I just want to remind everyone of this wonderfully simple guide to writing responsive web pages:
Just add
<meta name="viewport" content="width=device-width, initial-scale=1">
between the <head> and </head> tags.
That’s it! By default your page will be nonresponsive and broken on mobile devices’ small screens, but this one line fixes it.
https://motherfuckingwebsite.com/
To really show off, add some very basic styling for increased accessibility: