Seeing as I'm a big fan of cinematic platformers, it's taken me a while to finally play this game, and it turned out to be very surprising experience to say the least.
There are certainly more than a few parallels to (or influences from) Another World for sure (one of the first dogs chasing you towards a ravine felt very much like the beast chase sequence in Another World) as well as Heart of Darkness (or the genre in general, a boy dying in many gruesome ways). It's a masterfully crafted game that takes the formula and perfects it for the modern age, especially in the movement and animation department. As was often the case with Another World, INSIDE has a lot of unique situations and cases where an action (and its respective animations) occurs only once in the game, so mechanically speaking, the game was designed in a way to always give emphasis to the visual/physical narrative, no matter how short or insignificant the situation or "story bit" is, which is always pretty crazy from a game design standpoint. Sure, there are some basic gameplay mechanics that are always repeating, the mind control helmets, simple walking and jumping, but there are so many variations even in these simple mechanics that it must've taken them a while to make and fine tune so it all feels seamless. Also a very consistent game visually and technically, with great IQ, smooth performance, a treat. The only real problem I have with it is that the game hasn't explored its gameplay mechanics to their full potential, and some of the sections felt a bit too stretched out, while they might've instead used that time to push the gameplay ideas of control stacking a bit further. But it's a tough balance to make, because some of it could've easily hurt the flow of the game to the other extreme.
I loved the shift in tone near the end, the body horror fever dream rush was extremely effective at creating a sense of dread, and I think it manages to pull off what they set it out to do. I was wide eyed the entire time and had strange spikes of disgust, awe and occasionally getting deeper sucked into the game that I forgot I was controlling this disturbing mass of flesh and then shifting back to the awe and disgust. Can't remember the last time a game manipulated my emotions in such a way, but it was really well done.
As for the meaning of it all, I haven't really read a lot of theories, skimmed this topic a bit, and should probably go through the game at least once more, to see things in a new light. I would like to say that I feel it strangely has a lot in common with The Witness, and I don't just mean in the "pretentious" confusing sort of way. The narrative is clearly heavy with metaphor, but it also is closely tied to depicting the "creative process" in general, or the process of game design, if you like to tie it more closely to the medium the product is made for.
I've posted some ideas about The Witness when I beat it (spoilers of course), and I think there are some interesting similarities there.
INSIDE might have a more superficial narrative on the surface, something about an oppressive regime with the total disregard for humanity, bound for total control etc. but the clash between the very grounded looking forests, farms and cities and the later surreal environments, the thumping, gravity defying water and the fleshy blob and the scientists' reactions to it intentionally hurl the narrative into dream (nightmare) logic territory on one hand, and I think also show the underlying structure of the game's idea. I mean, it's left open ended intentionally, just like The Witness in that respect, so all we can do is give interpretations and maybe get closer to the inner workings of the creators' minds, to understand them better. Apologies for the wall of text.
Game developers create a game and give it into the hands of the player, the participant. Some games are made for simple fun, others to encourage competition, or tell a story etc. The point of this particular game is to let the player experience the process of creating the game itself, or rather the creative process that led to its creation, through the lens of gameplay mechanics and metaphors. However, it might also go as far as to imply that through that creative process, it's really the idea that controls the creator, so the creative person really has no choice but to follow where their inspiration is taking them.
So in this case, the boy is the raw, wild, uncontrolled idea, the spark of inspiration, drawn towards its natural goal. The reason it's young is probably to better depict its fresh, novel aspect of itself (and to throw off the player). It's hunted down by reason, the need to make sense of it, control it, put it in a box and give it shape, perhaps even kill it because the mechanisms of rational thought see it as useless and obsolete (the guards, dogs, machines).
It manages to evade these attacks and survives, and arrives at a fertile ground (the farm) where it starts to experiment and slowly reveal its basic nature, its concept (control). The original idea sees its brethren and bends them to its will. Lesser bits of concepts and ideas are drawn to its magnetic nature (chicks, fish), and influences from other sources and experiences start to endanger the "originality" of the initial idea (the parasite worms), but the idea survives, endures and slowly changes.
The idea is slowly changing, it's evolving through the "experiences" of the thought process, and it starts to explore other venues, broadens its horizons (the city). Hundreds of ideas and concepts are hoarded and funneled through the machine like hordes of zombies walking through the streets while the agents of reason guide them to their predetermined, expected function. So there lies the first great danger - should the idea run wild and free, or should it be molded into what the industrial machine is expecting of it. The idea runs and hides, but at one point is even caught into the same factory assembly line (walking in line section, the creative person struggling between making pure art or a commercial product, or the devs contemplating on shaping the game into more traditional, industry standard molds or into a thing of its own), but is discovered as the deviant that it is and is chased away (the idea never wanted to be in the mold anyway).
Still, the pursuit is deadly and the idea is forced to dive into the depths of the creative process, of imagination, to find its true path (the submarine area). This is the collective ocean of creative thought, deep, dangerous, but ultimately necessary to dive into, if you wish to create something truly unique and of essence. Entire products and almost-finished ideas lie dead and flooded (facilities and buildings). On the way, you encounter the half-drowned, struggling corpses of past and future ideas (the mer-boys/girls), young but almost stillborn, drowned and buried before they even had a chance, or they maybe never deserved one, so they are bitter about and jealous of what the boy represents (they want to drown you as well).
The idea yet survives and emerges from the depths, perhaps more refined and formed (alas, such is its nature, wants to be wild and free but must be defined, and confined to become something, to exist), or perhaps as wild as it ever was. It reaches the shores of an abandoned mine (factory?) where it experiments with its basic concept by controlling and manipulating a much larger group of lesser concepts (the 20 zombies puzzle, conveniently placed besides a U (You) sign, as in - "this is what you are") and seeing where that goes. It firmly establishes its basic concept, and what follows after can already be heard beyond the gates.
As the idea is firmly established, what naturally follows is the grind (the bridge), the unavoidable practical work that comes with any creative process - you need to write, paint, code, compose or place the metal on the anvil and hit it with a hammer, over and over again until it bends to the will of the creator. The process is as dangerous as diving into the depths of creativity, maybe even more so, because now you're committing to it with every keystroke, every hammer strike, so every mistake is deadly and every move must be calculated and timed well in order to succeed.
The struggle ahead is made out of many of the basic concepts, everything contemplated is now being encountered and tried, and as there seems to be a goal in sight, the idea hits a dead end, and is dead in the water. But from that same, seemingly insurmountable obstacle, the idea draws new inspiration from past, discarded concepts and emerges stronger and more alive than ever (death and rebirth scene).
With its newly found clarity and strength, the idea enters the phase of experimentation and finalization, having the creative process down to a science (research facility). The other fresh ideas are neatly stored and kept in check, everything has its place and purpose to it, and in turn, that order gives greater freedom to experimentation and impossible designs (gravity, water), the creators feeling like they have a firm grasp on the universe itself, feeling that anything is possible.
But what do you do with all of this inspiration, knowledge and work? There's something forming in there, but it's without purpose. As I mentioned at the beginning, there's the creator and its creation, and it's never really clear who's controlling who. All of the controllers, the creators, rush to their creation, with a heavy smell of expectation in the air. The idea pushes through and sees its greater self for the first time, sees the formed, packaged idea in a box, barely contained in its complexity and absurdness (the blob). But this completed work sits there, slowly forming itself (it has "absorbed" other "boys" before, it's a "product made out of ideas"), sitting and waiting. It seems its creators have been at it for a long time now, waiting the moment to release it into the world. They've planned its release, made blueprints, models, thought about how it will all work out in the end, and it looks like it's finally time.
It's just that it never works out the way you plan it. The idea has a will of its own, and even with all the preparations and work that gone into everything, it still wiggles out of their grasp. The final piece of the puzzle is added, and this weird, "finished" thing wants to run loose. Shit starts to break, the whole operation is coming apart at the seams. They try to contain it, to guide its release in a less painful way, but you really can't, it's like giving birth to your baby, because it's a raw creative force that wants to impact everything and everyone. The casualties ramp up, things happen, people are hurt, yet they still try to restrain it and put it in a bottle, maybe delay its release, maybe it's not ready, maybe it never will be, or just selfishly keeping it for themselves. But again, they can't, so it breaks loose, starts tumbling down uncontrollably and is finally released into the wild.
There are probably some obvious holes or lapses in logic in this theory, and I don't think this theory is better than any other one, but it seems there's an aspect of the story that is more closely tied to this idea of the creative process. The world in the game might also represent the world out there in general, social influences trying to force you into a mold, killing your creativity, and the research center more specifically being the developers themselves, living sort of isolated within this world, but toying with forces they barely understand until the uncontrollable force of creativity forces them to finally commit, the whole thing just gets a bit out of hand and is "finished" as a product for release.
In any case, this turned out to be a wonderful game, probably not perfect, but worthy of praise IMO, and I hope other devs will take notice and take inspiration from this.