Age calculator app using HTML CSS and Javascript

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

I'm happy with how the design matches the specifications and the input validation. Next time I would think about the design and responsiveness from the start, instead of making it up as I go along.

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

The responsiveness was the part I found the most difficult. I worked it out with a bit of trial and error.

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

I used 'em' for responsive sizing, but it didn't work as easily as I thought, so maybe this wasn't the right approach?