/* roulang page: index */
:root {
            --primary: #FF4D2E;
            --primary-hover: #E63E1F;
            --secondary: #1A1A2E;
            --accent: #00D4AA;
            --bg-light: #F8F9FC;
            --bg-white: #FFFFFF;
            --text-primary: #1A1A2E;
            --text-body: #4A4A5E;
            --text-muted: #8E8E9A;
            --text-light: #B0B0C0;
            --border-subtle: #E8E8F0;
            --radius-card: 12px;
            --radius-btn: 8px;
            --radius-input: 6px;
            --shadow-card: 0 2px 12px rgba(26, 26, 46, 0.06);
            --shadow-card-hover: 0 8px 24px rgba(26, 26, 46, 0.12);
            --shadow-btn-glow: 0 0 20px rgba(255, 77, 46, 0.4);
            --transition-fast: 0.2s ease;
            --transition-smooth: 0.3s ease;
            --font-stack-cn: "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", sans-serif;
            --font-stack-en: "Inter", "SF Pro Display", system-ui;
            --max-width: 1200px;
            --nav-height-desktop: 72px;
            --nav-height-mobile: 60px;
        }

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

        html {
            scroll-behavior: smooth;
        }

        body {
            font-family: var(--font-stack-cn);
            font-size: 16px;
            line-height: 1.7;
            color: var(--text-body);
            background-color: var(--bg-light);
            -webkit-font-smoothing: antialiased;
            -moz-osx-font-smoothing: grayscale;
            overflow-x: hidden;
        }

        body.nav-open {
            overflow: hidden;
        }

        .container {
            max-width: var(--max-width);
            margin: 0 auto;
            padding: 0 24px;
        }

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

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

        /* Navigation */
        .nav {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: var(--nav-height-desktop);
            background: rgba(255, 255, 255, 0.92);
            backdrop-filter: blur(12px);
            -webkit-backdrop-filter: blur(12px);
            z-index: 1000;
            transition: box-shadow var(--transition-smooth);
            display: flex;
            align-items: center;
        }

        .nav--scrolled {
            box-shadow: 0 1px 0 0 rgba(0, 0, 0, 0.06);
        }

        .nav-inner {
            display: flex;
            align-items: center;
            justify-content: space-between;
            width: 100%;
        }

        .nav-logo {
            font-size: 22px;
            font-weight: 700;
            color: var(--text-primary);
            white-space: nowrap;
            letter-spacing: -0.3px;
            display: flex;
            align-items: baseline;
            gap: 2px;
        }

        .nav-logo .logo-accent {
            color: var(--primary);
            font-size: 18px;
            font-weight: 700;
        }

        .nav-menu {
            display: flex;
            list-style: none;
            gap: 32px;
            align-items: center;
        }

        .nav-menu a {
            font-size: 15px;
            font-weight: 500;
            color: var(--text-body);
            padding: 8px 0;
            border-bottom: 2px solid transparent;
            transition: color var(--transition-fast), border-color var(--transition-fast);
        }

        .nav-menu a:hover,
        .nav-menu a.nav-active {
            color: var(--primary);
            border-bottom-color: var(--primary);
            font-weight: 600;
        }

        .nav-cta {
            display: inline-block;
        }

        .btn {
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 6px;
            font-weight: 600;
            border-radius: var(--radius-btn);
            cursor: pointer;
            transition: all var(--transition-smooth);
            border: 2px solid transparent;
            font-family: var(--font-stack-cn);
            white-space: nowrap;
            letter-spacing: 0.2px;
        }

        .btn--primary {
            background: var(--primary);
            color: #fff;
            padding: 12px 28px;
            font-size: 15px;
            box-shadow: var(--shadow-btn-glow);
        }

        .btn--primary:hover {
            background: var(--primary-hover);
            box-shadow: 0 0 28px rgba(255, 77, 46, 0.6);
            transform: scale(1.02);
        }

        .btn--primary:active {
            transform: scale(0.98);
        }

        .btn--outline {
            background: transparent;
            color: var(--primary);
            border-color: var(--primary);
            padding: 12px 28px;
            font-size: 15px;
        }

        .btn--outline:hover {
            background: var(--primary);
            color: #fff;
            transform: scale(1.02);
        }

        .btn--accent {
            background: var(--accent);
            color: var(--secondary);
            padding: 12px 28px;
            font-size: 15px;
        }

        .btn--accent:hover {
            opacity: 0.9;
            transform: scale(1.02);
        }

        .btn--large {
            padding: 18px 48px;
            font-size: 18px;
            border-radius: 12px;
        }

        .btn--white {
            background: #fff;
            color: var(--primary);
            border-color: transparent;
            font-weight: 700;
        }

        .btn--white:hover {
            background: #f0f0f0;
            transform: scale(1.02);
        }

        .btn--full {
            width: 100%;
        }

        /* Hamburger */
        .hamburger {
            display: none;
            flex-direction: column;
            justify-content: space-between;
            width: 28px;
            height: 20px;
            cursor: pointer;
            z-index: 1100;
            position: relative;
        }

        .hamburger span {
            display: block;
            width: 100%;
            height: 2.5px;
            background: var(--text-primary);
            border-radius: 2px;
            transition: all var(--transition-smooth);
            transform-origin: center;
        }

        .hamburger.active span:nth-child(1) {
            transform: translateY(8.5px) rotate(45deg);
        }

        .hamburger.active span:nth-child(2) {
            opacity: 0;
        }

        .hamburger.active span:nth-child(3) {
            transform: translateY(-8.5px) rotate(-45deg);
        }

        /* Hero Section */
        .hero {
            padding: calc(var(--nav-height-desktop) + 60px) 0 100px;
            background: var(--secondary);
            position: relative;
            overflow: hidden;
            color: #fff;
        }

        .hero::before {
            content: '';
            position: absolute;
            top: -20%;
            right: -10%;
            width: 60%;
            height: 140%;
            background: var(--primary);
            opacity: 0.08;
            transform: rotate(-15deg);
            border-radius: 40px;
        }

        .hero-geo {
            position: absolute;
            top: 10%;
            right: 5%;
            width: 500px;
            height: 500px;
            border: 2px solid rgba(255, 255, 255, 0.08);
            border-radius: 50%;
            pointer-events: none;
        }

        .hero-geo::after {
            content: '';
            position: absolute;
            top: 20%;
            left: 20%;
            width: 60%;
            height: 60%;
            border: 1.5px dashed rgba(255, 255, 255, 0.05);
            border-radius: 50%;
        }

        .hero .container {
            position: relative;
            z-index: 2;
            display: flex;
            align-items: center;
            gap: 60px;
        }

        .hero-content {
            flex: 1;
        }

        .hero-title {
            font-size: 48px;
            font-weight: 700;
            line-height: 1.2;
            letter-spacing: -0.5px;
            margin-bottom: 20px;
            color: #fff;
        }

        .hero-subtitle {
            font-size: 20px;
            line-height: 1.6;
            color: var(--text-light);
            margin-bottom: 40px;
            max-width: 480px;
        }

        .hero-buttons {
            display: flex;
            gap: 16px;
            flex-wrap: wrap;
        }

        .hero-image {
            flex: 1;
            text-align: center;
            position: relative;
        }

        .hero-image img {
            max-height: 420px;
            margin: 0 auto;
            border-radius: 24px;
        }

        /* Section Common */
        .section {
            padding: 100px 0;
        }

        .section-header {
            text-align: center;
            margin-bottom: 60px;
        }

        .section-title {
            font-size: 36px;
            font-weight: 700;
            color: var(--text-primary);
            margin-bottom: 16px;
            letter-spacing: -0.3px;
        }

        .section-desc {
            font-size: 18px;
            color: var(--text-muted);
            max-width: 600px;
            margin: 0 auto;
            line-height: 1.6;
        }

        /* Features Grid */
        .features-grid {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 24px;
        }

        .card {
            background: var(--bg-white);
            border-radius: var(--radius-card);
            padding: 36px 28px;
            box-shadow: var(--shadow-card);
            transition: all var(--transition-smooth);
            position: relative;
            overflow: hidden;
        }

        .card::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 3px;
            background: linear-gradient(90deg, var(--primary), var(--accent));
            opacity: 0;
            transition: opacity var(--transition-smooth);
        }

        .card:hover {
            transform: translateY(-6px);
            box-shadow: var(--shadow-card-hover);
        }

        .card:hover::before {
            opacity: 1;
        }

        .card-icon {
            width: 64px;
            height: 64px;
            margin-bottom: 20px;
            display: flex;
            align-items: center;
            justify-content: center;
            border-radius: 16px;
            background: #fff5f3;
            color: var(--primary);
            transition: transform var(--transition-smooth);
        }

        .card:hover .card-icon {
            transform: rotate(5deg);
        }

        .card-icon svg {
            width: 32px;
            height: 32px;
        }

        .card-title {
            font-size: 20px;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 12px;
        }

        .card-desc {
            font-size: 15px;
            color: var(--text-muted);
            line-height: 1.6;
        }

        /* Stats Section */
        .stats-section {
            background: var(--bg-light);
            padding: 80px 0;
        }

        .stats-grid {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 30px;
            text-align: center;
        }

        .stat-item {
            padding: 20px;
        }

        .stat-number {
            font-family: var(--font-stack-en);
            font-size: 56px;
            font-weight: 700;
            line-height: 1.1;
            background: linear-gradient(135deg, var(--primary), var(--accent));
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
            margin-bottom: 8px;
        }

        .stat-label {
            font-size: 15px;
            color: var(--text-muted);
            font-weight: 500;
        }

        /* Download Cards */
        .download-grid {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 24px;
        }

        .download-card {
            background: var(--bg-white);
            border-radius: var(--radius-card);
            padding: 40px 24px 32px;
            text-align: center;
            box-shadow: var(--shadow-card);
            transition: all var(--transition-smooth);
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        .download-card:hover {
            transform: translateY(-6px);
            box-shadow: var(--shadow-card-hover);
        }

        .download-card-img {
            width: 80px;
            height: 80px;
            margin-bottom: 20px;
            display: flex;
            align-items: center;
            justify-content: center;
            background: #fafafa;
            border-radius: 20px;
            overflow: hidden;
        }

        .download-card-img img {
            width: 100%;
            height: 100%;
            object-fit: cover;
        }

        .download-card-title {
            font-size: 20px;
            font-weight: 700;
            color: var(--text-primary);
            margin-bottom: 6px;
        }

        .download-card-meta {
            font-size: 13px;
            color: var(--text-muted);
            margin-bottom: 20px;
        }

        .download-card .btn {
            width: 100%;
        }

        /* Security Section */
        .security-grid {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 30px;
            text-align: center;
        }

        .security-item {
            padding: 30px 20px;
        }

        .security-icon {
            width: 80px;
            height: 80px;
            margin: 0 auto 20px;
            background: rgba(0, 212, 170, 0.1);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            color: var(--accent);
        }

        .security-icon svg {
            width: 40px;
            height: 40px;
        }

        .security-title {
            font-size: 20px;
            font-weight: 600;
            color: var(--text-primary);
            margin-bottom: 8px;
        }

        .security-desc {
            font-size: 15px;
            color: var(--text-muted);
        }

        /* FAQ Section */
        .faq-list {
            max-width: 800px;
            margin: 0 auto;
        }

        .faq-item {
            border-bottom: 1px solid var(--border-subtle);
        }

        .faq-question {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: 20px 0;
            cursor: pointer;
            font-size: 18px;
            font-weight: 600;
            color: var(--text-primary);
            gap: 16px;
            transition: color var(--transition-fast);
            user-select: none;
        }

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

        .faq-q-mark {
            width: 32px;
            height: 32px;
            background: var(--primary);
            color: #fff;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: 700;
            font-size: 16px;
            flex-shrink: 0;
        }

        .faq-toggle {
            width: 28px;
            height: 28px;
            border-radius: 50%;
            border: 2px solid var(--primary);
            color: var(--primary);
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 18px;
            transition: all var(--transition-fast);
            flex-shrink: 0;
        }

        .faq-item.active .faq-toggle {
            background: var(--primary);
            color: #fff;
        }

        .faq-answer {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.4s ease, padding 0.3s ease;
            padding: 0 0;
            color: var(--text-muted);
            font-size: 16px;
            line-height: 1.7;
        }

        .faq-item.active .faq-answer {
            max-height: 300px;
            padding: 0 0 24px 48px;
        }

        /* CTA Banner */
        .cta-banner {
            background: linear-gradient(135deg, var(--secondary) 0%, var(--primary) 100%);
            padding: 80px 0;
            text-align: center;
            color: #fff;
        }

        .cta-banner-title {
            font-size: 36px;
            font-weight: 700;
            margin-bottom: 16px;
        }

        .cta-banner-subtitle {
            font-size: 18px;
            opacity: 0.9;
            margin-bottom: 40px;
        }

        .cta-banner .btn {
            background: #fff;
            color: var(--primary);
            font-size: 20px;
            padding: 18px 56px;
            font-weight: 700;
        }

        /* Footer */
        .footer {
            background: var(--secondary);
            color: var(--text-muted);
            padding: 32px 0;
            font-size: 14px;
        }

        .footer-inner {
            display: flex;
            justify-content: space-between;
            align-items: center;
            flex-wrap: wrap;
            gap: 16px;
        }

        .footer-copy a {
            color: var(--text-light);
            text-decoration: underline;
            text-underline-offset: 3px;
        }

        .footer-social {
            display: flex;
            gap: 16px;
            list-style: none;
        }

        .footer-social a {
            display: flex;
            width: 36px;
            height: 36px;
            border: 1px solid var(--text-muted);
            border-radius: 50%;
            align-items: center;
            justify-content: center;
            color: var(--text-muted);
            transition: all var(--transition-fast);
            font-size: 16px;
        }

        .footer-social a:hover {
            border-color: #fff;
            color: #fff;
            background: rgba(255, 255, 255, 0.08);
        }

        /* Responsive */
        @media (max-width: 1024px) {
            .features-grid,
            .download-grid {
                grid-template-columns: repeat(2, 1fr);
            }

            .stats-grid {
                grid-template-columns: repeat(2, 1fr);
            }

            .hero .container {
                flex-direction: column;
                text-align: center;
            }

            .hero-content {
                order: 1;
            }

            .hero-image {
                order: 0;
            }

            .hero-buttons {
                justify-content: center;
            }

            .hero-title {
                font-size: 40px;
            }
        }

        @media (max-width: 768px) {
            body {
                font-size: 15px;
            }

            .nav {
                height: var(--nav-height-mobile);
            }

            .nav-menu {
                position: fixed;
                top: 0;
                left: 0;
                width: 100%;
                height: 100vh;
                background: #fff;
                flex-direction: column;
                justify-content: center;
                align-items: flex-start;
                padding: 0 32px;
                gap: 24px;
                transform: translateX(-100%);
                transition: transform var(--transition-smooth);
                z-index: 1050;
            }

            .nav-menu--open {
                transform: translateX(0);
            }

            .nav-menu a {
                font-size: 20px;
            }

            .nav-cta {
                display: none;
            }

            .hamburger {
                display: flex;
            }

            .hero {
                padding-top: calc(var(--nav-height-mobile) + 40px);
                padding-bottom: 60px;
            }

            .hero-title {
                font-size: 32px;
            }

            .hero-subtitle {
                font-size: 17px;
            }

            .hero-buttons {
                flex-direction: column;
                width: 100%;
            }

            .hero-buttons .btn {
                width: 100%;
            }

            .section {
                padding: 60px 0;
            }

            .section-title {
                font-size: 28px;
            }

            .features-grid,
            .download-grid {
                grid-template-columns: 1fr;
            }

            .security-grid {
                grid-template-columns: 1fr;
            }

            .stats-grid {
                grid-template-columns: 1fr 1fr;
                gap: 20px;
            }

            .stat-number {
                font-size: 40px;
            }

            .cta-banner-title {
                font-size: 28px;
            }

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

            .container {
                padding: 0 20px;
            }
        }

        @media (max-width: 520px) {
            .hero-title {
                font-size: 28px;
            }

            .section-title {
                font-size: 24px;
            }

            .card {
                padding: 24px 20px;
            }

            .stats-grid {
                grid-template-columns: 1fr;
            }

            .stat-number {
                font-size: 36px;
            }

            .cta-banner .btn {
                width: 100%;
                padding: 16px 24px;
                font-size: 18px;
            }
        }