Styling menus can be a bit tricky as there a lot of variations to consider.
Active Link
Menus highlight the active menu trail and the active link.
Menu Twig Macro
Menus are rendered via a twig macro so submenus can be rendered.
https://api.drupal.org/api/drupal/core%21modules%21system%21templates%21menu.html.twig/9.2.x
Topics