I'm not sure how much <details> can be customized, but there's also a CSS-only route using a hidden checkbox beneath the hamburger icon and looking for the inpu

I'm not sure how much <details> can be customized, but there's also a CSS-only route using a hidden checkbox beneath the hamburger icon and looking for the input[type="checkbox"]:checked selector. (Example: https://codepen.io/plavookac/pen/qomrMw https://codepen.io/plavookac/pen/qomrMw)