QR Code Component with CSS

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

This is my first completed challenge from this website, and I am overall proud of everything, even though it's simple.

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

Without a minimum width, the container will shrink when changing the window size. Plus, it is better to use pixels rather than percentages for margins and other values since they are a fixed value and therefore are better when trying to ensure a fixed position.

If the margin of a container inside another container is bigger, the content will overflow. Margins have to be equal, or the container inside the other must have a smaller margin.

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

I would like help with everything code-related (especially CSS) and formatting. Is there a way to optimize my code? Is there any common beginner mistake I am committing?