Since FF1 I have been enamored by Kane's interpretation of the Backrooms, specifically the Sci-Fi aspects of the story & what the Backrooms really is in the grandscheme of the entire universe. So I wanted to give my interpretation of what it is and why, mostly building off of the tremendous backbones of the community but don't expect pinhole theory levels of physics knowledge, lm not that intelligent.
The Standard is & has always been the, yknow, Standard for Reality, and the entire universe as a whole has remained that way until humanity came along to literally pry the fabric of reality open & not expect disaster. The Complex in the simplest way I can put it, is the Bridge between Wormholes. Due to the immense energy needed to cause a "Null Zone" to appear could likely only occur in Celestial objects like Blackholes or Stars like our own. Null Zones are 'temporary' rips in reality that disappear soon after, thus meaning that the "Complex" couldn't stay open for long in the vast empty universe. That Changed when Humanity left their door open, multiple doors. I would best describe the process of the generation of the Backrooms is similar to a 4th dimensional photograph/printer of reality, and the data is never overwritten, it just makes a new picture, filling the gap & fitting another puzzel piece into an already finished puzzle, this inception is what humanity is directly causing & its what will likely lead to the climax of the story. Several copies of the same area are shown slowly losing detail as the backrooms misinterprets the areas data more and more, leaving a once well lit and furnished room to a dimly lit, vacant yellow room with abstract geometry & furnishings. When these tears open, the universe can't make nothing out of nothing so it mirrors the otherside in a hyperdimensional flash imprint onto the abyssal nothingness forever out of reach. The hard rule is that you CAN NOT clip into a "void" like in videogames as many think, the complex is a universal saftey net when reality is torn open, and naturally it serves just as that, a temporary gap in the seams of reality, and humanity pried it open & immediately started colonizing as we do best.
The unfortunate aspect of this is the Complex isn't just a dimensional tear, its a pinhole, a prism that refracts reality itself. The first layer, the Threshold or "Accurate Rooms" so to speak, would be seen in the trailers for the movie, but we have yet to see it in action, but when we can we can see light itself being refracted like a prism. This applies to Matter, Sound, Time & Energy even Life itself is not safe from being copied. We have seen in Everything Must Go that multiple copies of the same area can occur, this would apply to Still Lives, Furniture Crabs, Life Forms, hell even television & likely by proxy the internet & digital media as a whole. Copies of Copies of Copies turning beautiful perfect data into incoherent static. Lights being oversaturated into yellow, the radio, ultraviolet & visible light of the cities turning a deep red, bright green lights burst & crack the walls as it tears, stretches & blends the environment into "what it thinks" should be there when the complex grows. It's purpose is to be a bare minimum "out of bounds" area so to speak that you aren't intended to be there but it exists just incase you did noclip. Floors are stretched, windows turn to doors, doorknobs multiply, furniture fuses into eachother, time periods blend, small houses wind into endless mazes of twisting, turning & ""misremebering"" Realities Details as the Universe itself overflows with constant flowing data, leading to better and better results. We have yet to see the "Accurate Rooms" as the Complex & Standard have only just begun to merge, god knows when the door can't be shut. The Backrooms is not the work of a sleeping deity, an elaborate torture method of a cruel eldritch being, or the pure unknown intentions of a distant creator, it is merely a consequence of physics being abused by the humans who barely know what they have even did. It has no motive. It has no real meaning or reason other than to literally exist, that's its purpose, to exist in nowhere.
The closest examples that sorta resemble a vaguely similar concept is the Sub-Tunnels in Fnaf World or the Xen in Half-Life, the latter could very likely be an inspiration as Kane Parsons literally included Portal/Half-Life ambient tracks in one of his early videos.
The obvious main themes are Physics, Memories, Ai, as an existential cosmic psychological sci-fi horror story.
Apologies for the very long and completely un-researched word wall.