I think I hit the three hour mark on this game the first time I sat down to play it. I've played it's predecessor Human Resource Machine and enjoyed that quite a bit so I'm not surprised I liked 7 Billion Humans as well. In these games you are an employee of a large corporation working your way up year after year. Each year is on a different level of the building and presents a new challenge. A few times along the way the path briefly splits off to give you some extra puzzles and these can be more difficult than the main branch.
Like Human Resource Machine, the game has you solve various puzzles by writing pseudo-code based on assembly, a low-level programming language. You click and drag various commands from a selection to form your program so you don't have to do any manual typing. However, if you wish to, you can actually type things by hand or copy and paste your existing code into a text editor. I thought this was pretty cool but only used it once or twice when I wanted to repeat large chunks of code.
I want to stop and say if you aren't interested in programming or have no knowledge or experience with it, don't let anything I've said so far scare you off of this game. You start with the basics, and new commands are presented to you slowly. I think some people would be surprised at how similar this feels to other single screen puzzle games like Toki Tori or Chuck's Challenge or Adventures of Lulu. I would also draw a comparison to Baba is You. Basically, if you like solving logic puzzles you will like this (and maybe also programming?).
Anyway, one of the main differences between Human Resource Machine and 7 Billion Humans is that in the latter you often control an entire crew of workers. So you have to build a solution which will work for everyone, since everyone will be running the same code. One of the ways to work around this is with IF statements, another difference from it's predecessor.
I found the overall challenge of the puzzles to be pretty high but not impossible. So far I have had to skip one or two that really have stumped me, but mostly I've been able to sort them out. There are two additional challenges for each level also, which are much harder, based on how efficient and how fast your program runs. These I was only able to obtain maybe 25% of the time. However, if you do pull it off, it can be very satisfying!
The last thing I want to talk about is the overall polish on this game. It looks great, the UI is simple and effective, and the sprites have their own quirky charm. There is lots of snark and humor in the dialog, and the levels are broken up by short cutscenes which give some story. I liked the sound effects and the intro music but I turned off the level music after a while. The only things I thought it lacked were subtitle options (for the cutscenes) and volume sliders, which were both oddly absent. I sort of got the impression this game was designed for mobile devices in mind, which is fine, it didn't detract from the gameplay.
I really enjoyed this one and I'll be coming back to finish it, if I can!
PS - It's really funny when one of your little workers kicks the bucket and also I had trouble narrowing it down to just 5 screenshots.