demo · v133
Menu bar cascade
A classic OS-style menu bar: top-level items reveal panels via interestfor, submenu items expand the next level. Hover, keyboard, or touch — the cascade behaves like every desktop menu you've ever used.
For full functionality (anchor positioning + nested popovers) Chrome 133+ is required. Without it the menus still open but the layout falls back to default top-left.
why not popovertarget alone?
popovertarget shows on click. interestfor shows on the broader “interest” signal — which for a menubar is exactly the behaviour you want: hover the parent, the panel slides in; tab through the menu, panels follow focus. Submenus can then nest the same attribute, and the UA handles the dismissal logic so panels close as soon as interest moves elsewhere.