Hi this looks pretty good for me on mobile. Only a few small suggestions :
- if you change body to min- height instead of height the background won't suddenly cut off on mobile
- it's bad practice to jump heading levels, poor for both SEO and assistive technology. So make those headings into h2s instead
- I'd also recommend you swap to buttons to toggle your questions (inside the h2s). You can use inherit all in the css to style that button the same, and by using an interactive html element you get the bonus of making your solution instantly keyboard and assistive tech accessibile 🎉
Hope that helps ☺
2