For instance once I stepped away from eva, I had one cool idea: all humans are supposed to be psychic right? if this is only visible in a laboratory then I could explain, we've already observed it, as the so called "observer effect" that muddies our interpretation of quantum mechanics, and instead of a specific kind of energy, life energy would then be the telepathic connection all living things share, binding them together into the all, which explains where spirits and that come from...
Likewise, I changed the setting they live in: I kinda went with a world where physics has a more half-life feel, though I borrowed a lot from other sci fi for instance, the 'soul' from Sword Art online... and artificial gravity from firefly, the new setting from cowboy bebop, and some of the future history from ghost in the shell - set 50 years from now, I could decompress my timeline and not bound by having to fit every major world chaning event into the past 30 years, I was able to get my fix for worldbuilding even if the setting is only few cities in one state. Character relationships are the same, but the history is way different... I still have the ruins and stuff, but theres also a lot of world locally too...
