Overlays
Lists, menus, pickers, tooltips and toasts open in the top layer (Popover API), so cards, tables and scroll containers never clip them.
Placement
- Below the trigger, or above when there is not enough room; kept inside the viewport.
- Menus at the end of a row use
align="end". - Overlays reset inherited text styles, so a menu opened in a right-aligned cell stays left-aligned.
Closing
- Escape and a click outside close (light dismiss); focus returns to the trigger.
- Picking an item closes lists and menus;
kern-select multiplestays open.
Modals
kern-dialog (short confirmations, also via confirm()) and kern-drawer (details, filters, longer forms) are modal: the page behind is inert. kern-toast is not a modal and does not take focus.