I made this in my own animation program that I'm developing. It's very smooth because it's vector based with automatic interpolation. It's a bit tricky to animate lines that aren't visible in every frame with that system though, and I didn't really have the tools to fix things coded at the time, so I just sort of stopped.

I think a good way to do it might be to make everything see-through like you'll see in the next animation. I'll work on layering strategies once I get coloring added in.