned toward the doorway. Yssring briefly considered running.
Tesla instead waved her over as though nothing about the scene was remotely concerning. "Perfect timing, kid. Kiana told me about that neural command idea you were working on."
Yssring felt something inside her die again.
"I wasn't working on it," she said carefully. "I was explaining why it would be difficult."
"Yeah, well, apparently you had some interesting thoughts about reading motor intent instead of individual movement commands." Tesla shifted several papers aside to clear a space beside them. "Come take a look. If we can get that part working, it'd solve half the control problem."
Coralie nodded while munching on her snack, her tail wagging faster. Kiana was already holding out Yssring's abandoned notebook, opened at a page filled with scribbles that the girl remembered being quite relevant to the conversation at hand.
Yssring looked at the three of them, then at the diagrams, and finally at the empty space Tesla had made for her.
The sensible thing would be to take her notebook, or maybe even write it off as lost forever, and leave before any of this became her problem again. Unfortunately, she'd already noticed three problems with the neural interface layout from where she was standing, and one of them had an irritatingly obvious solution.
With a resigned sigh, she stepped into the laboratory. "Move that input stage farther back. If you're trying to isolate motor intent, you're filtering the signal too late. And with this many modular parts, you need to—"
The laboratory's door slid shut, isolating the ongoing incident within the lab from the rest of the Anti-Entropy base.
Yssring Leavtruth, female, 12. Junior assistant at Anti-Entropy's neuroscience lab. Currently making a terrible mistake.