5 games. All of them delivering something different, while all following a theme of imprisonment, an authority being uncaring or actively cruel to you, and terrifying industrial complexes.
The Other Side has a nice flow, setting up a solid premise and allowing you to slowly learn the gameplay, only to put pressure on you with a timer. The ending, however, is nothing surprising.
Control Room Alpha is the shortest of the bunch. As such, it has the most simple tasks, and beyond the very end nothing too interesting happens. The theme of an uncaring authority shines here, though.
Carbon Steel was my overall favourite. Telling you to do different tasks to extract a sample from an unknown entity three times, with increased challenge including a time pressure for the final time. It offers the most engaging gameplay, the until then strongest atmosphere and presentation, and two endings, although it is not really puzzling to figure that part out.
Concrete Termor delivers the aesthetically most impressive experience. It is the one that abbreviates from machinery completely, instead opting for simple concrete blocks seemingly stretching into infinity. You jump to three different people. Starting out as a citizen who is treated like expendable trash, to someone in a helicopter wanting to shoot citizens, to the third and final guy playing Battleship with the apartments filled with people against someone else.
Tartarus Engine, which was specifically made for this collection, goes back to emphasizing the machine complex. It is, after Control Room Alpha, the most barebones and uninteresting in terms of bare gameplay, but delivers a very strong atmosphere and has some interesting and fucked sci-fi and philosophical elements going on.

Overall, this is really great, especially for free. I absolutely do not regret playing these, and might even return to some of them.