Going into details. There are spoilers here.

• Meeting real humans was very rare. The only “real” encounter was in the beginning, back in our time, where a guy in a blue shirt instructed me to take a seat.
• Just as in Amnesia, I had to click and hold things like doors and drawers then move the mouse to open them. It quickly felt so natural that I was wondering why this wasn’t more common in video games.
• Sure were a lot of chairs in my way when approaching desks that I had to move away. I get why they had to be there, though. I guess it couldn’t have been any different.
• Sometimes windows had to smashed through, and only a fire extinguisher could be used for this.
• Lots of audio logs. Sometimes by “sensing” past dialog when clicking corpses or on wall recorders. At other times there were audio logs on the computer, or an old fashioned tape recorder in a drawer.
• In the beginning of the game I sometimes had problems understanding when I could jump and crouch versus clicking the edge of something that the protagonist would then climb.
• Most of the ocean floor sequences were pretty much walking simulator territory. Sometimes a cute spheroid-type robot would tag along and open a door by welding it. It reminded me of ABZÛ.
• Tables or desks in the more “important” rooms typically had a few photos or documents I could zoom up and rotate with the mouse. Almost all of them were only to satisfy the player’s curiosity.
• Being exposed to the water of the ocean was a surreal experience at first. I was wondering why I suddenly had some sort of diving suit on. It later turned out I was kind of a cyborg, but still.
• Health rechargers sometimes occurred as organic sphincters that I had to put a hand into. I did that after e.g. a drop, but I’m not sure if it was ever necessary because of the safe difficulty setting.
• Did those surveys really matter or were they just a waste of time?
• In the flooded vessel complex I had a hard time bypassing a monster type with light dots scattered on his face. I decided “starface” would be a lovingly fitting name.
• Sometimes the game made me feel bad by turning off life support to a “human” connected up with fungus and electronics. At one point I even had to use a stun baton to zap a robot and get its chip.
• I liked the puzzle where I had to turn an antenna to match up lines on a radar panel in order to call a zeppelin. The rail track area itself was a bit confusing at first, though.
• Searching Catherine’s room (while she could comment on it from a computer panel in another room) brought a smile to my face. I bet she was secretly furious about it.
• The first attempt at entering the abyss was by using a vehicle called the DUNBAT, but when we finally found it, it had merged with human intelligence and agonizingly destroyed itself. Think Robocop.
• There was a cute part where we had to put the chip of a human consciousness into a computer, then also simulate his surroundings and his girlfriend. He wouldn’t calm down and give us info until then.
• That computer where modules had to be toggled and rebuilt really had me confuzzled at first. In hindsight I don’t even think it was a bad puzzle. Just… so very unexpected.
• In a maze of rooms, a “humpback” monster was roaming around. A computer could lock doors and I tried for a long time to lure it into a room. However, I think it was cheating with teleportation.
• In the meantime, I was stuck for too long in that maze because of not understanding how to plug a chip into a door panel. For some reason I didn’t catch at first that it had to sit behind two small levers.
• There was as a part in the game with a bit too many blind monsters around for my liking. I was afraid the rest of the game would then be like this, but luckily the developers backed out of it.
• Nice touch with those spheroid ocean floor cages.
• After collecting three important components, I had to sit in a chair and transfer my consciousness to a deep dive suit. This let to a duality problem with great philosophical implications. I loved that part.
• After a long elevator ride into the abyss, I had to follow blue lights in a “storm” of rivers featuring a big fish monster. When I finally got inside, the hero said, “Never been happier to be inside.” So very true.
• In the abyss complex, I met a roaming “oil human” that just followed me around in a creepy manner. I also found the very last human, a woman tied to a machine that I turned off. She asked me to do it.
• I found the ARK container and sent it away on a monorail. I tried to follow it but the corridor was blocked. I was stuck here for way too long before I found a small opening to a cave.
• This led to an organic “heart” where “starface” wanted me to put a hand into it and kill it. It’s was not even a boss fight, but it did eat my mechanical hand. Then “starface” got eaten by the fish monster.
• Another nice touch was how I climbed ladders with only one good hand. Lots of rung hugging.
• I sat in a chair, moved the ARK into a rocket tube, then launched it into space while transferring our consciousnesses to it. I think it was meant to gain speed through a tube all the way up to the surface.
• Then came another duality situation I probably should have anticipated coming. We were still left behind while our second selves were in the ARK too. Our hero was absolutely not happy. Bad ending.
• After the surprisingly short credits, a good ending had me in control of my ARK counterpart walking out of a cave and into grassy surroundings with birds singing – then finally meeting Catherine.