Tip Calculator App using basic HTML, CSS, and JS

I used radio inputs for the 5 fixed tip percentage selectors. I wanted to see if it was more efficient than using JS to add and remove classes from the selected value, but I ended up needing to add a class anyway because of the Custom percentage field. I was able to assign CSS values to the :checked state of the radio inputs, which was good to learn. Any tips or critiques on my methods are welcome. I'm always looking to learn and improve!