Responsive landing page in CSS

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

Making the site responsive is one of the many improvements I am proud of having made. I want to create a challenge more quickly the next time.

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

Well, challenges I faced were quit easy; by researching the article again and again, I managed it.

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

Well, while reading about media queries in part of the grid section, I was not able to use grid-gap and box-shadow: var(--generic-shadow). May I know why?