/* roulang page: index */
:root {
            --primary: #1E40AF;
            --primary-hover: #1D4ED8;
            --secondary: #0EA5E9;
            --accent: #10B981;
            --bg-light: #F8FAFC;
            --text-heading: #0F172A;
            --text-body: #334155;
            --text-muted: #64748B;
            --border-color: #E2E8F0;
            --radius-md: 0.75rem;
            --radius-xl: 1rem;
            --shadow-subtle: 0 4px 20px -2px rgba(15, 23, 42, 0.05);
            --shadow-hover: 0 20px 25px -5px rgba(15, 23, 42, 0.1), 0 8px 10px -6px rgba(15, 23, 42, 0.06);
        }

        html {
            scroll-behavior: smooth;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
            color: var(--text-body);
            background-color: #FFFFFF;
            line-height: 1.65;
            -webkit-font-smoothing: antialiased;
        }

        .custom-card {
            background-color: #FFFFFF;
            border: 1px solid #F1F5F9;
            box-shadow: var(--shadow-subtle);
            border-radius: var(--radius-xl);
            transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
        }

        .custom-card:hover {
            transform: translateY(-4px);
            box-shadow: var(--shadow-hover);
            border-color: #CBD5E1;
        }

        .nav-scrolled {
            background: rgba(255, 255, 255, 0.95);
            backdrop-filter: blur(12px);
            box-shadow: 0 4px 20px rgba(0, 0, 0, 0.06);
        }

        details summary::-webkit-details-marker {
            display: none;
        }

        details[open] summary .arrow-icon {
            transform: rotate(180deg);
        }

        .hero-bg {
            background: linear-gradient(135deg, rgba(30, 64, 175, 0.92) 0%, rgba(14, 165, 233, 0.85) 100%), url('/assets/images/fb33b895a4f5c37f.webp') center/cover no-repeat;
        }