The very first concept of the game was a goofy shitpost game about a frog that liked stabbing things. So, like, literally everything.
I scrapped way too many things, because for most of the game's development it was kind of just a hobby project that I figured only a handful of people would see, and I was inexperienced and intimidated by programming complicated systems. A really important change was early on, the Swamp area was a cave location with a bunch of cheery mining frog villagers. It really didn't work with the flow of the story. There was also a very unnecessary subplot with a really weird boss fight in the Copper City that was kind of a fun idea but really sidetracked the plot. One thing I somewhat regret scrapping was a cooking system. I think food's a small but pretty important part of Frogsong's worldbuilding, and I think Chorus cooking food out of dropped bug parts and plants harvested around the world would have been really cute. Maybe it wouldn't have added much mechanically but it would have been really cute!!!
I'm not sure if there's anything I'd say was weirdly time intensive, I knew going in most things would take longer than I wanted. One thing that did take quite a while was settling on how I wanted the frogs' architecture to look. The first version of the demo actually had completely different looking houses.
As for concepts/details I grew unexpectedly attached to, I'll hide this one because all of it is spoilers!

