Examples from W3Schools.com:

Example CSS from W3Schools - Blog Example #1
https://www.w3schools.com/w3css/w3css_templates.asp

Responsive Website Example #1
https://www.w3schools.com/howto/howto_js_topnav_responsive.asp

Responsive Website Example #2
This is my version of Example 1 with a lot of things taken out