Tip Calculator App (Mobile first, SCSS, vanilla JS)

I tried to implement these features / practices in the app:

• Use appropriate aria tags for accessibility.
• Debounce all the input fields' event handlers.
• Use Event delegation pattern for the tip percentage button events.
• Display error message (and also alert AT users) if the validation for an input field fails.
• Focus the first input element of the form when the reset button is used, for better accessibility.
• Data/State driven approach, i.e, state variables (captured in closures) are the single source of truth for the application's view layer.
• Follow POLE (Principle Of Least Exposure) using closures and the Classic Module Pattern.

Implementing all these was quite a challenge. Any feedback, code organisation in particular, is much appreciated. I'm also interested to know if there's any solution to this challenge that uses the class based approach. Thanks!