Responsive Newsletter Signup Component with form validation

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

I'm pretty happy with the modal display in chrome, but I'm disappointed the transition doesn't seem to work in firefox. The mobile experience could probably be better, but I'm content with what's here.

Most of this was pretty easy to throw together, and I'm mostly happy with what I came up with.

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

The success modal on mobile gave me some grief. I've gotten more comfortable with flexbox, but it seems it's maybe not the best solution for that component. I'm happy with what I was able to get to work, but I'm disappointed it required some margin magic rather than being able to rely on align/justify settings.

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

Any feedback is appreciated!