Game Theory

... basically, the Gamesverse has a history of collapses for a very good reason. Which can roughly be summed up with the word "mages".

—Aleph

Once upon a time, there was a little girl called Nanoha who found a magical ferret...

... except in this universe, Precia Testarossa went slightly less crazy trying to bring back her daughter. And although still obsessed and driven, she realised that the failed clone she'd made is her sole mobile assets, and there are better ways of keeping her under control other than physical abuse. And with that small simple change, the entire story changes.

Game Theory plays up the fact that Lyrical Nanoha is a sci-fi series that just happens to have magical girls in it, rather than a magical girl show, with the aim of exploring this concept more deeply that canon managed.

There are 13 chapters. The story can be found here. Also has its own Alternate Universe oneshot sidestory, Another Way.

Tropes used in Game Theory include:

• Ascended Extra: See Early-Bird Cameo. Also Linith. And then there's the formerly giant cat - she becomes Nanoha's familiar.
• After After The End: All of Dimensional Space is a post-apocalypse place, in that it's still recovering from the end of the Warring States Era and the death of Sankt Kaiser Olivie. Of course, that was recovering from the fall of Ancient Belka. Which was formed from the chaos after the destruction of Alhazred...
• Alternate Universe: An alternate universe of Magical Girl Lyrical Nanoha, where the divergence was that Precia went a bit less crazy. Also has its own alternate universe, Another Way.
• Author Appeal: It seems probable that the author likes cats. Especially kittens.
• Black Box: Alhazredian magic is this by the standards of modern mages. Note that this doesn't mean it's better; to use a Powers as Programs analogy, Alhazredian magic was is the equivalent of computer programs done in the days of punch cards and vacuum tubes. They pretty much took spell bits that worked and put them together without regard to anyone being able to understand it (and as the Alhazredian priest-kings guarded their knowledge jealously, they wouldn't want that to happen anyway).
• Butterfly of Doom: The fic runs on this.
• Child Prodigy: Nanoha, almost freakishly so, and lampshaded in-universe. She grasps magic freakishly quickly, competing at the same level as Fate when she has years of experience compared to Nanoha's months. And up against the TSAB back-up squad, we see that Fate is like that to them. So Nanoha is the Child Prodigy of Child Prodigies, then.
• Child Soldiers: The TSAB, viewed objectively. Nanoha refused to believe that Chrono was a real policeman partly because he was too young. Also, Fate.
• Culture Clash: The standards of dimensional space, compared to Earth.
• Dark Is Evil: Played with. Nanoha is innately prejudiced against Chrono for the fact that he's too young to be a "real policeman", and his appearance.
  • Nanoha: "The TSAB are bad. They call their policemen 'Enforcers' and they wear black and have spikes on their shoulders."
• Darker and Edgier: It plays a lot of the elements of the series more seriously. And dangerously.
• Early-Bird Cameo: Tiida and Teana Lanster, Zest Grangeitz, Quint Nakajima, and Megane Alpine. This is while Tiida, Zest and Quint were still alive, and Megane is pregnant with Lutecia...barring a change from the Butterfly of Doom. Gil Graham is mentioned in passing, and while the story doesn't say the girl in the wheelchair is Hayate, it almost doesn't need to.
• Everything's Better with Dinosaurs: Nanoha and Fate encounter a dinosaur-descended creature which resembles a hippo a little bit on a divergent Type-1 world which apparently had a lot of dinosaur-like things survive. They run away, and manage to stop Arf attacking it. There's also a little almost ape-like bird-dinosaur with teeth and whisker-like feathers on the same world.
• Face Heel Turn: Nanoha. To be fair, she doesn't realize Precia is the villain.
• Fantasy Counterpart Culture: Based on linguistics.
• For Want of a Nail: Precia stays a little more sane. The changes all flow from that small change.
• Ill Girl: A little cancer patient in a hospital called Chikaze. Who turns out to be Badass Adorable when she pushes a zombie down the stairs. Bound to become more important to the story, given that she saved a certain girl in a wheelchair...
• Insignificant Little Blue Planet: Unadministered World 97 (called by natives "Earth") is a backwater Type-1a world which is only really notable for its low average magic level, and the fact that it's a Type-1a.
• Little Miss Badass: Fate, and especially Nanoha, who has started to disturb Yuuno with how fast she's picking things up.
• Lost Technology: The Lost Logia.
• Magic Versus Science: Nanoha thinks that magic is magic. This worries Yuuno rather a lot, because it means she does things because that's how she thinks magic should work, rather than following the clearly defined scientific principles, and has enough raw power to be sloppy when she does it.
• Manipulative Bitch: Precia in spades.
• Missed the Call: Given that Another Way is an Alternate Universe of Game Theory, this is Momoko, Nanoha's mother's position in life. Has lots of raw magical power, but misses any chance to actually use it because she was born on a world where there weren't any mages.
• More Than Mind Control: Precia's means of control are classical methods; measured praise for doing what she wants and condemnation for failing her.
• My God, What Have I Done?: Chrono gets a low-level version of this when he realizes that Nanoha is actually from Earth...and he attacked her in her house.
• Nice Job Breaking It, Hero: Chrono had no idea he was attacking Nanoha in her house...which is the catalyst for her joining Precia.
• Non-Lethal Warfare: Played with. It holds true in greater Dimensional Space due to deliberate design intentions in magic, but it's clear that it's really less-lethal warfare, and as we see in the first chapter, just because you're not killed doesn't mean you're not injured.
• Nothing Is Scarier: A description of an attack from one of the Jewel Seeds:

A segment of the forest was gone.
Not destroyed, reduced to kindling by the terrible force and momentum behind the orbs. Not broken or smashed, frozen or cut. Just... gone.

• Off the Rails: How off the rails? Nanoha decides to help Precia. The nature of the Early Bird Cameos may also derail the sequel seasons.
• Original Character: Chikaze and Tiida's squad.
• Poor Communication Kills: Remember how Yuuno didn't tell Nanoha he was really a human? Well it's not Played for Laughs in this story. Also happens to Chrono.
• Took a Level in Badass: The Jewel Seeds. One erases the landscape, while another creates zombies.
• Was It All a Lie?: Nanoha is made to feel this way towards Yuuno.
• World Building: Aleph has done a great amount of this, expanding and occasionally modifying the Nanoha universe. Many readers consider this fanon to be superior to the official canon. Indexed here and here.
• You Can't Go Home Again: Nanoha, after joining Precia.
• You Gotta Have Blue Hair: Justified. The reason people have funny hair colours is that the Alhazredians encoded tribal markings and lineages into their genetics, and so they're "natural" results of genetic tampering. The reason they exist on Earth (like with Suzaka) is evidence of genetic contamination from Dimensional Space at some point in the past.
• Zombie Apocalypse: Caused on a small scale by a Jewel Seed.