/* VARIABLES & RESET */
        :root {
            --primary: #2563eb;
            --primary-hover: #1d4ed8;
            --primary-light: #dbeafe;
            --bg-main: #f9fafb;
            --bg-secondary: #f3f4f6;
            --surface: #ffffff;
            --text-primary: #111827;
            --text-secondary: #6b7280;
            --text-tertiary: #9ca3af;
            --border: #e5e7eb;
            --success: #059669;
            --error: #dc2626;
            --radius-sm: 6px;
            --radius-md: 8px;
            --radius-lg: 12px;
            --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
            --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
            --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
            --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
            --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
        }

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

        html {
            scroll-behavior: smooth;
        }

        body {
            font-family: 'Inter', sans-serif;
            background-color: var(--bg-main);
            color: var(--text-primary);
            line-height: 1.6;
            -webkit-font-smoothing: antialiased;
            -moz-osx-font-smoothing: grayscale;
        }

        .container {
            max-width: 1280px;
            margin: 0 auto;
            padding: 0 20px;
        }

        /* HEADER */
        .header {
            background: var(--surface);
            border-bottom: 1px solid var(--border);
            position: sticky;
            top: 0;
            z-index: 100;
            box-shadow: var(--shadow-xs);
        }

        .header-inner {
            display: flex;
            justify-content: space-between;
            align-items: center;
            height: 72px;
        }

        .logo {
            display: flex;
            align-items: center;
            gap: 12px;
            text-decoration: none;
            font-size: 1.4rem;
            font-weight: 800;
            letter-spacing: -0.01em;
            color: var(--text-primary);
            transition: var(--transition);
        }

        .logo:hover {
            color: var(--primary);
        }

        .logo-icon {
            width: 36px;
            height: 36px;
            background: linear-gradient(135deg, var(--primary), #1d4ed8);
            border-radius: var(--radius-md);
            display: flex;
            align-items: center;
            justify-content: center;
            color: white;
        }

        .nav-links {
            display: flex;
            list-style: none;
            gap: 32px;
        }

        .nav-links a {
            text-decoration: none;
            color: var(--text-secondary);
            font-weight: 500;
            font-size: 0.95rem;
            transition: var(--transition);
            position: relative;
        }

        .nav-links a:hover {
            color: var(--primary);
        }

        .nav-links a::after {
            content: '';
            position: absolute;
            bottom: -4px;
            left: 0;
            width: 0;
            height: 2px;
            background: var(--primary);
            transition: width 0.2s;
        }

        .nav-links a:hover::after {
            width: 100%;
        }

        /* HERO SECTION */
        .hero {
            padding: 60px 0 80px;
        }

        .hero-content {
            text-align: center;
            max-width: 800px;
            margin: 0 auto;
        }

        .hero-badge {
            display: inline-block;
            background: var(--primary-light);
            color: var(--primary);
            font-size: 0.85rem;
            font-weight: 700;
            letter-spacing: 0.05em;
            padding: 8px 16px;
            border-radius: 20px;
            margin-bottom: 20px;
            text-transform: uppercase;
        }

        .hero h1 {
            font-size: 3.5rem;
            font-weight: 800;
            line-height: 1.1;
            letter-spacing: -0.02em;
            margin-bottom: 20px;
            color: var(--text-primary);
        }

        .hero p {
            font-size: 1.2rem;
            color: var(--text-secondary);
            line-height: 1.8;
            margin-bottom: 40px;
        }

        /* CONVERTER CARD */
        .converter-wrapper {
            background: var(--surface);
            border: 1px solid var(--border);
            border-radius: var(--radius-lg);
            box-shadow: var(--shadow-lg);
            overflow: hidden;
        }

        .converter-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 24px;
            border-bottom: 1px solid var(--border);
            flex-wrap: wrap;
            gap: 12px;
        }

        .file-info {
            font-size: 0.95rem;
            color: var(--text-secondary);
            font-weight: 500;
        }

        .converter-grid {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 0;
            min-height: 500px;
        }

        /* UPLOAD ZONE */
        .upload-zone {
            border-right: 1px solid var(--border);
            padding: 40px 30px;
            display: flex;
            align-items: center;
            justify-content: center;
            position: relative;
            transition: var(--transition);
        }

        .upload-zone.dragover {
            background: var(--primary-light);
        }

        .upload-input {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            opacity: 0;
            cursor: pointer;
        }

        .upload-content {
            text-align: center;
            pointer-events: none;
        }

        .upload-icon {
            width: 64px;
            height: 64px;
            margin: 0 auto 20px;
            background: var(--primary-light);
            border-radius: var(--radius-md);
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--primary);
        }

        .upload-content h3 {
            font-size: 1.3rem;
            font-weight: 700;
            margin-bottom: 8px;
            color: var(--text-primary);
        }

        .upload-content p {
            color: var(--text-secondary);
            font-size: 0.95rem;
            margin-bottom: 4px;
        }

        .upload-hint {
            color: var(--primary);
            font-weight: 600;
            text-decoration: underline;
        }

        .upload-formats {
            font-size: 0.85rem;
            color: var(--text-tertiary);
            margin-top: 16px;
        }

        .preview-area {
            text-align: center;
        }

        .preview-img {
            max-width: 100%;
            max-height: 320px;
            object-fit: contain;
            border-radius: var(--radius-md);
            box-shadow: var(--shadow-sm);
            margin-bottom: 16px;
        }

        .btn-change-file {
            background: var(--bg-secondary);
            border: 1px solid var(--border);
            padding: 8px 16px;
            border-radius: var(--radius-md);
            font-size: 0.9rem;
            font-weight: 600;
            cursor: pointer;
            color: var(--text-secondary);
            transition: var(--transition);
        }

        .btn-change-file:hover {
            background: var(--primary-light);
            color: var(--primary);
            border-color: var(--primary);
        }

        /* RESULT ZONE */
        .result-zone {
            padding: 24px;
            display: flex;
            flex-direction: column;
        }

        .result-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 16px;
        }

        .result-label {
            font-weight: 700;
            font-size: 0.95rem;
            color: var(--text-primary);
        }

        .result-actions {
            display: flex;
            gap: 8px;
        }

        .btn-result {
            background: var(--bg-secondary);
            border: 1px solid var(--border);
            padding: 6px 14px;
            border-radius: var(--radius-sm);
            font-size: 0.85rem;
            font-weight: 600;
            cursor: pointer;
            color: var(--text-secondary);
            transition: var(--transition);
            display: flex;
            align-items: center;
            gap: 6px;
        }

        .btn-result:hover:not(:disabled) {
            background: var(--primary-light);
            color: var(--primary);
            border-color: var(--primary);
        }

        .btn-result:disabled {
            opacity: 0.5;
            cursor: not-allowed;
        }

        .result-textarea {
            flex: 1;
            width: 100%;
            padding: 16px;
            border: 1px solid var(--border);
            border-radius: var(--radius-md);
            background: var(--bg-secondary);
            font-family: 'Fira Code', monospace;
            font-size: 0.9rem;
            line-height: 1.6;
            color: var(--text-primary);
            resize: none;
            outline: none;
            transition: var(--transition);
        }

        .result-textarea:focus {
            border-color: var(--primary);
            background: var(--surface);
            box-shadow: 0 0 0 3px var(--primary-light);
        }

        .result-textarea::-webkit-scrollbar {
            width: 8px;
        }

        .result-textarea::-webkit-scrollbar-track {
            background: transparent;
        }

        .result-textarea::-webkit-scrollbar-thumb {
            background: var(--border);
            border-radius: 4px;
        }

        .result-textarea::-webkit-scrollbar-thumb:hover {
            background: var(--text-tertiary);
        }

        /* PROGRESS OVERLAY */
        .progress-overlay {
            position: absolute;
            inset: 0;
            background: rgba(255, 255, 255, 0.98);
            backdrop-filter: blur(2px);
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            z-index: 20;
            border-radius: var(--radius-md);
        }

        .spinner {
            width: 48px;
            height: 48px;
            border: 3px solid var(--primary-light);
            border-top-color: var(--primary);
            border-radius: 50%;
            animation: spin 0.8s linear infinite;
            margin-bottom: 24px;
        }

        @keyframes spin {
            to { transform: rotate(360deg); }
        }

        .progress-text {
            font-size: 0.95rem;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 16px;
        }

        .progress-bar-track {
            width: 120px;
            height: 4px;
            background: var(--border);
            border-radius: 2px;
            overflow: hidden;
            margin-bottom: 12px;
        }

        .progress-bar-fill {
            height: 100%;
            background: var(--primary);
            width: 0%;
            transition: width 0.3s ease;
        }

        .progress-percent {
            font-size: 0.8rem;
            font-weight: 700;
            color: var(--text-secondary);
        }

        /* ACTION BAR */
        .converter-footer {
            padding: 24px;
            border-top: 1px solid var(--border);
            display: flex;
            justify-content: flex-end;
        }

        .btn-primary {
            background: var(--primary);
            color: white;
            border: none;
            padding: 12px 32px;
            border-radius: var(--radius-md);
            font-size: 1rem;
            font-weight: 600;
            cursor: pointer;
            transition: var(--transition);
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .btn-primary:hover:not(:disabled) {
            background: var(--primary-hover);
            transform: translateY(-2px);
            box-shadow: var(--shadow-md);
        }

        .btn-primary:disabled {
            background: var(--text-tertiary);
            cursor: not-allowed;
        }

        /* FEATURES SECTION */
        .features {
            padding: 100px 0;
            background: var(--surface);
            border-top: 1px solid var(--border);
        }

        .section-header {
            text-align: center;
            max-width: 600px;
            margin: 0 auto 60px;
        }

        .section-header h2 {
            font-size: 2.5rem;
            font-weight: 800;
            margin-bottom: 12px;
            color: var(--text-primary);
        }

        .section-header p {
            font-size: 1.1rem;
            color: var(--text-secondary);
        }

        .features-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
            gap: 32px;
        }

        .feature-card {
            padding: 32px;
            background: var(--bg-secondary);
            border: 1px solid var(--border);
            border-radius: var(--radius-lg);
            transition: var(--transition);
        }

        .feature-card:hover {
            border-color: var(--primary);
            box-shadow: var(--shadow-md);
        }

        .feature-icon {
            font-size: 2.5rem;
            margin-bottom: 16px;
        }

        .feature-card h3 {
            font-size: 1.2rem;
            font-weight: 700;
            margin-bottom: 12px;
            color: var(--text-primary);
        }

        .feature-card p {
            color: var(--text-secondary);
            font-size: 0.95rem;
            line-height: 1.7;
        }

        /* CONTENT SECTION */
        .content {
            padding: 80px 0;
        }

        .content-box {
            background: var(--surface);
            border: 1px solid var(--border);
            border-radius: var(--radius-lg);
            padding: 48px;
        }

        .content-box h2 {
            font-size: 2rem;
            font-weight: 800;
            margin-bottom: 24px;
            color: var(--text-primary);
        }

        .content-box h3 {
            font-size: 1.3rem;
            font-weight: 700;
            margin: 32px 0 16px;
            color: var(--text-primary);
        }

        .content-box p {
            color: var(--text-secondary);
            margin-bottom: 16px;
            line-height: 1.8;
            font-size: 1rem;
        }

        .content-box ol, .content-box ul {
            margin-left: 24px;
            margin-bottom: 20px;
            color: var(--text-secondary);
        }

        .content-box li {
            margin-bottom: 12px;
            line-height: 1.8;
        }

        .content-box strong {
            color: var(--text-primary);
            font-weight: 600;
        }

        /* FAQ SECTION */
        .faq {
            padding: 80px 0;
            background: var(--surface);
            border-top: 1px solid var(--border);
        }

        .faq-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
            gap: 32px;
        }

        .faq-item {
            padding: 28px;
            background: var(--bg-secondary);
            border: 1px solid var(--border);
            border-radius: var(--radius-lg);
        }

        .faq-item h4 {
            font-size: 1.1rem;
            font-weight: 700;
            margin-bottom: 12px;
            color: var(--text-primary);
        }

        .faq-item p {
            color: var(--text-secondary);
            font-size: 0.95rem;
            line-height: 1.7;
        }

        /* FOOTER */
        .footer {
            padding: 48px 0 32px;
            border-top: 1px solid var(--border);
            background: var(--bg-secondary);
        }

        .footer-content {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 24px;
            flex-wrap: wrap;
            gap: 20px;
        }

        .footer-brand {
            font-weight: 700;
            color: var(--text-primary);
        }

        .footer-links {
            display: flex;
            gap: 28px;
            list-style: none;
        }

        .footer-links a {
            text-decoration: none;
            color: var(--text-secondary);
            font-size: 0.9rem;
            transition: var(--transition);
        }

        .footer-links a:hover {
            color: var(--primary);
        }

        .footer-bottom {
            text-align: center;
            padding-top: 24px;
            border-top: 1px solid var(--border);
            color: var(--text-tertiary);
            font-size: 0.9rem;
        }

        /* TOAST */
        .toast {
            position: fixed;
            bottom: 24px;
            right: 24px;
            background: var(--text-primary);
            color: white;
            padding: 14px 20px;
            border-radius: var(--radius-md);
            font-weight: 500;
            font-size: 0.95rem;
            box-shadow: var(--shadow-lg);
            opacity: 0;
            transform: translateY(20px);
            pointer-events: none;
            transition: var(--transition);
            z-index: 1000;
        }

        .toast.show {
            opacity: 1;
            transform: translateY(0);
        }

        .hidden {
            display: none !important;
        }

        /* RESPONSIVE */
        @media (max-width: 768px) {
            .converter-grid {
                grid-template-columns: 1fr;
            }

            .upload-zone {
                border-right: none;
                border-bottom: 1px solid var(--border);
            }

            .hero h1 {
                font-size: 2.2rem;
            }

            .hero p {
                font-size: 1rem;
            }

            .nav-links {
                display: none;
            }

            .hero {
                padding: 40px 0 60px;
            }

            .footer-content {
                flex-direction: column;
                text-align: center;
            }

            .converter-content {
                gap: 20px;
            }
        }

        @media (prefers-reduced-motion: reduce) {
            * {
                animation-duration: 0.01ms !important;
                animation-iteration-count: 1 !important;
                transition-duration: 0.01ms !important;
            }
        }