bs-shell is a responsive app-shell layout with a collapsible sidebar. The sidebar is projected via the bsShellSidebar attribute directive (sets slot="sidebar"); all other children form the main content area. The [state] input ('auto', 'show', 'hide') controls visibility, while [breakpoint] sets the viewport size at which 'auto' reveals the sidebar. setSize() on the component instance lets you resize it at runtime.