No, you're not going to get me addicted to Factorio again. I won't let you!
Ah man, there's so much to like here. I dig the chill soundtrack so much. I want more tracks like this. You've got such a nice variety of machines here, the look is clean, the puzzles scale up well in difficulty and you're right on for the theme. The UI has some nice flourishes I noticed, like the scene change.
I'm going to nitpick a couple things now, mostly in the UI, so get ready. I suggest right-clicking allows me to drop a machine I'm holding, or the eraser. I think clicking on a machine should make it "stick" to my cursor so I can drop it that way if I prefer, right-click returning it to the tray in order to place belts. I think erasing a machine maybe shouldn't erase the belts too, but I'm not sure about that one. I'd like to be able to move already-placed buildings within the grid. I'd make the operation start running as soon as there's a belt path running from the start to all end goals, just for a satisfying little moment there. And I don't know if its compatible with your code base, but being able to make changes while the operation is running would be rad and help with clarity. I'd also change up the Level Complete screen so players can watch their glorious operation produce for a moment.
Okay, that's a lot of nitpicking, but only because I think you should develop this a little further and find the right platform to release it on. Find those Zachtronics players and make them your players! Well done, superb entry.