QR-code using CSS And HTML Only

Working on mobile first is always the way to go. This project made me accept a life lesson: You don't have to be a rebel everytime; somethings work better if done as adviced. I rebelliously ignored the noble echoes of gurus to sometimes design for mobile first. After writing the code for desktop first, I instantly regreted it when I tried media query.

I picked up the good use of <img> tag.

Is it ok that I decided to give :root same color as container div for mobile design? It looked awkward have the container div ad grayish blue, card as white and toot background as white.