I followed these games as much as I could on Twitter, because the art direction seemed fantastic.
I will review them one by one, so spoilers, but TL;DR, it's a fantastic collection, and it's free. 
I adored it.

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The Other Side:

Short, and the twist was kind of predictable. I liked the creature design; it's quite interesting, even if it's only seen for a few seconds. 
The fact that you have to read the note first before it appears lessened the impact, since it felt very "gamey", as in something that was triggered by the reading rather than the thing just appearing.
It was a good experience regardless; the tension inside the room was great, and fixing the drill on the fly was very fun.

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Control Room Alpha:

I actually played this one as the last, because I was scared ♥♥♥♥♥♥♥♥ of the spiders once they started crawling out. And once I was prompted to leave the room, I just closed the game and played everything else first.
The twist this time was something I didn't expect at all, and it left me in awe for a few minutes. It was the second strongest experience of the game, and the voice acting was fantastic.

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Carbon Steel:

From a gameplay perspective, this was the most fun experience out of the bunch. I loved the sorting mechanics and the different pieces that were added up with each passing day.
The hallucinations added a great touch, and the sound design was perfect. It's probably my favourite, although I wouldn't call it the best. I personally consider the bad ending to be the canon one because of how much it adds to the dread of the situation.

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Concrete Tremor:

I would consider it the weakest of the bunch. The imagery from the beginning is great, there are some wonderful shots, and the sound design is still very well done. The robotic voices add a lot to the experience. 
However, the gameplay itself is a bit confusing and not really engaging. It didn't really feel like what I was doing mattered, and more like I was just going through the motions before a guaranteed defeat.
It never feels like you have a chance of winning, which makes me disconnect from what's happening, since it makes you an expectator rather than an active participant. It's the complete opposite experience of Control Room Alpha, and that's a shame.

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Tartarus Engine:

The best one. I love the concept and the execution. The tension constantly rising, the rush of time not being on your side, the fantastic imagery, and the horrifying concept. I adore it.
However, I must say two things: first, I feel like the watch was underutilized. Having a physical timer that you have to raise is great, but not having more visual or noise depictions to add pressure (e.g., a seconds counter or a ticking noise) makes it less impactful than what it could be, and the beeping at the end, before entering the room, already kind of sets your expectations for a dire ending, since the deadline wasn't really met.
The second thing is that it was a bit predictable. From the get-go, I knew that the protagonist was going to end up trapped in the eternal torment machine. I adored the sequences directly before and during the actual trapping, but I was more curious of how it would happen, instead of believing there was a chance for escape. I feel like that could've been fixed with a better use of the watch, with you slowly realizing that time isn't running as it should once you apparently achieve your goal, baiting you with a sense of hope before revealing that you indeed are trapped in eternal torment. 
Still, it was the absolute best horror experience due to how haunting it is, and how closely you see the degenerating process of being trapped in God knows how many layers of that machine. 

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Overall, impressive work, and I already want to see more. All of the different concepts are very interesting and amazing to see, especially thanks to the visuals and sound. Please keep doing more games! 

I followed these games as much as I could on Twitter, because the art direction seemed fantastic. I will review them one by one, so spoilers, but TL;DR, it's a fantastic collection, and it's free.  I adored it. [hr][/hr] [b]The Other Side: [/b] Short, and the twist was kind of predictable. I liked the creature design; it's quite interesting, even if it's only seen for a few seconds.  The fact that you have to read the note first before it appears lessened the impact, since it felt very "gamey", as in something that was triggered by the reading rather than the thing just appearing. It was a good experience regardless; the tension inside the room was great, and fixing the drill on the fly was very fun. [hr][/hr] [b]Control Room Alpha: [/b] I actually played this one as the last, because I was scared shitless of the spiders once they started crawling out. And once I was prompted to leave the room, I just closed the game and played everything else first. The twist this time was something I didn't expect at all, and it left me in awe for a few minutes. It was the second strongest experience of the game, and the voice acting was fantastic. [hr][/hr] [b]Carbon Steel: [/b] From a gameplay perspective, this was the most fun experience out of the bunch. I loved the sorting mechanics and the different pieces that were added up with each passing day. The hallucinations added a great touch, and the sound design was perfect. It's probably my favourite, although I wouldn't call it the best. I personally consider the bad ending to be the canon one because of how much it adds to the dread of the situation. [hr][/hr] [b]Concrete Tremor: [/b] I would consider it the weakest of the bunch. The imagery from the beginning is great, there are some wonderful shots, and the sound design is still very well done. The robotic voices add a lot to the experience.  However, the gameplay itself is a bit confusing and not really engaging. It didn't really feel like what I was doing mattered, and more like I was just going through the motions before a guaranteed defeat. It never feels like you have a chance of winning, which makes me disconnect from what's happening, since it makes you an expectator rather than an active participant. It's the complete opposite experience of Control Room Alpha, and that's a shame. [hr][/hr] [b]Tartarus Engine: [/b] The best one. I love the concept and the execution. The tension constantly rising, the rush of time not being on your side, the fantastic imagery, and the horrifying concept. I adore it. However, I must say two things: first, I feel like the watch was underutilized. Having a physical timer that you have to raise is great, but not having more visual or noise depictions to add pressure (e.g., a seconds counter or a ticking noise) makes it less impactful than what it could be, and the beeping at the end, before entering the room, already kind of sets your expectations for a dire ending, since the deadline wasn't really met. The second thing is that it was a bit predictable. From the get-go, I knew that the protagonist was going to end up trapped in the eternal torment machine. I adored the sequences directly before and during the actual trapping, but I was more curious of how it would happen, instead of believing there was a chance for escape. I feel like that could've been fixed with a better use of the watch, with you slowly realizing that time isn't running as it should once you apparently achieve your goal, baiting you with a sense of hope before revealing that you indeed are trapped in eternal torment.  Still, it was the absolute best horror experience due to how haunting it is, and how closely you see the degenerating process of being trapped in God knows how many layers of that machine.  [hr][/hr] Overall, impressive work, and I already want to see more. All of the different concepts are very interesting and amazing to see, especially thanks to the visuals and sound. Please keep doing more games!