A total of maybe 2 hours (all of them).
I got a bit lazy with the bottom two, I was practically braindead by then, this stuff requires a lot of thinking. So ya know, it's also quite exhausting.
I'll most likely revisit the one on the top right. I was shamelessly inspired by Feng Zhu's new video he posted on youtube today, it's been at least 2 or 3 months since the last one so it got me incredibly excited.
Here is a somewhat finished version of the fortress one:[link]