I love how similar our games are in terms of mechanics! You need to teach us how you did the "hold temperature between certain degrees", we were originally planning on doing that but couldn't figure out a way to do it within the timeframe!
I love how you have designed this game. On my first playthrough, I was multitasking trying to keep the temp going while building the parts and it was a lot of fun switching between the two. However on my second playthrough, I realised I didn't actually have to do them simultaneously which was a bit of a disappointment. I could work on 1 task and finish the other one later. I think it'd be great if you had implemented a way so you can't build the part (click space) until the temp was within the zone. It would've added just a nice little layer on top of what you had already! (in my opinion)
Otherwise, great game! Espeically for your first Godot game and being solo!