Tip Calculator App(OOP's,Class Inheritance,Mobile First,Validation)

What are you most proud of, and what would you do differently next time?

Apart from a basic approach, this app is designed using Javascript Prototype Inheritance, OOP's,etc.

What challenges did you encounter, and how did you overcome them?

• Passing properties between classes
• Input Field Validation

What specific areas of your project would you like help with?

• I would kindly request the expert reviewers to go through my work and you are always welcome to provide me any improvement feedback for my approach of designing the classes. Should it have been better or more optimized, or if there is some other better easy way.
• Any UI design, styling, responsiveness improvements.
• I would really appreciate any of your suggestions and feedback as it will be valuable for my learning.