Is it possible you could link/send me your master's thesis? I haven't found a research paper on "2D virtual reality" concepts yet, and your paper may be the first out there (especially since it was written in 2017).
That one's gonna be problematic :D And the reason for that is, I wrote it in my native language which is Polish and it's not translated so I doubt it'll be of any use to you regretfully :( But as for it being the first/among the first ones, that is true - when I was writing it, I could not find anything on 2D VR either, be it in English or Polish :)
I'm also curious how you were implementing parallax (I personally thought it was mostly impossible for consistent 360 degree worlds, but I definitely thought about it less than you, and also other developers I talked to thought it was possible).I did not get to actual implementation cause I did not want to get caught up into the never ending loop of "one more feature" again and honestly just wanted to finally release the game cause the total timeframe started looking a bit embarrasing :) But as for how I imagined it, I though of it in such a way: when you imagine your 2D VR world as kind of being inside a sphere or a cylinder (which are by far two of the best ways of implementing 2D world in VR, both for their own reasons), all you see around you reacts to your head movements like real life would, ie. you turn left -> you see what is currently projected on that region of the sphere/cylinder.
Now, to implement parallax, we could create a secondary container like our first one, say a cylinder inside our "main" cylinder, which would only hold the things on that layer of the parallax, but instead of reacting 1:1 to your head movements, it actually _counters_ the movement - ie. you look to the right, you see what is on the right of your position in your "main" cylinder, but the -1st layer actually spins a bit to the left with each offset you turn right. And the -2nd layer counters the rotation of your head even more to the opposite direction. And so on, and so forth.
Don't know if my descriptions actually make sense cause this explanation begs for using your hands while talking about it to show how these layers intertwine :D But another helpful way to think of it if that's confusing would be to image a flat parallax with its layers and then glue together the shorter ends + instead of having it counter the movement of the camera, having it counter the movement of the _head_ of the player.
Of course we'd also need separate sets of rules for each layer (eg. some of them only reacting to yaw movements or only to pitch, so that they don't all naively follow or counter your vision) but these wouldn't be so hard to implement! This would require some heavy playtesting of course, though, cause this sounds like a proper nauseatorium :D
"virtual reality" (niche) > "2D virtual reality" (niche in niche) > "phone-based 2D virtual reality with a particular bluetooth controller" (niche-ception)Haha, tell me about it!