Material Spinner - Principle File Attached

The other day I said this would be too difficult to make in principle, but I gave it a shot and surprised myself. It's not exactly like the material spinner, but I'm about to go home for the day so it's close enough. If you want the timings and easings to match perfectly, feel free to download the source file and have at it. Shouldn't take too much tweaking to get it perfect.

If you've not used principle before, check it out. I'm almost to the point where I'm using it all day, even more than sketch. Totally rocks my world. Also, let me know if you have any questions about the why and how I did this the way I did.