:root{--bg-body:#f8fafc;--bg-sidebar:#fff;--bg-surface:#fff;--text-main:#0f172a;--text-muted:#64748b;--border-light:#e2e8f0;--primary:#3b82f6;--primary-hover:#2563eb;--accent-bg:#eff6ff;--pdf-bg:#cbd5e1;--danger:#ef4444;--shadow-md:0 4px 6px -1px #0000001a, 0 2px 4px -2px #0000001a;--shadow-floating:0 10px 25px -3px #0000001a, 0 4px 6px -4px #0000001a;--radius-md:8px;--radius-full:9999px}*{box-sizing:border-box}body,html{background-color:var(--bg-body);color:var(--text-main);width:100vw;height:100dvh;margin:0;padding:0;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;overflow:hidden}.app-layout{width:100%;height:100%;display:flex}.sidebar{background-color:var(--bg-sidebar);border-right:1px solid var(--border-light);z-index:10;flex-direction:column;flex-shrink:0;width:300px;transition:width .25s;display:flex;overflow:hidden}.sidebar.collapsed{width:44px}.sidebar.collapsed .sidebar-content,.sidebar.collapsed .class-manager,.sidebar.collapsed .brand{display:none}.sidebar.collapsed .sidebar-header{border-bottom:none;padding:8px}.sidebar.collapsed .sidebar-brand-row{justify-content:center}.sidebar-header{border-bottom:1px solid var(--border-light);padding:20px}.sidebar-brand-row{justify-content:space-between;align-items:center;margin-bottom:16px;display:flex}.brand{color:var(--primary);align-items:center;gap:10px;font-size:1.1rem;font-weight:700;display:flex}.class-manager{background:var(--bg-body);border-radius:var(--radius-md);border:1px solid var(--border-light);padding:12px}.class-row{align-items:center;gap:6px;margin-bottom:8px;display:flex}.class-select{border:1px solid var(--border-light);color:var(--text-main);background:#fff;border-radius:6px;flex-grow:1;padding:6px 10px;font-size:.85rem;font-weight:600}.btn-action-sm{border:1px solid var(--border-light);cursor:pointer;width:28px;height:28px;color:var(--text-muted);background:#fff;border-radius:6px;justify-content:center;align-items:center;font-size:.9rem;transition:all .2s;display:flex}.btn-action-sm:hover{border-color:var(--primary);color:var(--primary)}.btn-action-sm.delete:hover{border-color:var(--danger);color:var(--danger)}.sidebar-content{flex-grow:1;padding:12px;overflow-y:auto}.tree-root{margin:0;padding:0;list-style:none}.tree-node{padding-left:14px;list-style:none}.tree-label{border-radius:var(--radius-md);cursor:pointer;color:var(--text-muted);align-items:center;gap:8px;margin-bottom:2px;padding:8px 10px;font-size:.85rem;font-weight:500;transition:all .15s;display:flex}.tree-label:hover{background-color:var(--bg-body);color:var(--text-main)}.tree-label.active-file{background-color:var(--accent-bg);color:var(--primary);font-weight:600}.tree-label i{font-size:1.1rem}.folder-toggle-icon{margin-left:auto;transition:transform .2s;font-size:.75rem!important}.folder-collapsed .folder-toggle-icon{transform:rotate(-90deg)}.node-children{transition:all .2s}.hidden-branch{display:none!important}.inline-player{background:var(--bg-body);border:1px solid var(--border-light);border-radius:var(--radius-md);margin:2px 10px 8px;padding:8px 10px}.inline-player-row{align-items:center;gap:8px;display:flex}.inline-time{color:var(--text-muted);white-space:nowrap;font-family:monospace;font-size:.72rem;font-weight:600}.inline-video{background:#000;border-radius:6px;width:100%;max-height:160px;margin-bottom:6px;display:block}.main-workspace{background-color:var(--pdf-bg);flex-direction:column;flex-grow:1;display:flex;position:relative;overflow:hidden}.viewer-container{text-align:center;cursor:grab;touch-action:pan-x pan-y;flex-grow:1;padding:85px 20px 40px;position:relative;overflow:auto}.viewer-container.is-panning{cursor:grabbing}#pdf-canvas{box-shadow:var(--shadow-md);vertical-align:top;background:#fff;border-radius:4px;display:inline-block}.toolbar{background:var(--bg-surface);border-radius:var(--radius-full);box-shadow:var(--shadow-floating);z-index:50;border:1px solid var(--border-light);align-items:center;gap:16px;padding:8px 16px;display:flex;position:absolute;top:20px;left:50%;transform:translate(-50%)}.tool-group{align-items:center;gap:8px;display:flex}.divider{background-color:var(--border-light);width:1px;height:20px}.btn-icon{cursor:pointer;width:32px;height:32px;color:var(--text-muted);background:0 0;border:none;border-radius:50%;justify-content:center;align-items:center;font-size:1.1rem;transition:all .2s;display:flex}.btn-icon:hover{background-color:var(--bg-body);color:var(--text-main)}.btn-icon.active{background-color:var(--accent-bg);color:var(--primary)}.page-info{text-align:center;min-width:75px;font-size:.85rem;font-weight:600}.page-input{border:1px solid var(--border-light);text-align:center;width:60px;color:var(--text-main);background:#fff;border-radius:6px;padding:6px 8px;font-size:.9rem;font-weight:700}.loader-overlay{-webkit-backdrop-filter:blur(1px);backdrop-filter:blur(1px);z-index:100;background:#cbd5e199;flex-direction:column;justify-content:center;align-items:center;display:none;position:absolute;inset:0}.spinner{border:3px solid #3b82f64d;border-top-color:var(--primary);border-radius:50%;width:40px;height:40px;animation:.8s linear infinite spin}@keyframes spin{to{transform:rotate(360deg)}}.modal-overlay{-webkit-backdrop-filter:blur(2px);backdrop-filter:blur(2px);z-index:200;background:#0f172a66;justify-content:center;align-items:center;display:none;position:fixed;inset:0}.modal-box{background:var(--bg-surface);border-radius:var(--radius-md);box-shadow:var(--shadow-floating);border:1px solid var(--border-light);width:320px;padding:24px}.modal-title{color:var(--text-main);margin:0 0 16px;font-size:1.1rem}.modal-input{border:1px solid var(--border-light);border-radius:6px;outline:none;width:100%;margin-bottom:20px;padding:10px;font-size:.95rem}.modal-input:focus{border-color:var(--primary)}.modal-actions{justify-content:flex-end;gap:10px;display:flex}.btn-outline{border:1px solid var(--border-light);cursor:pointer;color:var(--text-muted);background:#fff;border-radius:6px;padding:8px 16px;font-weight:600}.btn-outline:hover{background:var(--bg-body);color:var(--text-main)}.btn-primary{background:var(--primary);cursor:pointer;color:#fff;border:none;border-radius:6px;padding:8px 16px;font-weight:600}.btn-primary:hover{background:var(--primary-hover)}.media-slider-track{appearance:none;border-radius:var(--radius-full);background:var(--border-light);cursor:pointer;outline:none;flex-grow:1;min-width:0;height:6px}.media-slider-track::-webkit-slider-thumb{appearance:none;background:var(--primary);cursor:pointer;border-radius:50%;width:14px;height:14px;transition:transform .1s,background-color .2s}.media-slider-track::-webkit-slider-thumb:hover{background:var(--primary-hover);transform:scale(1.25)}.fullscreen-nav{bottom:calc(36px + env(safe-area-inset-bottom,0px));z-index:10001;pointer-events:none;justify-content:space-between;align-items:center;padding:0 20px;display:none;position:fixed;left:0;right:0}.fullscreen-nav.visible{display:flex}.btn-fs-nav{pointer-events:all;color:#fff;cursor:pointer;-webkit-backdrop-filter:blur(8px);background:#0f172aa6;border:1px solid #fff3;border-radius:50%;justify-content:center;align-items:center;width:56px;height:56px;font-size:1.4rem;display:flex}.btn-fs-nav:active{background:#0f172ae6}.sidebar-backdrop{z-index:99;background:#0f172a73;display:none;position:fixed;inset:0}.sidebar-backdrop.visible{display:block}.btn-mobile-menu{z-index:50;background:var(--bg-surface);border:1px solid var(--border-light);border-radius:var(--radius-md);width:40px;height:40px;box-shadow:var(--shadow-floating);cursor:pointer;color:var(--text-muted);justify-content:center;align-items:center;font-size:1.2rem;display:none;position:absolute;top:16px;left:16px}@media (width<=640px){.sidebar{z-index:100;box-shadow:var(--shadow-floating);top:0;left:0;transform:translate(-100%);width:280px!important;height:100%!important;transition:transform .25s!important;position:fixed!important}.sidebar.mobile-open{transform:translate(0)}.sidebar.collapsed{width:280px!important;transform:translate(-100%)!important}.btn-mobile-menu{display:flex}.toolbar{top:auto;bottom:calc(16px + env(safe-area-inset-bottom,0px));z-index:60;max-width:calc(100vw - 32px);position:fixed;left:50%;transform:translate(-50%)}.viewer-container{padding:20px 12px 110px}}.main-workspace.is-fullscreen{z-index:9999;width:100vw!important;height:100vh!important;position:fixed!important;inset:0!important}