What problem does it solve? Building a consistent, collapsible sidebar across multiple static HTML pages requires rewriting the same CSS, HTML, and JavaScript each time, and small mistakes (like overflow conflicts or lost collapse state) break the layout. This Skill provides a complete, copy-paste-ready sidebar component with section collapsing, full sidebar collapse, mobile drawer mode, and localStorage state persistence. ## Core Features & Use Cases - Section Group Collapse: Each sidebar section toggles open/closed via a button, with state remembered per group using unique data-id keys in localStorage. - Full Sidebar Collapse & Mobile Drawer: Desktop users can collapse the entire sidebar to a floating expand pill; on screens under 768px the sidebar becomes a slide-in drawer with a backdrop overlay. - Use Case: When adding a new page to the TRACKER dashboard suite, paste the provided CSS, HTML skeleton, and JS into the page, assign unique data-id values per the naming convention, and the page immediately has a working collapsible sidebar consistent with the rest of the site. ## Quick Start Add a collapsible sidebar to my TRACKER HTML page using the rsun-sidebar component with the standard TRACKER and projects groups.