E-commerce product page using flex-box (mobile first workflow)

This took me way longer than I expected. Writing code felt a bit tedious mainly because I didn't create many js functions. I tried my best to organize my CSS. I wrote about 800 lines of CSS on my first attempt just to get a barely good looking site which was not even responsive. So I deleted everything, took a break, watched some tutorials and tried mobile-first workflow and to my surprise, it actually turned out a lot better. I wish I knew this earlier. I also came out of my pixel cave and started using more of other units. This is also my first time writing this much js and it felt quite inefficient. I tried out so many new things in this challenge and overall, I learned a lot and I'm happy with what I got. I'd very much love to hear your feedback and suggestions on how I can improve things. Happy Coding!