hey guys lets make an RPG!

I have had a idea similar to this brewing in my head for a few years now and I've been meaning to share it here ever since I saw this. I could go on for pages and pages about this but I'll try to keep it short. 

So the idea I had for a world like this is like a post apocalyptic world where a huge nuclear war took out all of the worlds governments, but the world is set several hundred years after the apocalypse (like 300-500 or so range) and it's to the point where its not really a post apocalyptic setting anymore, the world has returned to a new normal and its now in a medieval like state. So the world is now kind of like the middle ages/ renaissance times but at the same time humanity still has knowledge of how to make things like automatic guns and they have modern science knowledge. But at the same time they don't have access to oil or large amounts of fossil fuels and no way to refine them like we do today so there would be no engines or tractors to help with farming or cars or anything like that. They also wouldn't produce electricity on a big scale like we do. (Another aspect I imagined is there are a bunch of different countries/governments/states all competing for power, kind of like the warring states period in ancient China or the Sengoku period in Japan.)
So pretty much the world now operates like the middle ages, not because its trying to copy the middle ages, but because this is just the point where humanity is at, if that makes sense. 

BUT there is a twist, somewhere, there is something manufacturing large amounts of digital technology, like screens and wires and circuit boards and computers and shit like that, (and I also imagine this "center" where all this is coming from being in like the middle of an old world city, or somewhere that is otherwise really built up and developed, before the bombs dropped that is. Also realistically after like 400 or so years most major cities are probably not going to still be standing, especially the ones that were affected by the bombs but it makes for a cooler setting if we ignore that lol.) and so now there's this one spot in the middle of some old city or something somewhere that inexplicably has all this like cyberpunk shit going on, and it becomes a hotspot of interest for people and different governments/states. I also think it would be cool if the world ended like sometime in the 2000's or something so all the technology and computers that are coming back is all stuff from like the 90's/00's, like classic computer stuff. And maybe the war happened not because of an alternate history with alternate global tensions, but just because of a freak and suspiciously surgical accident that launched a bunch of warheads and caused everything to very quickly devolve. (perhaps the thing at the center of this bastion of digital technology is behind this? This would also make it so we don't have to make up an alternate history that caused a nuclear war to happen, it can just happen.)  So the rest of the world is like this natural middle ages like landscape where people ride on horseback and wear metal armor but also people have guns, and all of the structures would be made out of like wood and stone. And then in the heart of this old city made out of modern concrete and rebar you have a bunch of digital technology popping up, and you have like clubs with techno popping up, and its full of wires and screens and circuit boards and CD's and all this stuff, it would be kind of a like a Serial Experiments Lain -esque labyrinth of 90's/00's digital technology. I also imagined the thing at the center to be like the anime girl angel from Killer7. Like a somewhat generic, doll like, perfect looking anime girl angel.
I'm not entirely sure what the plot would be but the idea I have is maybe the protagonist is connected somehow to the angel at the center and is called forth by it for some reason. Maybe the protag somehow existed/lived before the bombs dropped and has deeply buried memories from that time and that makes them special and something of interest for the angel? Maybe a government/clan/country has a monopoly over that area and its an allegory for big corporations controlling the internet or something. 

Something I thought of that the main character might wear and something that exemplifies this "new normal" middle ages -esque world is a metal helmet that also functions as a gas mask and it's shaped kind of like a great helm.

TL;DR: Its a post nuclear-apocalypse world that is several hundred years (300-500) after the bombs dropped and the world has returned to a new normal, not really post apocalyptic anymore. This "new normal" is a world that operates like the middle ages, but people still have modern knowledge of things, so people still know how to make automatic guns and electrical generators and things like that. But no cars, no engines, no instant messaging, no electrical grid, no industrial revolution type stuff going on, things more or less operate like middle ages times. But there is a twist, in the heart of some old world city or something, a bunch of electronics and digital technology from like the 90's/00's era is inexplicably popping up, and its amassed a lot of attention from individuals visiting it and also governments/states/countries are also interested in it. So you have a middle ages like world and in the middle of it is this weird cyberpunk "city" has formed that doesn't belong to any one particular person or country that has re-introduced electronic/digital technology to that little region. 

Ok I've spent a lot of time writing and my brain is kind of fried and that ended up being kind of long lol but yeah I have a looot of ideas about this world and this setting. There are even more things I could say about this but I hope I got it across well enough. 
This is also just an idea that I had I wanted to share to help brainstorm, it doesn't have to be and end all be all type of thing. If anyone has thoughts/ideas id love to hear em!