Responsive Tip Calculator App with SASS and React.js

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

Currently studying React JS library. I'm proud of finishing this project with using exactly what I learned so far.

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

One of the challenges I encountered was "lifting state up", which turned out to not be so complicated, at least in this small app.

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

Don't need any help right now, but I would like to know if there is something wrong with my code, maybe some best practises that I didn't use here.