:root{--bg: #f8fafc;--panel: #ffffff;--ink: #1f2937;--muted: #6b7280;--accent: #2563eb;--accent-hover: #1d4ed8;--ok: #16a34a;--warn: #b45309;--danger: #dc2626;--border: #e6e8f0}*{box-sizing:border-box}html,body,#root{height:100%}body{margin:0;font-family:ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Helvetica,Arial,Apple Color Emoji,Segoe UI Emoji;color:var(--ink);background:var(--bg)}.app-shell{min-height:100%;display:grid;grid-template-rows:auto 1fr auto}.app-header{display:flex;align-items:center;justify-content:space-between;padding:12px 16px;border-bottom:1px solid var(--border);background:#fff;position:sticky;top:0;z-index:10;box-shadow:0 1px 2px #0000000a}.brand{color:var(--ink);font-weight:700;letter-spacing:.2px;text-decoration:none}.top-nav a{color:var(--muted);margin-right:12px;text-decoration:none}.top-nav a.active{color:var(--ink)}.btn{background:#fff;color:var(--ink);border:1px solid var(--border);border-radius:8px;padding:10px 14px;cursor:pointer;text-decoration:none;transition:background-color .15s ease,box-shadow .15s ease,transform .05s ease}.btn.primary{background:var(--accent);color:#fff;border-color:var(--accent)}.btn.ghost{background:transparent;border-color:var(--border)}.btn:disabled{opacity:.6;cursor:not-allowed}.btn:hover:not(:disabled){background:#f9fafb;box-shadow:0 1px 2px #0000000f}.btn.primary:hover:not(:disabled){background:var(--accent-hover);border-color:var(--accent-hover);box-shadow:0 2px 6px #2563eb40}.btn:active:not(:disabled){transform:translateY(.5px)}.app-main{padding:16px}.app-footer{padding:16px;color:var(--muted);border-top:1px solid var(--border);background:#fff}.panel{background:var(--panel);border:1px solid var(--border);border-radius:12px;padding:16px}.stack{display:grid;gap:12px}.row{display:flex;gap:12px;align-items:center;flex-wrap:wrap}.field{display:grid;gap:6px}.field label{color:var(--muted);font-size:12px;font-weight:600}.input,select,textarea{background:#fff;color:var(--ink);border:1px solid var(--border);border-radius:8px;padding:12px 14px}textarea{min-height:120px}.grid{display:grid;gap:12px}.grid.cards{grid-template-columns:repeat(auto-fill,minmax(260px,1fr))}.badge{display:inline-block;padding:2px 10px;border-radius:999px;font-size:12px;border:1px solid var(--border);color:var(--muted);background:#fff}.toolbar{display:flex;justify-content:space-between;align-items:center;margin-bottom:12px}.tabs{display:flex;gap:8px;border-bottom:1px solid var(--border);margin-bottom:12px}.tabs a{padding:10px 12px;text-decoration:none;color:var(--muted);border-bottom:3px solid transparent;border-radius:6px 6px 0 0}.tabs a.active{color:var(--ink);border-color:var(--accent)}.tabs a:hover{background:#f2f6ff;color:#1f2937}.list{display:grid;gap:8px}.item{display:grid;gap:8px;padding:14px;border:1px solid var(--border);background:#fff;border-radius:10px}.muted{color:var(--muted)}.help{font-size:12px;color:var(--muted)}.title{font-weight:700;font-size:18px}.subtitle{color:var(--muted)}.grow{flex:1 1 auto;min-width:280px}.breadcrumbs{color:var(--muted);font-size:13px}@media (max-width: 640px){.app-main{padding:8px}}.course-shell{display:grid;grid-template-columns:300px 1fr;gap:16px}.course-sidebar{background:#fff;border:1px solid var(--border);border-radius:12px;padding:12px;position:sticky;top:64px;height:calc(100vh - 96px);overflow:auto}.course-sidebar-header{display:grid;gap:4px;margin-bottom:8px}.course-title{font-weight:700;font-size:16px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.course-title-link{color:inherit;text-decoration:none}.course-title-link:hover{text-decoration:underline}.course-subtitle{color:var(--muted);font-size:12px}.outline{display:grid;gap:6px}.outline-item{display:grid;gap:4px}.outline-row{display:flex;align-items:center;gap:6px}.chevron{border:0;background:transparent;padding:0 4px;cursor:pointer;color:var(--muted)}.outline-link{display:flex;align-items:center;gap:8px;padding:8px 10px;border-radius:8px;color:var(--ink);text-decoration:none;border:1px solid transparent;transition:background-color .15s ease,border-color .15s ease}.outline-link.active{background:#f4f7ff;border-color:#e0e7ff;color:#102a43}.outline-link:hover{background:#f8fafc;border-color:var(--border)}.outline-children{display:grid;gap:4px;margin-left:20px}.outline-link.child{color:var(--muted)}.sidebar-actions{margin-top:12px}.course-content{display:grid;gap:8px}.course-header{display:flex;justify-content:space-between;align-items:flex-start;background:var(--panel);border:1px solid var(--border);border-radius:12px;padding:16px}.course-header-left{display:grid;gap:4px}.course-body{display:grid;gap:12px}@media (max-width: 1024px){.course-shell{grid-template-columns:1fr}.course-sidebar{position:relative;height:auto}}