Responsive qr-code card using pure CSS

Hi everyone,

It is an easy project but I want to improve my code : what are your advices in term of clean code, performance and other things ?

I used only pure CSS and pure html without any framework or librairies.

happy to hear from you.

Why I add normalize.css : it is used to begin with a css that will behave the right way but it is not meant for this type of tiny project as it is too heavy, 70% of its rules are not used here. I try it on this small project to see what it can do by curiosity.

If the project would scale, do you think it is a good idea to add this or it is too heavy and bad for performance ?