I think everyone who got into games as a kid has this sort of lingering desire to capture a set of very specific feelings again. For some people, it's a first MMO and the social experiences that go with it. For some people, it's love for a specific franchise, usually one that's either dead or being dragged around like a horse that's been killed and resurrected at least twice.
Per-person these sort of things get more specific, of course. For me, it's a sense of exploration and discovery. There's a lot of open world games these days so you'd expect that to be easy, but I don't think most of them really hit the mark; you can go wherever, but that has this weird consequence where I'm never really curious about anything in the distance because I know I can just sort of... Walk there. I'm not stupid, mind you-- I know the main source of these feelings as a kid can be attributed to me being a small child and not understanding that the levels in Spyro were, in fact, small and contained. For a long time, I'd operated on the assumption that these feelings were just one of those things you experience exclusively through nostalgia, since once you understand how videogames work, you know they're not going to be infinite.

Then I bought INFRA during the 2021 Steam Summer sale.

INFRA's one of those games that cannot market itself worth shit because there's really no way to "market" something like it, so instead I'm going to ask anyone reading this a series of questions.

Did you play and enjoy Outer Wilds or Obra Dinn?
Do you have any sort of nostalgic fondness towards games made in the Source engine?
Did you, like me, spend hours digging through TF2 or GMod maps for weird secret shit?
Do you enjoy any sort of 3D puzzle game whatsoever?
Do you have any interest in Urban Exploration or Civil Engineering as a theme?
Do you enjoy mystery/conspiracy stories?
Have you realized that nearly every indie game that comes out of Finland ends up good?

If you answered "yes" to any, and I mean any of the things I just asked, I am begging you to buy INFRA. You will not regret it. Stop reading here. Go buy it. I'm going to keep gushing about how good INFRA is anyways, but I promise you'll enjoy it. If you're not sold, keep on reading and I'm going to pray that I can change your mind.
INFRA did not grab me from the start. The first thing INFRA starts out with is an office, bright and clean and shiny. I'm not one of those people that has a massive hateboner for "Walking Simulators" or "Movie-Games" or whatever, but I have to be in the right mood for one. The first objective you're given is pretty simple: Your name is Mark. You're a Structural Analyst, and today your job is to go investigate a local dam and powerplant to see how it's holding up. Go up to your office, grab your flashlight/phone/camera/helmet/keys, head to the parking garage, and head out. So you go up to floor 8, grab your shit, and...

It was at this point I realized that you could open doors that did not lead to the parking garage or your office.
If you go through the right doors-- mostly propped open by employees of this office building too lazy to scan their keycards-- you can find documents. Take a closer look, and you'll learn a few things: your boss just ordered the destruction of the wrong building a short while ago, for example, and the newspapers are ragging on him for it. Go out the back door instead of the underground entrance, and you'll find an empty geocache.
The game does not make any effort to communicate that you can do any of this. Instead, it's a reward for noticing that some of those doors are propped open, that there's no invisible walls stopping you from digging about, at least for the most part.
The next map starts. The game gives me a camera and a flashlight, and both only have enough battery to be held out for 2-3 minutes at most. You can carry up to 10 spare batteries for each, but in the early chapters you'll be lucky to hold onto more than 2-3 spares if you're careful. The flashlight's use is obvious, so what's the camera for?
Collectibles.

Rotting concrete. Suspicious documents. Disrepair. Everything you're supposed to be documenting as a structual analyst is a collectible, with many, many of them locked behind puzzles upon puzzles upon puzzles. I proceeded to spend what felt like nearly two fucking hours in the first map outside the office. You dig, and dig, and dig, and every time you think you've unearthed everything there is to find in the map you'll find a key or a fuse box, you'll spot a small ledge you can just barely make a jump to, find a strange hidden button... And you lose another 30-40 minutes. Not every door can be opened, not every fence can be hopped, but you dont know that, and I absolutely do not mean that in a negative way.
It just keeps going. Every door begs for you to find a way to open it. Every keypad begs for a code. I finished my first playthrough and checked the wiki, only to find out I'd missed like half of an entire area because I missed a puzzle like ten maps ago that would have supplied an old, decrepit bunker with power and let me through even more doors. I'm doing a second playthrough now with a guide because I want to see everything I missed. I'm begging you to start your first, though I'd advise you do at least one run-through completely blind like I did. This page is hosted on Neocities, which tells me a lot of the people who might end up reading this are the type to fall down virtual rabbit holes and get lost for days. INFRA is a rabbit hole all its own, and minus the half-hour or so I've sunk into a second playthrough, it took me about 22-23 hours to find my way out. I would also like to take this time to mention that none of the images I've used in this writeup are from the levels I'm talking about, just to avoid any spoilers.

I've learned, thanks to browsing the wiki, that INFRA has mods. INFRA also has a still-unsolved ARG. There's so much to this game that even when I dig through well documented guides and wiki pages I still get the sense that there's more for me to find, completely unfound and unknown.
All I can really say is that if any of this has caught your attention, buy it. The Fall sale will come within the next few months, and the game was already hitting 50-60% off when I picked it up in the summer. The devs have already revealed that DLC is planned, hinted to by one of the endings. Not only that, but Loiste Interactive seem to have so much interest in fleshing out the universe of INFRA that they've already put out a spinoff titled "Open Sewer", taking place in the impoverished area of the town most of INFRA takes place in. They're working on a RTS titled "VALTA", taking place in the city's distant future, long after what I can only assume is an apocalypse.
I'm not even sure how to end this post. Like the winding, endless maps in INFRA itself, I feel like I could just keep going and going on and on about this shit for hours if I wasn't worried about spoiling it for anyone who hasn't played yet. I don't plan on doing number-based ratings on this site, so if I haven't made it absolutely clear already: