Responsive Bento Grid With Grid and Flexbox

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

The part of which I am most proud is using only a few lines of code to make the page responsive. Although I usually struggle with making pages responsive, I managed to accomplish it using the grid and just a few lines on this complex page.

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

My challenge is bothersome. I added a fixed layout with flex to every box and placed it at the end of the code. As a result, there are some boxes whose flex attributes need to be modified. However, nothing changed after making the changes, so I had to go back and check the whole code until I found it.