Used media queries and grid for responsive design

I am proud of the fact that I was able to use grid and media queries for the responsive design because it definitely shortened my code and made the layout super simple. If I did this again, I would properly do research on the difference between rem and em because that threw me off a little bit. Also, I would like to figure out a way to make my code more "expandable" because having to manually assign separate background colors was probably not the most efficient way. Likely using CSS custom properties/ would help.

I at first found it difficult to understand the difference between rem and em because it seemed that they should have been the same, until I realized that I had set font sizes in many different places. Font-sizing is a skill that I need to work on as well since I often make it too small to fit everything on the page.