Subterrain

Executive Summary: This is, easily, one of the most underrated indie titles, EVER, on steam.
Detailed review:
First, if there is anything negative to say about this game it's two things:
1) The beginning of the game lulls you into a false sense of security and control
2) The final boss isn't really correctly telegraphed so you can't prepare for it and have to waste some time going back and preparing.
So what is this game? Generally, I divide survival games into three main categories:
1) Puzzle Survival
These are like Resident Evil where the emphasis is placed on individual survival via solving puzzles and fighting enemies. It rarely has elements of gathering, aside from ammo, and individual self-care (like eating).
2) Resource Survival
These are like 7 days to die, Minecraft, Don't Starve where the emphasis is placed on individual survival via self-care (eating, drinking, etc...) and scavenging. Scavenging nets you resources and/or blueprints that can be used to upgrade your defenses and base. These rarely emphasize puzzle solving to the degree #1 does, preferring to concentrate on the individual vs. the elements type of play
3) Logistics Survival
These are like Factorio, Mindustry, Satisfactory where the emphasis is placed less on individual survival vis-a-vie individual actions and more on logistics. Resource gathering is present, but is mainly used to drive the development of a facility. Puzzles are there, but they're puzzles of efficiency and optimization and not specific game implemented ones.
Subterrain is a weird mix of 1 and 2 with the main emphasis on 2. There ARE puzzles, but these are more like "read this log entry and look at what is highlighted to determine where to go to get the new tech up". 
Thus, there is a LOT of gathering and, in this vein, it is more similar to the 7 days to die type than anything else. However...it is ruthlessly unforgiving. In most survival games - with the possible exception of #1 - there is a point you reach where you recognize that you are, for all intents and purposes, going to win. In Factorio, it's having a factory that is basically unbreachable and producing plenty of excess, and, since you have done enough, you can now explore and not have to deal with the pressure of immediate survival.
I NEVER felt like that in this game, and that actually made it an ENJOYABLE experience.
But...
If you aren't prepared, especially at the later dates in the game, it will turn into a grind that will have any Gen Z fuck playing it crying to their parents and alleging the game is not respecting their lived experience at having always received accolades for merely booting up a game.
And this is what I mean by it being a weird mix of 1 and 2. In 7 days to die, there is really only pressure at the 7th day or at night, and rarely, if ever, do the zombies tech up beyond your ability to defend (or run) effectively, even at the base weapon tier. Here, that can happen, and it can lead to a few hours of frantic and painful gameplay. This can be avoided if you remain consistent in exploration and production, but it is a larger threat than normal; and, again, makes for fun gameplay in avoiding it.
TL:DR - the game is criminally underrated but it CAN be difficult if not prepared. If you want an easy walk in the park, look for something else. Otherwise, pick it up, you'll get your money's worth.
And, as always, comments open because I'm not a bitch

There are a lot of underrated indie gems out there that truly deserve more recognition and this is one such game. Subterrain is a sci fi horror top down shooter with survival elements. In my own interpretation, the game is set in a time where technological advancement has ushered a new era of interplanetary colonization namely mars, mining it for its rare minerals and scientists expanding new horizons of research and knowledge than ever before. Nanotechnology revolutionized manufacturing on an unprecedented scale and functions as one of the essential gameplay mechanics later on.
You start off in a mars prison cell as a Dr Albert West who was wrongfully convicted for the death of a colleague. Upon escape you realize the entire mars colony has been on lockdown. Dead bodies of colonists litter the facility and logs provide you with details to events prior to the xeno outbreak. The game has a dead space feel to it. You make your way to central control via tram and it serves as a bastion of safety, recuperation as well as daily operations for research and production.
By accessing the central control terminal, you can distribute power throughout different districts of the colony and travel there via tram. The reactor cores also located in central, sustained considerable damage and you'll learn how to repair and maintain them from the tutorial, install security turrets and eventually defend your base from mutant invasions. The modules' durability will decrease over time and affects the amount of power generated. The less power it generates overall, the less amount of sectors you can allocate power to, which factors in planning and decision making. Exceeding the maximum limit of power may result in a nuclear meltdown. Though the player can craft advanced core modules later on enough to power all sectors. A sector without power means that it doesn't have oxygen and thermal regulation.
You'll also learn the differences between global infection, rate of infection and regional spread. Infestations in some sectors can be so severe that you'll struggle to clear them without the use of more powerful weapons. Higher levels of research software enables crafting advanced iterations of standard weapons, armor and equipment, oxygen canisters with higher capacity and purification filters that rid an entire sector of infection, just to name a few. As Dr West, you play as a janitor, soldier, scientist and engineer all in one. Simply one of the most satisfying and addicting indie games I've ever played.

To the developers:
You've made a very good game, but it takes far, far too long to complete. It took over 50 hours of the 62 hour playtime to finish on normal, far too long given the limited variation in gameplay. If you ever make an enhanced sequel, please consider adding options for different gameplay lengths (i.e. a regular version which takes half as much time to play, along with an extended version).
More variation would be nice across the board. More enemy types, mission types, NPCs, weapons and environment types would all improve a sequel.
To potential buyers:
You'll probably like it and have fun, but you may not finish it. The gameplay is solid, focusing on a loop of explore / loot / fight -> return to base / recycle loot / get upgrades. There is some depth in the upgrade system, which involves sourcing chips to manufacture and research better versions of weapons / equipment / armour.
The survival mechanics include injuries, food, water, oxygen, heat and contamination. There's reactor you have to maintain and defend occasionally, and an infection mechanic. As infection in the different districts increases, more and more difficult enemies appear, but you can slow it down by killing enemies and placing upgraded oxygen and thermal filters. The boss fights (especially the final one) are VERY difficult.
Presentation is decent for an indie game. The story is minimal, but there are a number of quite funny logs to be found - these comic parts stand out much more than the main story, which has been done a thousand times already.

While I would recommend it to people into this style of game, I do have to say that the game is rough around the edges. It shouldn't come as a surprise being an indie-game title. I'm not saying the developers of Pixellore are bad, far from it after playing through their first published work on Steam, but don't come in expecting it to be 'perfectly polished'. Their tech support is very responsive and friendly if and when a bug come up! (even 4 years after release)
That said, let's get into it!
The gameplay loop is pretty solid. Even when behind on the crafting and tech advancements, it doesn't unduly cripple progress; which can easily happen in games of its type. It reminds of the Decision flashgame series (yes, back in the day), by FlyAnvil. What this game does differently is that it plays as tense sci-fi dungeon-crawl. The darkness and lighting effects are done well as your character relies on a mere flashlight, and sometimes muzzle and grenade flashes, to see what's going on in his field of view. Even after you get the room lights back on, you still can't take it easy, since you have a slightly less than 90 degree visual arc to work with. So keep that head on a swivel! The combat system is different than Decision, being more geared for grittier close encounters and tactical maneuvering.
Added on top of that is the survival aspect where, you have to not only worry about food and water, but most importantly infection, a few key debilitating status effects, and healing damage you will inevitability get. At the start you cannot instantly (or near instantly) heal or recover from bad status effects, which plays into the survival feel pretty well. Some survival mechanic quirks, like in-game needing restroom breaks is interesting, but thankfully doesn't seem overbearing. That aside, the typical worries of healing from damage, recovering from the occasional status effects, and managing your held resources as you loot for more seems to be executed well.
While the crafting and research mechanics is fully formed and every functional, a good part of it is for plot, ubiquitous gear progression, and much needed item restocking; for better or worse. There isn't much in the line of advanced features, crafting combos, or hidden secrets to research for building something especially exciting. It could be argued that it keeps things from being bogged down; making the process straight forward so you can get back to exploring and clearing floors. That said, crafting and researching is still enjoyable, and getting end-game gear is satisfying; but unfortunately some gear just doesn't meet expectations.
As for the rough edges, there are a few that could turn some people off if not prepared. A main one is how easy it is for a player to miss important info on their first play though, either towards progressing or towards using some features properly. While it is clear that the developers have put in a lot of work to make sure relevant info stands out, and does work well for almost all cases, some details can still slip by. Another could be the inventory system and inventory space. I believe much of that is intentional. You aren't Doom Guy, or Freeman, carrying hundreds of pounds of gear like it was nothing. That said, the general feel of the interface can feel a bit off, and the inventory management could use a couple more quality of life features (on top of the ones that are thankfully in there already). The feel of the game could be off as well, and if that's the case, do check the game settings and features. UI size, sound, camera drift, etc might not be to your liking on default settings (don't be afraid to change them!), Lastly, the combat mechanics could take some getting used to. You can leap away to dodge, plus you have an energy shield to block some damage; and while very useful, it took me awhile to get the hang of dodging on mouse and keyboard (but for others it might not). Also, being swarmed by attacks is liable to stun-locking you (sometimes to death), and there are no invulnerable frames (i-frames). Just saying! Doing stupid 'heroic' stuff is likely to get you killed. (which is likely the point)
That said, the game is pretty enjoyable, once you get the feel for it. It does turn into a repetitive grind at times (especially once you've seen all the enemy type), but that's to be expected. To my surprise when at the very end, even with the maxed out gear I got, I still had a run for my money. There is a story there, with interesting background details (and item descriptions), but you can take it or leave it however you wish; and just enough the survival dungeon-crawl.

I would recommend it ... up until the final bosses.
The entire game 'trains' you to be cautious opening doors ... that there is a good chance you'll get overrun if you don't backpedal quickly ... but the spaces you fight in are generally narrow (or you can easily retreat so as to funnel your enemies). The crafting and other survival elements are quite well done ... but then there's the final bosses, which made me rage quit in the end ... partially because it's broken/bugged partially because the game has, at no point, 'trained' you for that moment.
First off, the bug. I stop shooting. Literally pressing the LMB does nothing. I can be shooting full auto with an SMG and then ... whoops, you're done. No more shooting for you. Try to change weapons? No animation to change weapons (although you do get the audio). Try to use other abilities? Nope. Just Exit and Reload. Again. And again. And again. And again. I just gave up after an hour and a half where maybe 2/3rds of them was because of this bug.
But then there's the bosses themselves. The first one is pretty benign once you keep your distance, he does a lot of charging WAY more than ANY other mob in the game (they're all slow, ponderous zombies, this guy is like greased lightning). Then there's the final boss ... not only does she have multiple different kinds of ranged attacks, is just as fast as the other boss, summons minions, and she has a shield that regenerates and podiums around the map that heal her. Not that it's obvious that that's what they do.
No other mob in the game heals like that. No other mob in the game has a scattershot like that. Virtually no other environment is as wide open as that. I get that you don't want the end boss to just be a souped up version of another mob, but you can have hints along the way ... podiums in other parts of the game that heal nearby zombies ... other zombies that fire off blasts similar to hers (explosive or bullet hell) ... so that we get the idea, the theme, that she's an amalgam of all these others.
I went from a walk in the park to a sudden brick wall when I hit these bosses. These were not properly vetted or tested IMO nor were they properly included in the stream of the narrative, of one ability building on another, of one environment being similar to another.

Just enough of what should be just enough to avoid annoyance (crafting, survival aspects), plenty of what should be always plenty (atmosphere, tension, feeling of progression). Simply put, it's brutally absorbing game.

This game is survival-horror at its finest. There's a minor learning curve to surviving the first few days efficiently, but once the basics are in-place, it gets pretty exciting exploring the world slowly.