Four card feature section

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

I'm proud because I think that I had good approach when building responsive layouts, I can't think of what I would do differently next time.

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

My main challenge here was grid, because I'm not using that often. I know how it works, but had some trouble remembering and putting right width/height for columns and rows. I overcame them with help of Google :D

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

Overall review of code and if it can be improved or optimized.