Responsive Tip Calculator with Added Accessibility

Hi everyone, this is my first submission on FM. This is written with vanilla HTML, CSS3 and Javascript, no frameworks.

In addition to the base challenge, I tried to add a few extra features for accessibility. This solution adds a dark mode to the original design. I've also tried to make sure the site has working keyboard support. I would love any feedback on how to make this or similar projects more accessible. I'm also open to suggestions on how to better organize the code itself. Thank you!