/* roulang page: index */
:root {
            --primary: #F04E23;
            --primary-hover: #D03D1A;
            --secondary: #0F0F0F;
            --accent: #00C2FF;
            --accent-light: rgba(0, 194, 255, 0.1);
            --bg-light: #FAFAFA;
            --bg-dark: #0F0F0F;
            --text-dark: #1A1A1A;
            --text-gray: #555555;
            --text-light: #FFFFFF;
            --text-muted: #B0B0B0;
            --success: #00D68F;
            --danger: #FF3B30;
            --card-radius: 16px;
            --btn-radius: 10px;
            --input-radius: 8px;
            --container-radius: 20px;
            --shadow-sm: 0 2px 8px rgba(0,0,0,0.06);
            --shadow-hover: 0 12px 28px rgba(0,0,0,0.15), 0 0 0 1px rgba(240,78,35,0.1);
            --font-stack: 'PingFang SC', 'Microsoft YaHei', 'Hiragino Sans GB', 'Inter', system-ui, sans-serif;
            --transition: all 0.25s ease;
        }

        * {
            box-sizing: border-box;
        }

        html {
            scroll-behavior: smooth;
        }

        body {
            font-family: var(--font-stack);
            line-height: 1.7;
            background-color: var(--bg-light);
            color: var(--text-dark);
            margin: 0;
            padding: 0;
            -webkit-font-smoothing: antialiased;
            -moz-osx-font-smoothing: grayscale;
        }

        img {
            max-width: 100%;
            height: auto;
            display: block;
        }

        a {
            text-decoration: none;
            color: inherit;
            transition: var(--transition);
        }

        button, .btn {
            cursor: pointer;
            font-family: inherit;
            transition: var(--transition);
            border: none;
            outline: none;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 0.5rem;
            font-weight: 600;
        }

        input, textarea {
            font-family: inherit;
            transition: var(--transition);
            outline: none;
            border: 1px solid #ddd;
            border-radius: var(--input-radius);
            padding: 0.75rem 1rem;
            font-size: 1rem;
            width: 100%;
        }

        input:focus, textarea:focus {
            border-color: var(--accent);
            box-shadow: 0 0 0 3px var(--accent-light);
        }

        .container {
            max-width: 1280px;
            margin: 0 auto;
            padding: 0 2rem;
        }

        @media (max-width: 768px) {
            .container {
                padding: 0 1.25rem;
            }
        }

        /* Top Info Bar */
        .top-bar {
            background: var(--secondary);
            color: var(--text-muted);
            font-size: 0.8rem;
            height: 40px;
            display: flex;
            align-items: center;
            z-index: 50;
            position: relative;
        }

        .top-bar a {
            color: var(--text-muted);
        }

        .top-bar a:hover {
            color: var(--accent);
        }

        /* Main Nav */
        .main-nav {
            height: 72px;
            background: #fff;
            border-bottom: 1px solid #eee;
            display: flex;
            align-items: center;
            position: sticky;
            top: 0;
            z-index: 40;
            transition: var(--transition);
        }

        .brand-logo {
            font-size: 1.6rem;
            font-weight: 800;
            letter-spacing: -0.02em;
            color: var(--secondary);
            display: flex;
            align-items: center;
            gap: 0.25rem;
        }

        .brand-logo span.highlight {
            color: var(--primary);
        }

        .nav-links {
            display: flex;
            gap: 2.5rem;
            align-items: center;
            list-style: none;
            margin: 0;
            padding: 0;
        }

        .nav-links a {
            font-size: 0.95rem;
            font-weight: 500;
            color: #333;
            position: relative;
            padding: 0.25rem 0;
        }

        .nav-links a::after {
            content: '';
            position: absolute;
            bottom: -4px;
            left: 0;
            width: 0;
            height: 2px;
            background: var(--accent);
            transition: width 0.25s ease;
        }

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

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

        .hamburger {
            display: none;
            background: none;
            border: none;
            font-size: 1.8rem;
            color: var(--secondary);
            cursor: pointer;
        }

        /* Hero */
        .hero-section {
            background: var(--secondary);
            background-image: radial-gradient(circle at 30% 40%, rgba(240,78,35,0.08) 0%, transparent 50%),
                              linear-gradient(135deg, #1a1a1a 0%, #0F0F0F 100%);
            color: #fff;
            padding: 6rem 0 5rem;
            position: relative;
            overflow: hidden;
        }

        .hero-section::before {
            content: '';
            position: absolute;
            top: 0;
            right: 0;
            width: 50%;
            height: 100%;
            background: url('/assets/images/backpic/back-1.webp') center/cover no-repeat;
            opacity: 0.3;
            z-index: 1;
        }

        .hero-content {
            position: relative;
            z-index: 2;
        }

        .btn-primary {
            background: var(--primary);
            color: #fff;
            border-radius: var(--btn-radius);
            padding: 0.85rem 2rem;
            font-size: 1.05rem;
            box-shadow: 0 6px 20px rgba(240,78,35,0.3);
        }

        .btn-primary:hover {
            background: var(--primary-hover);
            transform: translateY(-2px);
            box-shadow: 0 12px 30px rgba(240,78,35,0.45);
        }

        .btn-secondary {
            background: transparent;
            border: 2px solid var(--accent);
            color: var(--accent);
            border-radius: var(--btn-radius);
            padding: 0.85rem 2rem;
            font-size: 1.05rem;
        }

        .btn-secondary:hover {
            background: var(--accent-light);
            border-color: #fff;
            color: #fff;
        }

        /* Metrics */
        .metric-card {
            background: #fff;
            border-radius: var(--card-radius);
            padding: 2rem 1.5rem;
            box-shadow: var(--shadow-sm);
            text-align: center;
            transition: var(--transition);
        }

        .metric-card:hover {
            box-shadow: var(--shadow-hover);
            transform: translateY(-4px);
        }

        .metric-number {
            font-size: 2.5rem;
            font-weight: 800;
            color: var(--accent);
            letter-spacing: -0.02em;
            line-height: 1.2;
        }

        .metric-unit {
            font-size: 1rem;
            font-weight: 600;
            color: var(--text-gray);
            margin-left: 0.2rem;
        }

        /* Service Cards */
        .service-card {
            background: rgba(255,255,255,0.03);
            border: 1px solid rgba(255,255,255,0.08);
            border-radius: var(--card-radius);
            padding: 2.2rem;
            transition: var(--transition);
            position: relative;
            backdrop-filter: blur(2px);
        }

        .service-card:hover {
            transform: translateY(-6px);
            border-color: rgba(0,194,255,0.4);
            box-shadow: 0 20px 35px rgba(0,0,0,0.5), 0 0 0 1px rgba(0,194,255,0.25);
        }

        .service-icon {
            font-size: 2.4rem;
            color: var(--primary);
            margin-bottom: 1.25rem;
            display: block;
        }

        /* Compare Section */
        .compare-bad {
            color: var(--danger);
            font-weight: 600;
        }

        .compare-good {
            color: var(--success);
            font-weight: 700;
        }

        /* FAQ Accordion */
        .faq-item {
            border-bottom: 1px solid #e0e0e0;
            padding: 1.2rem 0;
            cursor: pointer;
        }

        .faq-question {
            font-weight: 700;
            font-size: 1.1rem;
            display: flex;
            justify-content: space-between;
            align-items: center;
            color: var(--text-dark);
        }

        .faq-answer {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.4s ease, padding 0.3s ease;
            color: var(--text-gray);
            line-height: 1.7;
        }

        .faq-item.active .faq-answer {
            max-height: 220px;
            padding-top: 0.8rem;
        }

        .faq-item.active .faq-icon {
            transform: rotate(45deg);
            color: var(--accent);
        }

        .faq-icon {
            font-size: 1.5rem;
            font-weight: 300;
            transition: var(--transition);
            color: var(--text-gray);
        }

        /* Form */
        .contact-form-card {
            background: #fff;
            border-radius: var(--card-radius);
            padding: 2.5rem;
            box-shadow: 0 18px 35px rgba(0,0,0,0.08);
        }

        /* Footer */
        .footer {
            background: var(--secondary);
            color: var(--text-muted);
            padding: 4rem 0 2rem;
        }

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

        @media (max-width: 1024px) {
            .nav-links {
                gap: 1.5rem;
            }
        }

        @media (max-width: 768px) {
            .hamburger {
                display: block;
            }

            .nav-links {
                position: fixed;
                top: 72px;
                left: 0;
                width: 100%;
                height: 0;
                overflow: hidden;
                background: var(--secondary);
                flex-direction: column;
                gap: 0;
                transition: height 0.35s ease;
                z-index: 50;
            }

            .nav-links.open {
                height: calc(100vh - 72px);
                padding: 2rem 0;
            }

            .nav-links a {
                color: #fff;
                font-size: 1.2rem;
                padding: 1rem 0;
                display: block;
                text-align: center;
            }

            .hero-section {
                padding: 3.5rem 0 3rem;
            }

            .hero-section::before {
                width: 100%;
                opacity: 0.15;
            }

            .metric-card {
                padding: 1.5rem 1rem;
            }

            .service-card {
                padding: 1.8rem;
            }
        }

        @media (max-width: 520px) {
            .brand-logo {
                font-size: 1.3rem;
            }
            .btn-primary, .btn-secondary {
                width: 100%;
                justify-content: center;
            }
        }