I can actually relate to this, Overtuned was made in around two days and a few hours because I had some college assignments to do. What an incredible piece of software allowing stuff like this to work in such a short amount of time, I was having fun but it definitely was not good for my health to not sleep to get it done.
There was some time spent outside of the engine conceptualizing what the game would be, but those moments were far in between while I was doing something else and an idea popped.