/* ==================== 河马游戏SDK 企业级设计系统 ==================== */
:root {
    /* 主色系 - 品牌蓝 */
    --blue-600: #2563EB;
    --blue-700: #1D4ED8;
    --blue-50: #EFF6FF;
    --blue-100: #DBEAFE;

    /* 文字 */
    --text-primary: #0F172A;
    --text-secondary: #475569;
    --text-muted: #94A3B8;
    --text-inverse: #FFFFFF;

    /* 背景 */
    --bg-primary: #FFFFFF;
    --bg-secondary: #F8FAFC;
    --bg-tertiary: #F1F5F9;
    --bg-card: #FFFFFF;

    /* 边框 */
    --border: #E2E8F0;
    --border-light: #F1F5F9;
    --border-hover: #CBD5E1;

    /* 强调色 */
    --accent-purple: #8B5CF6;
    --accent-green: #10B981;
    --accent-amber: #F59E0B;
    --accent-rose: #F43F5E;
    --accent-cyan: #06B6D4;

    /* 渐变 */
    --gradient-1: linear-gradient(135deg, #2563EB, #7C3AED);
    --gradient-2: linear-gradient(135deg, #7C3AED, #DB2777);
    --gradient-3: linear-gradient(135deg, #059669, #06B6D4);
    --gradient-4: linear-gradient(135deg, #2563EB, #06B6D4);

    /* 阴影 */
    --shadow-xs: 0 1px 2px rgba(0, 0, 0, 0.04);
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06), 0 1px 2px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.08);

    /* 圆角 */
    --radius-sm: 8px;
    --radius: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --radius-2xl: 24px;

    /* 过渡 */
    --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; font-size: 16px; }

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

a { color: var(--blue-600); text-decoration: none; transition: var(--transition); }
a:hover { color: var(--blue-700); }

/* ===== 导航栏 ===== */
.nav {
    position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(12px); -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
}
.nav-inner {
    max-width: 1280px; margin: 0 auto;
    display: flex; align-items: center; justify-content: space-between;
    padding: 0 32px; height: 68px;
}
.nav-logo {
    display: flex; align-items: center; gap: 10px;
    font-size: 18px; font-weight: 700; color: var(--text-primary); letter-spacing: -0.3px;
}
.nav-logo .icon {
    width: 34px; height: 34px; border-radius: 8px;
    background: var(--blue-600);
    display: flex; align-items: center; justify-content: center;
    font-size: 16px; font-weight: 700; color: #fff;
}
.nav-logo img { height: 34px; width: auto; border-radius: 8px; object-fit: contain; }
.nav-links { display: flex; align-items: center; gap: 6px; list-style: none; }
.nav-links a {
    font-size: 14px; color: var(--text-secondary); font-weight: 500;
    padding: 8px 14px; border-radius: 8px; transition: var(--transition);
}
.nav-links a:hover { color: var(--text-primary); background: var(--bg-secondary); }
.nav-links a.active { color: var(--blue-600); background: var(--blue-50); }
.nav-cta {
    padding: 9px 22px; border-radius: 8px; border: none;
    background: var(--blue-600); color: #fff;
    font-size: 13px; font-weight: 600; cursor: pointer; transition: var(--transition);
}
.nav-cta:hover { background: var(--blue-700); color: #fff; transform: translateY(-1px); }
.nav-cta-outline {
    padding: 9px 22px; border-radius: 8px; border: 1px solid var(--border);
    background: transparent; color: var(--text-primary);
    font-size: 13px; font-weight: 600; cursor: pointer; transition: var(--transition);
}
.nav-cta-outline:hover { border-color: var(--blue-600); color: var(--blue-600); transform: translateY(-1px); }
.nav-actions { display: flex; align-items: center; gap: 8px; }
.nav-avatar {
    width: 32px; height: 32px; border-radius: 50%; flex-shrink: 0;
    display: flex; align-items: center; justify-content: center;
    background: var(--blue-600); color: #fff;
    text-decoration: none; cursor: pointer; transition: var(--transition);
    overflow: hidden;
}
.nav-avatar img { width: 100%; height: 100%; object-fit: cover; display: block; }
.nav-avatar svg { width: 18px; height: 18px; }
.nav-avatar:hover { transform: translateY(-1px); box-shadow: 0 4px 10px rgba(37,99,235,.3); }
.nav-toggle {
    display: none; position: relative; border: none; cursor: pointer;
    width: 32px; height: 32px; padding: 0; flex-shrink: 0;
    background: rgba(15, 23, 42, 0.08); border-radius: 10px;
    transition: background .2s, transform .15s;
}
.nav-toggle:active { transform: scale(0.94); background: var(--border); }
.nav-toggle span {
    display: block; position: absolute; left: 7px; right: 7px;
    height: 2.5px; border-radius: 3px; background: var(--text-primary);
    transition: transform .25s ease, opacity .2s ease, top .25s ease;
}
.nav-toggle span:nth-child(1) { top: 8px; }
.nav-toggle span:nth-child(2) { top: 14.75px; }
.nav-toggle span:nth-child(3) { top: 21.5px; }
.nav-toggle.active span:nth-child(1) { top: 14.75px; transform: rotate(45deg); }
.nav-toggle.active span:nth-child(2) { opacity: 0; }
.nav-toggle.active span:nth-child(3) { top: 14.75px; transform: rotate(-45deg); }

/* 移动端菜单内登录/注册入口（PC 端隐藏，菜单展开时显示） */
.m-nav-auth { display: none; }

/* ===== 容器与区块 ===== */
.container { max-width: 1280px; margin: 0 auto; padding: 0 32px; }
.section { padding: 120px 0; }

/* ===== Hero ===== */
.hero {
    padding: 180px 0 120px; text-align: center;
    position: relative; overflow: hidden;
}
.hero::before {
    content: '';
    position: absolute; top: -30%; left: 50%; transform: translateX(-50%);
    width: 800px; height: 800px;
    background: radial-gradient(circle, rgba(37, 99, 235, 0.06) 0%, transparent 60%);
    pointer-events: none;
}
.hero-badge {
    display: inline-flex; align-items: center; gap: 8px;
    padding: 6px 18px; border-radius: 100px;
    border: 1px solid var(--border); background: var(--bg-primary);
    font-size: 13px; color: var(--blue-600); font-weight: 500;
    margin-bottom: 32px;
}
.hero-badge .dot {
    width: 7px; height: 7px; border-radius: 50%;
    background: var(--accent-green);
    animation: pulse-dot 2s infinite;
}
.hero h1 {
    font-size: 56px; font-weight: 700; line-height: 1.12; letter-spacing: -1.5px;
    color: var(--text-primary); margin-bottom: 24px;
    max-width: 800px; margin-left: auto; margin-right: auto;
}
.hero h1 span { color: var(--blue-600); }
.hero p {
    font-size: 18px; color: var(--text-secondary); max-width: 640px;
    margin: 0 auto 40px; line-height: 1.7;
}
.hero-actions { display: flex; justify-content: center; gap: 14px; flex-wrap: wrap; align-items: center; }

/* ===== 按钮 ===== */
.btn {
    display: inline-flex; align-items: center; gap: 8px;
    padding: 13px 30px; border-radius: 10px; font-size: 15px; font-weight: 600;
    cursor: pointer; transition: var(--transition); border: none; text-decoration: none;
    white-space: nowrap;
}
.btn-primary { background: var(--blue-600); color: #fff; }
.btn-primary:hover { background: var(--blue-700); transform: translateY(-1px); box-shadow: 0 4px 16px rgba(37, 99, 235, 0.3); color: #fff; }
.btn-outline { background: var(--bg-primary); border: 1px solid var(--border); color: var(--text-primary); }
.btn-outline:hover { border-color: var(--blue-600); color: var(--blue-600); transform: translateY(-1px); }
.btn-ghost { background: transparent; border: none; color: var(--blue-600); padding: 13px 24px; }
.btn-ghost:hover { background: var(--blue-50); }
.btn-sm { padding: 9px 20px; font-size: 13px; border-radius: 8px; }
.btn-lg { padding: 16px 36px; font-size: 16px; border-radius: 12px; }

/* ===== 区段标题 ===== */
.section-label {
    display: inline-flex; align-items: center; gap: 10px;
    font-size: 13px; font-weight: 600; color: var(--blue-600);
    text-transform: uppercase; letter-spacing: 2px; margin-bottom: 16px;
}
.section-label::before { content: ''; width: 20px; height: 2px; background: var(--blue-600); border-radius: 2px; }
.section-title { font-size: 40px; font-weight: 700; letter-spacing: -0.8px; margin-bottom: 16px; color: var(--text-primary); }
.section-desc { font-size: 16px; color: var(--text-secondary); max-width: 600px; margin: 0 auto 56px; line-height: 1.7; }

/* ===== 基础卡片 ===== */
.card {
    background: var(--bg-card); border: 1px solid var(--border);
    border-radius: var(--radius-xl); padding: 36px 32px;
    transition: var(--transition-slow); position: relative; overflow: hidden;
}
.card:hover {
    border-color: var(--border-hover);
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}
.card-icon {
    width: 48px; height: 48px; border-radius: 12px;
    display: flex; align-items: center; justify-content: center; font-size: 22px;
    margin-bottom: 20px;
}
.card-icon.blue { background: rgba(37, 99, 235, 0.08); color: var(--blue-600); }
.card-icon.purple { background: rgba(139, 92, 246, 0.08); color: var(--accent-purple); }
.card-icon.green { background: rgba(16, 185, 129, 0.08); color: var(--accent-green); }
.card-icon.amber { background: rgba(245, 158, 11, 0.08); color: var(--accent-amber); }
.card-icon.rose { background: rgba(244, 63, 94, 0.08); color: var(--accent-rose); }
.card-icon.cyan { background: rgba(6, 182, 212, 0.08); color: var(--accent-cyan); }
.card h3 { font-size: 18px; font-weight: 600; margin-bottom: 8px; }
.card p { font-size: 14px; color: var(--text-secondary); line-height: 1.7; }

/* ===== 统计数字 ===== */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 0; }
.stat-item {
    text-align: center; padding: 32px 20px;
    border-right: 1px solid var(--border-light);
}
.stat-item:last-child { border-right: none; }
.stat-num { font-size: 44px; font-weight: 700; color: var(--blue-600); letter-spacing: -1px; }
.stat-label { font-size: 14px; color: var(--text-muted); margin-top: 4px; }

/* ===== Logo 墙 ===== */
.logo-wall {
    display: flex; align-items: center; justify-content: center; gap: 48px;
    flex-wrap: wrap; padding: 40px 0;
}
.logo-wall-item {
    height: 32px; opacity: 0.35; filter: grayscale(1);
    transition: var(--transition);
}
.logo-wall-item:hover { opacity: 0.7; filter: grayscale(0); }

/* ===== 客户证言 ===== */
.testimonial {
    text-align: center; max-width: 720px; margin: 0 auto; padding: 60px 0;
}
.testimonial blockquote {
    font-size: 20px; font-weight: 500; line-height: 1.7;
    color: var(--text-primary); margin-bottom: 28px;
}
.testimonial blockquote::before { content: '"'; }
.testimonial blockquote::after { content: '"'; }
.testimonial-author { display: flex; align-items: center; justify-content: center; gap: 12px; }
.testimonial-avatar {
    width: 44px; height: 44px; border-radius: 50%;
    background: var(--bg-tertiary); overflow: hidden;
}
.testimonial-name { font-size: 15px; font-weight: 600; }
.testimonial-role { font-size: 13px; color: var(--text-muted); }

/* ===== 图文交替区块 ===== */
.feature-row {
    display: grid; grid-template-columns: 1fr 1fr; gap: 80px; align-items: center;
    padding: 40px 0;
}
.feature-row.reverse { direction: rtl; }
.feature-row.reverse > * { direction: ltr; }
.feature-row-content h3 { font-size: 28px; font-weight: 700; margin-bottom: 16px; letter-spacing: -0.5px; }
.feature-row-content p { font-size: 16px; color: var(--text-secondary); line-height: 1.8; margin-bottom: 24px; }
.feature-row-content .feature-list { list-style: none; margin-bottom: 24px; }
.feature-row-content .feature-list li {
    font-size: 14px; color: var(--text-secondary); padding: 6px 0 6px 24px;
    position: relative; line-height: 1.6;
}
.feature-row-content .feature-list li::before {
    content: ''; position: absolute; left: 0; top: 13px;
    width: 6px; height: 6px; border-radius: 50%; background: var(--blue-600);
}
.feature-row-visual {
    background: var(--bg-secondary); border-radius: var(--radius-2xl);
    min-height: 360px; display: flex; align-items: center; justify-content: center;
    border: 1px solid var(--border);
}

/* ===== 两栏卡片布局 ===== */
.card-grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.card-grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.card-grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; }

/* ===== 对比表 ===== */
.compare-table { width: 100%; border-collapse: separate; border-spacing: 0; font-size: 14px; }
.compare-table thead th {
    padding: 18px 24px; text-align: left; border-bottom: 2px solid var(--border);
    font-weight: 600; color: var(--text-primary); background: var(--bg-secondary);
}
.compare-table thead th:first-child { border-radius: var(--radius-lg) 0 0 0; }
.compare-table thead th:last-child { border-radius: 0 var(--radius-lg) 0 0; }
.compare-table thead th.col-saas { color: var(--blue-600); }
.compare-table thead th.col-deploy { color: var(--accent-purple); }
.compare-table tbody td {
    padding: 16px 24px; border-bottom: 1px solid var(--border-light); color: var(--text-secondary);
}
.compare-table tbody tr:hover td { background: var(--blue-50); }
.compare-table tbody td:first-child { font-weight: 600; color: var(--text-primary); width: 180px; }

/* ===== 页面 Hero（子页面） ===== */
.page-hero { padding: 160px 0 80px; text-align: center; }
.page-hero h1 { font-size: 44px; font-weight: 700; letter-spacing: -1px; color: var(--text-primary); }
.page-hero p { font-size: 17px; color: var(--text-secondary); max-width: 600px; margin: 16px auto 0; line-height: 1.7; }

/* ===== CTA 区 ===== */
.cta-section { text-align: center; padding: 100px 0; }
.cta-section h2 { font-size: 36px; font-weight: 700; margin-bottom: 16px; letter-spacing: -0.5px; }
.cta-section p { font-size: 16px; color: var(--text-secondary); max-width: 560px; margin: 0 auto 32px; line-height: 1.7; }

/* ===== 底部 ===== */
.footer {
    background: var(--bg-secondary); border-top: 1px solid var(--border);
    padding: 64px 0 32px;
}
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 48px; }
.footer h4 { font-size: 14px; font-weight: 600; color: var(--text-primary); margin-bottom: 20px; }
.footer a, .footer p { font-size: 14px; color: var(--text-muted); display: block; margin-bottom: 10px; transition: var(--transition); }
.footer a:hover { color: var(--text-primary); }
.footer-bottom { margin-top: 48px; padding-top: 24px; border-top: 1px solid var(--border); text-align: center; font-size: 13px; color: var(--text-muted); }

/* ===== 标签 ===== */
.tag {
    display: inline-flex; align-items: center; gap: 4px;
    padding: 4px 12px; border-radius: 100px;
    font-size: 12px; font-weight: 600;
}
.tag.blue { background: var(--blue-50); color: var(--blue-600); }
.tag.purple { background: rgba(139, 92, 246, 0.08); color: var(--accent-purple); }
.tag.green { background: rgba(16, 185, 129, 0.08); color: var(--accent-green); }
.tag.amber { background: rgba(245, 158, 11, 0.08); color: var(--accent-amber); }

/* ===== 动画 ===== */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(24px); }
    to { opacity: 1; transform: translateY(0); }
}
@keyframes pulse-dot {
    0%, 100% { opacity: 1; transform: scale(1); }
    50% { opacity: 0.5; transform: scale(1.3); }
}
.animate { animation: fadeInUp 0.6s ease both; }

/* ===== 响应式 ===== */
@media (max-width: 1024px) {
    .hero h1 { font-size: 42px; }
    .section-title { font-size: 32px; }
    .stats { grid-template-columns: repeat(2, 1fr); }
    .stat-item:nth-child(2) { border-right: none; }
    .footer-grid { grid-template-columns: 1fr 1fr; }
    .feature-row { grid-template-columns: 1fr; gap: 40px; }
    .card-grid-4 { grid-template-columns: repeat(2, 1fr); }
    .card-grid-3 { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 768px) {
    .container { padding: 0 20px; }
    .nav-inner { padding: 0 20px; height: 60px; gap: 5px; }
    .nav-links { display: none; }
    .nav-toggle { display: block; }
    .nav-logo { font-size: 16px; }
    .nav-logo .icon { width: 30px; height: 30px; font-size: 14px; border-radius: 7px; }
    .nav-links.open {
        display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px;
        position: absolute; top: 60px; left: 0; right: 0;
        background: rgba(255, 255, 255, 0.98); backdrop-filter: blur(12px);
        border-bottom: 1px solid var(--border); padding: 14px 16px 16px;
        box-shadow: var(--shadow-md);
        animation: navDrop .25s ease;
        max-height: calc(100vh - 60px); overflow-y: auto;
    }
    @keyframes navDrop {
        from { opacity: 0; transform: translateY(-8px); }
        to   { opacity: 1; transform: translateY(0); }
    }
    .nav-links.open > li { display: flex; }
    .nav-links.open > li:not(.m-nav-auth) a {
        flex: 1; display: flex; align-items: center; justify-content: center;
        padding: 14px 6px; font-size: 14px; font-weight: 500;
        border-radius: 10px; background: var(--bg-card);
        border: 1px solid var(--border); box-shadow: var(--shadow-xs);
        color: var(--text-primary); text-decoration: none;
        white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
        transition: background .15s, color .15s, border-color .15s, transform .15s;
    }
    .nav-links.open > li:not(.m-nav-auth) a:active { transform: scale(0.96); }
    .nav-links.open > li:not(.m-nav-auth) a:hover { background: var(--blue-50); color: var(--blue-600); border-color: var(--blue-600); }
    .nav-links.open > li:not(.m-nav-auth) a.active { background: var(--blue-600); color: #fff; border-color: var(--blue-600); box-shadow: 0 2px 8px rgba(37,99,235,.25); }

    /* 顶部隐藏登录/注册按钮，移入下拉菜单 */
    .nav-actions .nav-cta, .nav-actions .nav-cta-outline { display: none; }
    /* 手机端：头像靠右、紧挨汉堡按钮 */
    .nav-actions { margin-left: auto; }
    .nav-links.open .m-nav-auth {
        grid-column: 1 / -1; order: 99;
        display: flex; gap: 10px; padding: 12px 0 2px; margin: 10px 0 0;
        border-top: 1px solid var(--border); border-bottom: none;
    }
    .nav-links.open .m-nav-auth a {
        flex: 1; text-align: center; padding: 12px 0; border-radius: 10px;
        font-size: 14px; font-weight: 600; text-decoration: none;
    }
    .m-nav-auth .auth-login,
    .m-nav-auth .auth-user { background: var(--blue-50); color: var(--blue-600); }
    .m-nav-auth .auth-reg { background: var(--blue-600); color: #fff; }
    .m-nav-auth .auth-logout { background: transparent; color: var(--text-muted); border: 1px solid var(--border); }
    .hero { padding: 140px 0 80px; }
    .hero h1 { font-size: 34px; }
    .hero p { font-size: 15px; }
    .section { padding: 72px 0; }
    .section-title { font-size: 28px; }
    .section-desc { font-size: 14px; margin: 0 auto 36px; }
    .page-hero { padding: 140px 0 60px; }
    .page-hero h1 { font-size: 30px; }
    .stats { grid-template-columns: 1fr 1fr; }
    .stat-item { padding: 20px 12px; }
    .stat-num { font-size: 32px; }
    .footer-grid { grid-template-columns: repeat(3, 1fr); gap: 12px 16px; }
    .footer-grid > div:first-child { grid-column: 1 / -1; }
    .footer h4 { font-size: 12px; margin-bottom: 8px; }
    .footer a, .footer p { font-size: 12px; margin-bottom: 4px; }
    .footer-grid > div:first-child p { display: none; }
    .card-grid-2, .card-grid-3, .card-grid-4 { grid-template-columns: 1fr; }
    .feature-row-visual { min-height: 220px; }
    .btn-lg { padding: 14px 28px; font-size: 14px; }
}
@media (max-width: 480px) {
    .container { padding: 0 16px; }
    .nav-inner { padding: 0 16px; height: 56px; }
    .nav-actions { gap: 6px; }
    .nav-cta, .nav-cta-outline { padding: 7px 14px; font-size: 12px; }
    .hero { padding: 120px 0 60px; }
    .hero h1 { font-size: 28px; letter-spacing: -0.5px; }
    .hero p { font-size: 14px; -webkit-line-clamp: 2; display: -webkit-box; -webkit-box-orient: vertical; overflow: hidden; }
    .section { padding: 56px 0; }
    .section-title { font-size: 24px; letter-spacing: -0.3px; }
    .section-desc { font-size: 13px; -webkit-line-clamp: 2; display: -webkit-box; -webkit-box-orient: vertical; overflow: hidden; }
    .page-hero { padding: 120px 0 48px; }
    .page-hero h1 { font-size: 24px; }
    .page-hero p { font-size: 14px; -webkit-line-clamp: 2; display: -webkit-box; -webkit-box-orient: vertical; overflow: hidden; }
    .stats { grid-template-columns: 1fr; }
    .stat-item { border-right: none; border-bottom: 1px solid var(--border-light); padding: 24px 16px; }
    .stat-item:last-child { border-bottom: none; }
    .stat-num { font-size: 28px; }
    .stat-label { font-size: 12px; }
    .footer { padding: 48px 0 24px; }
    .footer-bottom { margin-top: 32px; }
    .btn { padding: 11px 22px; font-size: 13px; }
    .btn-lg { padding: 13px 24px; font-size: 14px; }
    .feature-row { gap: 24px; }
    .feature-row-visual { min-height: 200px; }
    .card { padding: 24px 20px; }
    .logo-wall { gap: 24px; padding: 24px 0; }
    .logo-wall-item { height: 24px; }
}

/* ================================================================
   移动端内容精简（仅 ≤768px 生效，PC 端不受影响）
   用法：
   - class="m-hide"                  手机端隐藏（纯装饰/低决策价值）
   - <details class="fold-block">    手机端折叠块（PC 端始终展开）
       <summary>标题 <span class="fold-arrow">▾</span></summary>
       <div class="fold-body">内容</div>
     </details>
   ================================================================ */
@media (max-width: 768px) {
    .m-hide { display: none !important; }
}

/* 折叠块通用样式 */
.fold-block summary {
    list-style: none; cursor: pointer;
    display: flex; justify-content: space-between; align-items: center;
    padding: 14px 16px; font-size: 15px; font-weight: 600; color: var(--text-primary);
}
.fold-block summary::-webkit-details-marker { display: none; }
.fold-arrow { font-size: 11px; color: var(--text-muted); transition: transform .2s; }
.fold-block[open] .fold-arrow { transform: rotate(180deg); }

@media (min-width: 769px) {
    /* PC 端：始终展开，不显示折叠头 */
    .fold-block summary { display: none; }
    .fold-block:not([open]) > .fold-body { display: block !important; }
}

@media (max-width: 768px) {
    /* 移动端：折叠成卡片 */
    .fold-block {
        border: 1px solid var(--border); border-radius: 12px;
        background: var(--bg-card); overflow: hidden; margin-bottom: 14px;
    }
    .fold-block[open] summary { display: none; }
    .fold-body { padding: 14px 16px; }
    /* 展开后恢复显示内容原有标题，避免与折叠标题重复 */
    .fold-block[open] .sec-hd { display: block; margin-bottom: 14px; }
}