qr-code-component

I'm not sure if I was supposed to use things like Flexbox or Grid. Since I'm kind of new, I just did this project using stuff that I already know. What is the best way to style the main qr-code part with respect to the screen size? I think no matter how much I change it in my local machine, it comes out pretty different in the live page. So I was wondering why that is. Any help or code suggestions would be much appreciated.