The Neon stars move based on two things.
1. Movement based on face Rotation.
2. Movement based on screen tap and drag
Add/Remove Neon stars
1. To add one star : Blink your eyes
2. To remove one star : Open your mouth
you will get an opportunity to learn shader code asset and how they work in spark AR.
This is very simple and pretty well managed code and graph patch that you will get. (Check out the demo image)
You can always enhance it to expand your imagination.
Delay frames, shader code asset, an amazing interactive project.