Order Summary Component (Flexbox + SASS)

Took a while but learnt a lot building this! Need to use more Mixins on SASS which I've included a few in this project.Would be worth it to learn how to utilize it more.

Originally, I set a Flexbox on the "container" code to align the main component center on the page. I wasn't able to put box-shadow on the main component for some reason, but after looking through codes on similarly centred websites, I decided to create its parent "card" and put Flex there. Then I put box-shadow on the container and it worked.

If someone can elaborate on why this is the case (box shadow not working on the div that has "Display: flex") I would appreciate it!

Also feedback on my codes would be apprectiated if there's anything I can improve on.