Typing this down as fast as possible before it exits my brain so you'll have to work with me here
so integer underflow is a thing where a computer number, if it goes low enough, will wrap back around to the highest possible number
this hypothesis/theory/??? thinks that something becoming darker than dark means it wraps around to the maximum possible amount of light
This could explain why determination creates dark fountains if determination = light (either by adding so much light it reaches the maximum, creating a "dark" world, or that it adds so much light it overflows and becomes maximum dark)
This theory implies darkness is not actually darkness. does that make sense? no.
Then why doesn't the roaring make the darkners all turn back into their light world forms?
Going off Ralsei's description they turn into statues, not their light world forms
Also why does dt (determination)=light?
Our soul emits light, if Kris could emit light then they would've during the end of chapter 4
Kris, Susie, and the Knight are the ones with dt and open fountains, not us so dt cannot equal light
where is the proof our soul has dt?
the ability to save and reload is possibly just the result of the device/connection, not determination
that's, like
the whole point of a soul
soemthing something undertale's entire premise and save system, and dark frountains sealing stuff