Responsive landing page using flexbox

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

The exercise looks like very similar about the example of the frontend mentor page. In the next exercise I would like write with em and rem units in CSS, I think that way is the correct form to establish or write a good code.

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

I could centralized the card in the middle of the DOM. Previously in the last exercise I could'n because I didn't notice how to made it.

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

I need some suggest about how to write with em and rem units in css.