:root{--bg:#f4f4f5;--surface:#ffffff;--surface-hover:#fafafa;--border:#e4e4e7;--border-strong:#d4d4d8;--text:#18181b;--text-muted:#71717a;--text-soft:#a1a1aa;--orange:#f36b21;--orange-soft:#fff4ed;--orange-ring:rgba(243,107,33,0.15);--sidebar-w:300px;--radius:12px;--radius-sm:8px;--shadow-sm:0 1px 2px rgba(0,0,0,0.04);--shadow-md:0 4px 24px rgba(0,0,0,0.06)}*{box-sizing:border-box}body,html{margin:0;min-height:100%;background:var(--bg);color:var(--text);font-family:system-ui,-apple-system,Segoe UI,Roboto,Helvetica Neue,Arial,sans-serif;font-size:15px;line-height:1.5;-webkit-font-smoothing:antialiased}a{color:inherit;text-decoration:none}button,input{font:inherit}.app-shell{display:flex;min-height:100vh}.main-panel{flex:1 1;min-width:0;overflow:auto}.panel-empty,.panel-loading{display:grid;place-items:center;min-height:60vh;color:var(--text-muted);padding:40px}.panel-content{max-width:960px;padding:32px 40px 64px}.panel-header h1{margin:6px 0 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span{display:block;color:var(--text-soft);font-size:12px;font-weight:600;text-transform:uppercase;letter-spacing:.04em}.lesson-meta-card strong{display:block;margin-top:6px;font-size:14px;line-height:1.45}.lesson-block{margin-bottom:24px}.lesson-block h3{margin:0 0 12px;font-size:15px;font-weight:650}.lesson-list{margin:0;padding-left:20px;color:var(--text-muted);font-size:14px;line-height:1.55}.lesson-list li+li{margin-top:8px}.lesson-table-wrap{overflow:auto;border:1px solid var(--border);border-radius:var(--radius-sm);background:var(--surface)}.lesson-table{width:100%;border-collapse:collapse;font-size:13px}.lesson-table td,.lesson-table th{padding:12px 14px;border-bottom:1px solid var(--border);vertical-align:top;text-align:left}.lesson-table th{background:var(--bg);font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:.03em;color:var(--text-muted)}.lesson-table tr:last-child td{border-bottom:0}.lesson-table td code{font-size:12px;background:var(--orange-soft);padding:2px 6px;border-radius:4px}.lesson-table-flow td:first-child{white-space:nowrap;font-weight:600;color:var(--text)}.lesson-details{margin-bottom:12px;border:1px solid var(--border);border-radius:var(--radius-sm);background:var(--surface)}.lesson-details summary{cursor:pointer;padding:14px 16px;font-weight:650;font-size:14px}.lesson-details[open] summary{border-bottom:1px solid var(--border)}.lesson-markdown{padding:16px}.lesson-paragraph{margin:0 0 12px;color:var(--text-muted);font-size:14px;line-height:1.55}.lesson-raw-pre{margin:0;padding:16px;overflow:auto;max-height:480px;background:#18181b;color:#e4e4e7;font-size:12px;line-height:1.55;white-space:pre-wrap;word-break:break-word}.compare-note,.lesson-empty{color:var(--text-muted);font-size:14px}.compare-note{margin:0 0 16px}.compare-table-wrap{overflow:auto;border:1px solid var(--border);border-radius:var(--radius-sm);background:var(--surface)}.compare-table{width:100%;border-collapse:collapse;font-size:13px}.compare-table td,.compare-table th{padding:14px 16px;border-bottom:1px solid var(--border);vertical-align:top;text-align:left}.compare-table th{background:var(--bg);font-size:12px;font-weight:700;text-transform:uppercase;letter-spacing:.03em;color:var(--text-muted)}.compare-table td:first-child{width:48px;color:var(--text-soft);font-weight:700}.compare-table td strong{display:block;font-size:14px;margin-bottom:4px}.compare-table td p{margin:0;color:var(--text-muted);line-height:1.5}.compare-time{display:block;margin-bottom:6px;color:var(--text-soft);font-size:12px}.compare-missing{color:var(--text-soft);font-style:italic}.compare-row-warn{background:#fffbeb}@media (max-width:900px){.lesson-meta-grid{grid-template-columns:1fr}.lesson-section-head{flex-direction:column}.deck-view-tabs{width:100%;flex-wrap:wrap}}