What's a good UI for a zoom function?

1. What are the top 3 most important things in a good UI design?
2. What is the key to a good UI?

What are the top 3 most important things in a good UI design?

The UI design principals are:

Make it comfortable to interact with a product. Reduce cognitive load. Make user interfaces consistent.

What is the key to a good UI?

Consistency is key to UI design as it increases products' learnability. Good UI design comes from creating a sense of familiarity and ensuring that everything on a screen makes sense and works in ways that the user expects it to work.