media queries, responsive design, javasacript

I have already had some very positive feedback that will help me with future challenges. Particularly about not creating separate html code for mobile view, but rather use CSS to design for mobile. I realised my mistake when I noticed that my JavaScript code was not working whilst viewing on a mobile.

I now also understand the theory behind mobile first design, which is all about CSS and not HTML. (Correct me if I'm wrong)

Other than than that, please can I have some more feedback and advice on my attempt and code. I take everything on board and this will help me improve going forward.