* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            background: #f5f5f5;
            font-family: system-ui, -apple-system, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
            padding: 2rem 1.5rem;
            color: #222;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
        }

        /* brand header */
        .brand {
            margin-bottom: 1.5rem;
            display: flex;
            align-items: baseline;
            gap: 0.75rem;
            flex-wrap: wrap;
        }

        .brand h1 {
            font-weight: 450;
            font-size: 1.8rem;
            letter-spacing: -0.02em;
            color: #2a2a2a;
        }

        .brand .centrigon {
            font-weight: 500;
            color: #6b4f3f;
            background: #ede8e3;
            padding: 0.2rem 0.8rem;
            border-radius: 40px;
            font-size: 0.9rem;
        }

        .brand .tagline {
            color: #777;
            font-size: 0.95rem;
            font-weight: 350;
        }

        /* navigation */
        .nav-links {
            display: flex;
            gap: 0.5rem;
            margin-bottom: 2rem;
            background: white;
            padding: 0.6rem 1.2rem;
            border-radius: 60px;
            border: 1px solid #e0e0e0;
            width: fit-content;
            flex-wrap: wrap;
        }

        .nav-links a {
            text-decoration: none;
            color: #555;
            font-size: 0.85rem;
            padding: 0.3rem 1rem;
            border-radius: 30px;
            cursor: pointer;
            transition: all 0.2s;
        }

        .nav-links a.active {
            background: #222;
            color: white;
        }

        .nav-links a:hover {
            background: #f0f0f0;
            color: #222;
        }

        /* main layout */
        .summarizer-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 1.5rem;
            margin-bottom: 1.5rem;
        }

        @media (max-width: 768px) {
            .summarizer-grid {
                grid-template-columns: 1fr;
                gap: 1rem;
            }
        }

        .input-panel, .output-panel {
            background: white;
            border-radius: 20px;
            border: 1px solid #e0e0e0;
            overflow: hidden;
            display: flex;
            flex-direction: column;
        }

        .panel-header {
            padding: 1rem 1.25rem;
            background: #fafafa;
            border-bottom: 1px solid #e0e0e0;
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 0.5rem;
        }

        .panel-header h3 {
            font-size: 0.95rem;
            font-weight: 600;
            color: #444;
        }

        .stats-badge {
            font-size: 0.75rem;
            color: #888;
            background: #f0f0f0;
            padding: 0.2rem 0.7rem;
            border-radius: 20px;
        }

        textarea {
            width: 100%;
            min-height: 350px;
            padding: 1.25rem;
            border: none;
            font-family: 'SF Mono', 'Fira Code', monospace;
            font-size: 0.9rem;
            line-height: 1.6;
            resize: vertical;
            outline: none;
            background: white;
        }

        .output-content {
            padding: 1.25rem;
            min-height: 350px;
            max-height: 500px;
            overflow-y: auto;
            font-size: 0.95rem;
            line-height: 1.65;
            color: #333;
            background: white;
        }

        .output-content p {
            margin-bottom: 0.75rem;
        }

        .output-content .highlight-sentence {
            background: #fff3e0;
            border-left: 3px solid #6b4f3f;
            padding-left: 0.75rem;
            margin: 0.5rem 0;
        }

        /* controls */
        .controls-panel {
            background: white;
            border-radius: 20px;
            border: 1px solid #e0e0e0;
            padding: 1.25rem;
            margin-bottom: 1.5rem;
        }

        .control-group {
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            gap: 1.5rem;
            margin-bottom: 1rem;
        }

        .control-item {
            display: flex;
            align-items: center;
            gap: 0.75rem;
            flex-wrap: wrap;
        }

        .control-item label {
            font-size: 0.85rem;
            font-weight: 500;
            color: #555;
        }

        input[type="range"] {
            width: 200px;
            cursor: pointer;
        }

        .percent-value {
            background: #f0f0f0;
            padding: 0.2rem 0.8rem;
            border-radius: 30px;
            font-size: 0.85rem;
            font-weight: 600;
            color: #6b4f3f;
        }

        select {
            padding: 0.4rem 1rem;
            border-radius: 30px;
            border: 1px solid #ddd;
            background: white;
            font-size: 0.85rem;
            cursor: pointer;
        }

        .action-buttons {
            display: flex;
            gap: 0.75rem;
            flex-wrap: wrap;
            margin-top: 1rem;
            padding-top: 1rem;
            border-top: 1px solid #eee;
        }

        .btn {
            background: #f0f0f0;
            border: 1px solid #ddd;
            padding: 0.5rem 1.25rem;
            border-radius: 40px;
            font-size: 0.85rem;
            cursor: pointer;
            transition: all 0.2s;
            font-weight: 500;
        }

        .btn-primary {
            background: #6b4f3f;
            border-color: #6b4f3f;
            color: white;
        }

        .btn-primary:hover {
            background: #5a3e30;
        }

        .btn:hover {
            background: #e0e0e0;
        }

        /* extracted sentences preview */
        .sentences-preview {
            background: #fafafa;
            border-radius: 16px;
            padding: 1rem;
            margin-top: 0.75rem;
            font-size: 0.8rem;
            color: #666;
        }

        .sentences-preview span {
            display: inline-block;
            background: white;
            padding: 0.2rem 0.6rem;
            border-radius: 20px;
            margin: 0.2rem;
            font-size: 0.7rem;
            border: 1px solid #e0e0e0;
        }

        .toast {
            position: fixed;
            bottom: 30px;
            right: 30px;
            background: #222;
            color: white;
            padding: 0.6rem 1.5rem;
            border-radius: 40px;
            font-size: 0.9rem;
            opacity: 0;
            transition: opacity 0.15s;
            pointer-events: none;
            z-index: 1000;
        }

        .footer {
            margin-top: 3rem;
            text-align: center;
            color: #888;
            font-size: 0.8rem;
            border-top: 1px solid #ddd;
            padding-top: 2rem;
        }

        /* loading state */
        .loading {
            opacity: 0.6;
            pointer-events: none;
        }

        /* empty state */
        .empty-state {
            text-align: center;
            padding: 3rem;
            color: #aaa;
        }

        /* SEO Content */
        .seo-content {
            max-width: 1200px;
            margin: 2rem auto 0;
        }

        .seo-hero {
            background: white;
            border-radius: 20px;
            padding: 2rem;
            margin-bottom: 1.5rem;
            border: 1px solid #e8e8e8;
        }

        .seo-hero h2 {
            font-size: 1.6rem;
            font-weight: 600;
            color: #2a2a2a;
            margin-bottom: 1rem;
            padding-bottom: 0.5rem;
            border-bottom: 2px solid #6b4f3f;
            display: inline-block;
        }

        .seo-hero p {
            color: #444;
            line-height: 1.65;
            font-size: 1rem;
            margin-top: 1rem;
        }

        .seo-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
            gap: 1.5rem;
            margin-bottom: 1.5rem;
        }

        .seo-card {
            background: white;
            border-radius: 20px;
            padding: 1.5rem;
            border: 1px solid #e8e8e8;
            transition: box-shadow 0.2s ease;
        }

        .seo-card:hover {
            box-shadow: 0 4px 12px rgba(0, 0, 0, 0.04);
        }

        .feature-badge {
            display: inline-block;
            background: #ede8e3;
            color: #6b4f3f;
            font-size: 0.75rem;
            font-weight: 600;
            padding: 0.25rem 0.75rem;
            border-radius: 40px;
            margin-bottom: 1rem;
        }

        .seo-card h3 {
            font-size: 1.2rem;
            font-weight: 600;
            color: #2a2a2a;
            margin-bottom: 0.75rem;
        }

        .seo-card p {
            color: #444;
            line-height: 1.6;
            margin-bottom: 0.75rem;
            font-size: 0.95rem;
        }

        .seo-card ul {
            margin: 0.5rem 0 0.75rem 1.25rem;
            color: #444;
        }

        .seo-card li {
            margin-bottom: 0.4rem;
            font-size: 0.95rem;
        }

        .seo-card li strong {
            color: #6b4f3f;
        }

        .faq-q {
            font-weight: 600;
            color: #2a2a2a;
            margin-top: 1rem;
            margin-bottom: 0.25rem;
        }

        .faq-q:first-of-type {
            margin-top: 0;
        }

        .authority-line {
            background: #ede8e3;
            border-radius: 16px;
            padding: 1.25rem;
            text-align: center;
            margin-top: 1rem;
        }

        .visually-hidden {
            position: absolute;
            width: 1px;
            height: 1px;
            padding: 0;
            margin: -1px;
            overflow: hidden;
            clip: rect(0, 0, 0, 0);
            white-space: nowrap;
            border: 0;
        }

        @media (max-width: 768px) {
            .seo-hero {
                padding: 1.25rem;
            }
            .seo-hero h2 {
                font-size: 1.3rem;
            }
            .seo-card {
                padding: 1.25rem;
            }
        }