/* Speeduino ECU — 深色主题样式（多彩版） */
:root {
    --bg-base:      #0f1117;   /* 最深背景 */
    --bg-card:      #1a1d27;   /* 卡片/侧边栏背景 */
    --bg-elevated:  #22263a;   /* 略高层级背景 */
    --border:       #2e3248;   /* 分隔线 */

    --accent:       #d4b86a;   /* 暗调金黄（主强调） */
    --accent-dim:   #b09a55;   /* 更暗一档的黄 */
    --accent-blue:  #7ab8f5;   /* 浅蓝（次强调） */
    --accent-cyan:  #5ee7df;   /* 青色点缀 */
    --accent-purple:#c792ea;   /* 紫色点缀 */
    --accent-pink:  #f78c6c;   /* 橙粉点缀 */
    --accent-green: #7ee787;   /* 柔和绿 */
    --accent-red:   #f07178;   /* 柔和红 */

    --text-primary: #eef0f8;   /* 主文字 */
    --text-muted:   #8b90a8;   /* 次要文字 */
    --text-dim:     #555b78;   /* 更暗提示文字 */

    --white: #ffffff;
}

/* ========== 全局重置 ========== */
* { margin: 0; padding: 0; box-sizing: border-box; }

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI',
                 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: var(--bg-base);
    color: var(--text-primary);
    line-height: 1.6;
}

a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--white); }

/* ========== 导航栏 ========== */
.navbar {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    position: fixed;
    top: 0; left: 0; right: 0;
    z-index: 1000;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 64px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--accent);
}

.logo-icon {
    width: 36px; height: 36px;
    background: var(--accent);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--bg-base);
    font-weight: 900;
    font-size: 1.1rem;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 6px;
}

.nav-menu a {
    display: block;
    padding: 6px 14px;
    border-radius: 6px;
    color: var(--text-muted);
    font-size: 0.95rem;
    font-weight: 500;
    transition: color .15s, background .15s;
}

.nav-menu a:hover { color: var(--text-primary); background: var(--bg-elevated); }
.nav-menu a.active { color: var(--accent); background: var(--bg-elevated); }

/* 二级菜单样式 */
.nav-menu .dropdown {
    position: relative;
}

.nav-menu .dropdown-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 8px;
    min-width: 180px;
    padding: 8px 0;
    box-shadow: 0 4px 12px rgba(0,0,0,0.3);
    z-index: 1000;
    margin-top: 4px;
}

.nav-menu .dropdown-menu a {
    padding: 10px 16px;
    border-radius: 0;
    font-size: 0.9rem;
    white-space: nowrap;
}

.nav-menu .dropdown:hover .dropdown-menu {
    display: block;
}

.nav-menu .dropdown > a::after {
    content: ' ▼';
    font-size: 0.7rem;
    opacity: 0.6;
}

/* 移动端菜单按钮 */
.menu-toggle {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 5px;
}
.menu-toggle span {
    width: 22px; height: 2px;
    background: var(--text-muted);
}

/* ========== 通用布局 ========== */
main { margin-top: 64px; min-height: calc(100vh - 64px); }

.page-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 48px 24px;
}

/* 页头 */
.page-header {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    padding: 52px 24px;
    text-align: center;
}
.page-header h1 { font-size: 2rem; color: var(--accent); margin-bottom: 10px; }
.page-header p  { color: var(--text-muted); font-size: 1rem; }

/* section标题 */
.section-title { text-align: center; margin-bottom: 52px; }
.section-title h2 { font-size: 1.75rem; color: var(--accent); margin-bottom: 10px; }
.section-title p  { color: var(--text-muted); }

/* ========== 按钮 ========== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 7px;
    padding: 10px 24px;
    border-radius: 6px;
    font-weight: 600;
    font-size: 0.95rem;
    cursor: pointer;
    border: none;
    transition: opacity .15s;
}
.btn:hover { opacity: .85; }

.btn-primary  { background: var(--accent);      color: var(--bg-base); }
.btn-secondary{ background: var(--bg-elevated); color: var(--text-primary); border: 1px solid var(--border); }
.btn-accent   { background: var(--accent-blue); color: var(--white); }

/* ========== HERO ========== */
.hero {
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    padding: 90px 24px 80px;
    text-align: center;
}
.hero-content { max-width: 720px; margin: 0 auto; }
.hero h1 { font-size: 2.6rem; font-weight: 800; line-height: 1.25; margin-bottom: 18px; }
.hero h1 span { color: var(--accent); }
.hero p  { font-size: 1.1rem; color: var(--text-muted); margin-bottom: 36px; }
.hero-buttons { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }

/* ========== 通用卡片 ========== */
.card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 28px;
}

/* ========== 特性网格 ========== */
.features { padding: 72px 24px; }
.features-grid {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 20px;
}
.feature-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 28px 24px;
}
.feature-icon {
    font-size: 1.75rem;
    margin-bottom: 14px;
}
.feature-card h3 { font-size: 1rem; color: var(--accent); margin-bottom: 10px; }
.feature-card p  { color: var(--text-muted); font-size: 0.9rem; line-height: 1.7; }

/* ========== ECU平台卡片 ========== */
.ecu-types { padding: 0 24px 72px; }
.ecu-grid {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
    gap: 20px;
}
.ecu-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    overflow: hidden;
}
.ecu-image {
    height: 140px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3rem;
    background: var(--bg-elevated);
    border-bottom: 1px solid var(--border);
}
.ecu-content { padding: 24px; }
.ecu-content h3 { font-size: 1.2rem; color: var(--accent); margin-bottom: 8px; }
.ecu-content p  { color: var(--text-muted); font-size: 0.9rem; margin-bottom: 16px; }
.ecu-tags { display: flex; flex-wrap: wrap; gap: 7px; margin-bottom: 18px; }
.tag {
    background: var(--bg-elevated);
    border: 1px solid var(--border);
    padding: 3px 10px;
    border-radius: 4px;
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* ========== 手册布局 ========== */
.manual-container {
    display: grid;
    grid-template-columns: 240px 1fr;
    gap: 28px;
    max-width: 1300px;
    margin: 0 auto;
    padding: 36px 24px;
}
.manual-sidebar {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 20px;
    height: fit-content;
    position: sticky;
    top: 80px;
}
.manual-sidebar h3 {
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: .08em;
    color: var(--text-dim);
    margin-bottom: 14px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--border);
}
.manual-nav { list-style: none; }
.manual-nav a {
    display: block;
    padding: 8px 12px;
    color: var(--text-muted);
    border-radius: 6px;
    font-size: 0.88rem;
    transition: color .12s, background .12s;
    margin-bottom: 2px;
}
.manual-nav a:hover { color: var(--text-primary); background: var(--bg-elevated); }
.manual-nav a.active { color: var(--accent); background: var(--bg-elevated); }

.manual-content {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 36px 40px;
    min-width: 0;
}
.manual-chapter { display: none; }
.manual-chapter.active { display: block; }

.manual-content h2 {
    font-size: 1.6rem;
    color: var(--accent);
    margin-bottom: 24px;
    padding-bottom: 14px;
    border-bottom: 1px solid var(--border);
}
.manual-content h3 {
    font-size: 1.15rem;
    color: var(--accent-blue);
    margin: 32px 0 14px;
}
.manual-content h4 {
    font-size: 1rem;
    color: var(--text-primary);
    margin: 22px 0 10px;
}
.manual-content p  { color: var(--text-muted); margin-bottom: 14px; line-height: 1.8; font-size: 0.95rem; }
.manual-content ul,
.manual-content ol { color: var(--text-muted); padding-left: 22px; margin-bottom: 16px; font-size: 0.95rem; }
.manual-content li { margin-bottom: 7px; line-height: 1.7; }

.manual-content code {
    background: var(--bg-elevated);
    color: var(--accent);
    padding: 2px 7px;
    border-radius: 4px;
    font-family: 'Consolas','Cascadia Code',monospace;
    font-size: 0.88em;
}
.manual-content pre {
    background: var(--bg-base);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 18px 20px;
    overflow-x: auto;
    margin: 16px 0;
}
.manual-content pre code {
    background: none;
    color: var(--text-primary);
    padding: 0;
    font-size: 0.88rem;
}

/* 表格 */
.manual-content table,
.product-table,
.param-table {
    width: 100%;
    border-collapse: collapse;
    margin: 18px 0;
    font-size: 0.9rem;
}
.manual-content th,
.manual-content td,
.product-table th,
.product-table td,
.param-table th,
.param-table td {
    padding: 10px 14px;
    text-align: left;
    border-bottom: 1px solid var(--border);
}
.manual-content th,
.product-table th,
.param-table th {
    background: var(--bg-elevated);
    color: var(--accent);
    font-size: 0.82rem;
    text-transform: uppercase;
    letter-spacing: .05em;
}
.manual-content td,
.product-table td,
.param-table td { color: var(--text-muted); }
.manual-content tr:hover td,
.param-table tr:hover td { background: var(--bg-elevated); color: var(--text-primary); }

/* 提示框 */
.warning-box {
    background: rgba(245,216,122,.08);
    border-left: 3px solid var(--accent);
    padding: 14px 18px;
    margin: 18px 0;
    border-radius: 0 6px 6px 0;
    font-size: 0.9rem;
    color: var(--text-muted);
}
.warning-box strong { color: var(--accent); }

.info-box {
    background: rgba(91,156,246,.08);
    border-left: 3px solid var(--accent-blue);
    padding: 14px 18px;
    margin: 18px 0;
    border-radius: 0 6px 6px 0;
    font-size: 0.9rem;
    color: var(--text-muted);
}
.info-box strong { color: var(--accent-blue); }

/* 章节导航按钮 */
.chapter-nav-btn {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 40px;
    padding-top: 24px;
    border-top: 1px solid var(--border);
}

/* 步骤列表 */
.step-list { counter-reset: step; list-style: none; padding-left: 0; }
.step-list li {
    counter-increment: step;
    padding: 11px 14px 11px 48px;
    position: relative;
    margin-bottom: 10px;
    background: var(--bg-elevated);
    border-radius: 6px;
    color: var(--text-muted);
    font-size: 0.92rem;
}
.step-list li::before {
    content: counter(step);
    position: absolute;
    left: 13px; top: 50%;
    transform: translateY(-50%);
    width: 24px; height: 24px;
    background: var(--accent);
    color: var(--bg-base);
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    font-weight: 700; font-size: 0.78rem;
}

.highlight { background: rgba(245,216,122,.15); color: var(--accent); padding: 2px 6px; border-radius: 3px; }

/* ========== 商品 ========== */
.products-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
}
.product-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    overflow: hidden;
}
.product-image {
    height: 160px;
    display: flex; align-items: center; justify-content: center;
    font-size: 4rem;
    background: var(--bg-elevated);
    border-bottom: 1px solid var(--border);
}
.product-info { padding: 22px; }
.product-info h3 { font-size: 1.05rem; color: var(--accent); margin-bottom: 8px; }
.product-info p  { color: var(--text-muted); font-size: 0.88rem; margin-bottom: 14px; }
.product-price { font-size: 1.25rem; font-weight: 700; color: var(--accent); margin-bottom: 14px; }
.product-features { list-style: none; margin-bottom: 18px; padding: 0; }
.product-features li { padding: 4px 0; color: var(--text-muted); font-size: 0.88rem; }
.product-features li::before { content: '✓ '; color: var(--accent-green); font-weight: bold; }

/* ========== 联系页 ========== */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 40px;
}
.contact-info h3 { font-size: 1.1rem; color: var(--accent); margin-bottom: 24px; }
.contact-item { display: flex; gap: 14px; margin-bottom: 22px; align-items: flex-start; }
.contact-icon {
    width: 42px; height: 42px;
    background: var(--bg-elevated);
    border: 1px solid var(--border);
    border-radius: 8px;
    display: flex; align-items: center; justify-content: center;
    font-size: 1.1rem; flex-shrink: 0;
}
.contact-item h4 { font-size: 0.9rem; color: var(--text-primary); margin-bottom: 4px; }
.contact-item p  { font-size: 0.88rem; color: var(--text-muted); }

.contact-form {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 32px;
}
.contact-form h3 { font-size: 1.1rem; color: var(--accent); margin-bottom: 22px; }

/* ========== 表单通用 ========== */
.form-group { margin-bottom: 18px; }
.form-group label { display: block; margin-bottom: 7px; font-size: 0.88rem; color: var(--text-muted); }
.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 10px 14px;
    background: var(--bg-elevated);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-primary);
    font-size: 0.93rem;
    font-family: inherit;
    transition: border-color .15s;
}
.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--accent);
}
.form-group textarea { resize: vertical; min-height: 110px; }
.form-group select option { background: var(--bg-card); }

/* ========== 留言板 ========== */
.guestbook-container { max-width: 860px; margin: 0 auto; }
.guestbook-form {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 30px;
    margin-bottom: 24px;
}
.guestbook-form h3 { font-size: 1.05rem; color: var(--accent); margin-bottom: 20px; }
.guestbook-list {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 30px;
}
.guestbook-list h3 { font-size: 1.05rem; color: var(--accent); margin-bottom: 20px; }
.guestbook-item {
    padding: 20px 0;
    border-bottom: 1px solid var(--border);
}
.guestbook-item:last-child { border-bottom: none; }
.guestbook-header { display: flex; align-items: center; gap: 12px; margin-bottom: 10px; }
.author-avatar {
    width: 40px; height: 40px;
    background: var(--bg-elevated);
    border: 1px solid var(--border);
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    color: var(--accent);
    font-weight: 700;
    font-size: 0.95rem;
    flex-shrink: 0;
}
.author-info h4 { font-size: 0.92rem; color: var(--text-primary); margin-bottom: 2px; }
.author-info span { font-size: 0.8rem; color: var(--text-dim); }
.guestbook-content { color: var(--text-muted); font-size: 0.92rem; line-height: 1.75; }

/* ========== 页脚 ========== */
footer {
    background: var(--bg-card);
    border-top: 1px solid var(--border);
    padding: 48px 24px 24px;
    margin-top: 60px;
}
.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 36px;
    margin-bottom: 36px;
}
.footer-section h3 { font-size: 0.85rem; text-transform: uppercase; letter-spacing: .07em; color: var(--text-dim); margin-bottom: 14px; }
.footer-section p,
.footer-section a { color: var(--text-muted); font-size: 0.88rem; line-height: 2; }
.footer-section a:hover { color: var(--accent); }
.footer-section ul { list-style: none; }
.footer-section li { margin-bottom: 4px; }
.footer-bottom {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid var(--border);
    color: var(--text-dim);
    font-size: 0.82rem;
}

/* ========== 响应式 ========== */
@media (max-width: 1024px) {
    .manual-container { grid-template-columns: 1fr; }
    .manual-sidebar { 
        position: static; 
        display: none;
    }
    .manual-sidebar.mobile-open {
        display: block;
        position: fixed;
        top: 64px;
        left: 0;
        right: 0;
        bottom: 0;
        z-index: 100;
        overflow-y: auto;
        border-radius: 0;
    }
    .contact-grid { grid-template-columns: 1fr; }
}

/* ========== 平板适配 ========== */
@media (max-width: 900px) {
    .page-container { padding: 20px 12px; }
    .page-header { padding: 28px 12px; }
    .hero { padding: 48px 12px 40px; }
    .features, .ecu-types { padding: 32px 12px; }
    .section-title { margin-bottom: 24px; }
    .section-title h2 { font-size: 1.4rem; }
    footer { padding: 28px 12px 16px; margin-top: 32px; }
    /* 手册 */
    .manual-container { padding: 16px 12px; }
}

/* ========== 手机适配 ========== */
@media (max-width: 768px) {
    /* ---- 导航 ---- */
    .nav-container { padding: 0 10px; height: 54px; }
    .logo { font-size: 1.1rem; gap: 7px; }
    .logo-icon { width: 30px; height: 30px; font-size: 0.95rem; }
    main { margin-top: 54px; }
    .nav-menu {
        position: fixed;
        left: -100%; top: 54px;
        flex-direction: column;
        background: var(--bg-card);
        border-right: 1px solid var(--border);
        width: 75%;
        max-width: 260px;
        height: calc(100vh - 54px);
        padding: 8px 0;
        transition: left .25s ease;
        gap: 0;
        box-shadow: 3px 0 16px rgba(0,0,0,0.5);
        z-index: 999;
        overflow-y: auto;
    }
    .nav-menu.active { left: 0; }
    .nav-menu li { margin: 0; }
    .nav-menu a { padding: 12px 18px; border-radius: 0; font-size: 0.97rem; }
    .menu-toggle { display: flex; }
    .nav-menu .dropdown-menu {
        position: static;
        display: block;
        background: var(--bg-elevated);
        border: none;
        box-shadow: none;
        padding-left: 16px;
        margin-top: 0;
    }
    .nav-menu .dropdown > a::after { content: ''; }

    /* ---- 全局：彻底去掉左右 max-width 限制，内容铺满屏幕 ---- */
    .page-container {
        max-width: 100%;
        padding: 14px 10px;
    }
    .page-header {
        padding: 20px 10px;
    }
    .page-header h1 { font-size: 1.35rem; margin-bottom: 6px; }
    .page-header p  { font-size: 0.9rem; }

    /* ---- Hero ---- */
    .hero { padding: 28px 10px 24px; }
    .hero-content { max-width: 100%; }
    .hero h1 { font-size: 1.5rem; line-height: 1.3; margin-bottom: 10px; }
    .hero p  { font-size: 0.93rem; margin-bottom: 18px; }
    .hero-buttons { gap: 8px; }

    /* ---- section标题 ---- */
    .section-title { margin-bottom: 16px; }
    .section-title h2 { font-size: 1.2rem; margin-bottom: 6px; }
    .section-title p  { font-size: 0.88rem; }

    /* ---- 特性/ECU卡片 ---- */
    .features { padding: 20px 10px; }
    .ecu-types { padding: 0 10px 20px; }
    .features-grid {
        max-width: 100%;
        grid-template-columns: 1fr 1fr;   /* 手机横排两列 */
        gap: 8px;
    }
    .feature-card { padding: 14px 12px; border-radius: 8px; }
    .feature-icon { font-size: 1.4rem; margin-bottom: 8px; }
    .feature-card h3 { font-size: 0.88rem; margin-bottom: 6px; }
    .feature-card p  { font-size: 0.82rem; line-height: 1.55; }
    .ecu-grid {
        max-width: 100%;
        grid-template-columns: 1fr;
        gap: 10px;
    }
    .ecu-image { height: 100px; font-size: 2.2rem; }
    .ecu-content { padding: 14px 12px; }
    .ecu-content h3 { font-size: 1rem; }
    .ecu-content p  { font-size: 0.85rem; margin-bottom: 10px; }

    /* ---- 通用卡片 ---- */
    .card { padding: 14px 10px; border-radius: 8px; }

    /* ---- 商品 ---- */
    .products-grid { grid-template-columns: 1fr; gap: 10px; }
    .product-image { height: 110px; font-size: 3rem; }
    .product-info { padding: 14px 12px; }
    .product-info h3 { font-size: 0.97rem; }
    .product-info p  { font-size: 0.85rem; }

    /* ---- 手册 ---- */
    .manual-container { padding: 10px 8px; max-width: 100%; }
    .manual-content { padding: 14px 10px; border-radius: 8px; }
    .manual-content h2 { font-size: 1.2rem; margin-bottom: 14px; padding-bottom: 10px; }
    .manual-content h3 { font-size: 0.98rem; margin: 18px 0 8px; }
    .manual-content h4 { font-size: 0.92rem; margin: 14px 0 7px; }
    .manual-content p  { font-size: 0.88rem; margin-bottom: 10px; line-height: 1.7; }
    .manual-content ul,
    .manual-content ol { font-size: 0.88rem; padding-left: 18px; margin-bottom: 10px; }
    .manual-content li { margin-bottom: 5px; }

    /* ---- 表格横向滚动 ---- */
    .manual-content table,
    .product-table,
    .param-table {
        display: block;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        font-size: 0.82rem;
        white-space: nowrap;
        max-width: 100%;
    }
    .manual-content th,
    .manual-content td,
    .product-table th,
    .product-table td,
    .param-table th,
    .param-table td { padding: 7px 9px; }

    /* ---- 提示框 ---- */
    .warning-box, .info-box { padding: 10px 12px; font-size: 0.85rem; margin: 12px 0; }

    /* ---- 步骤列表 ---- */
    .step-list li { padding: 9px 10px 9px 40px; font-size: 0.87rem; }
    .step-list li::before { left: 10px; width: 22px; height: 22px; }

    /* ---- 联系页 ---- */
    .contact-options { gap: 10px; margin-bottom: 20px; }
    .contact-option { padding: 16px 12px; border-radius: 10px; }
    .contact-option-icon { width: 44px; height: 44px; font-size: 1.5rem; margin-bottom: 10px; }
    .dealer-row {
        grid-template-columns: auto 1fr 1fr;
        font-size: 0.83rem;
    }
    .dealer-row > div { padding: 9px 8px; }
    .quick-form { padding: 16px 10px; }

    /* ---- 留言板 ---- */
    .guestbook-container { max-width: 100%; }
    .guestbook-form, .guestbook-list { padding: 16px 10px; }
    .guestbook-item { padding: 14px 0; }
    .author-avatar { width: 34px; height: 34px; font-size: 0.85rem; }
    .guestbook-content { font-size: 0.87rem; }

    /* ---- 按钮 ---- */
    .btn { padding: 9px 16px; font-size: 0.9rem; }

    /* ---- 页脚 ---- */
    footer { padding: 20px 10px 12px; margin-top: 24px; }
    .footer-content { max-width: 100%; gap: 16px; margin-bottom: 16px; grid-template-columns: 1fr 1fr; }
    .footer-section h3 { margin-bottom: 8px; }
    .footer-section p,
    .footer-section a { font-size: 0.85rem; line-height: 1.8; }
    .footer-bottom { padding-top: 12px; font-size: 0.78rem; }
}

/* ========== 小屏手机（≤480px） ========== */
@media (max-width: 480px) {
    /* 导航栏更紧凑 */
    .nav-container { height: 50px; }
    main { margin-top: 50px; }
    .nav-menu { top: 50px; height: calc(100vh - 50px); }
    .logo { font-size: 1rem; }
    .logo-icon { width: 28px; height: 28px; font-size: 0.88rem; }

    /* 全局 padding 压到最小 */
    .page-container { padding: 10px 8px; }
    .page-header { padding: 16px 8px; }
    .page-header h1 { font-size: 1.2rem; }

    /* Hero 极简 */
    .hero { padding: 22px 8px 18px; }
    .hero h1 { font-size: 1.3rem; }
    .hero p  { font-size: 0.88rem; margin-bottom: 14px; }
    .hero-buttons { gap: 6px; }
    .hero-buttons .btn { flex: 1; min-width: 0; text-align: center; justify-content: center; }
    .btn { padding: 8px 12px; font-size: 0.87rem; }

    /* 特性卡片：小屏也保持两列 */
    .features { padding: 16px 8px; }
    .ecu-types { padding: 0 8px 16px; }
    .features-grid { grid-template-columns: 1fr 1fr; gap: 6px; }
    .feature-card { padding: 12px 10px; }
    .feature-icon { font-size: 1.25rem; margin-bottom: 6px; }
    .feature-card h3 { font-size: 0.82rem; }
    .feature-card p  { font-size: 0.78rem; }

    /* section标题 */
    .section-title h2 { font-size: 1.1rem; }

    /* 卡片 */
    .card { padding: 12px 8px; }
    .manual-container { padding: 8px 6px; }
    .manual-content { padding: 12px 8px; }
    .ecu-content { padding: 12px 10px; }
    .product-info { padding: 12px 10px; }

    /* 章节导航 */
    .chapter-nav-btn { flex-direction: column; gap: 8px; margin-top: 24px; padding-top: 16px; }

    /* 表单 */
    .form-row { grid-template-columns: 1fr; gap: 0; }
    .form-group { margin-bottom: 12px; }
    .form-group input,
    .form-group textarea,
    .form-group select { padding: 9px 10px; font-size: 0.9rem; }

    /* 联系页 */
    .contact-option { padding: 14px 10px; }
    .quick-form { padding: 14px 8px; }

    /* 代理商表格：单列堆叠 */
    .dealer-row { grid-template-columns: 1fr; padding: 6px 0; }
    .dealer-row.header-row { display: none; }
    .dealer-row > div { padding: 4px 8px; font-size: 0.82rem; }

    /* 留言板 */
    .guestbook-form, .guestbook-list { padding: 12px 8px; }

    /* 页脚单列 */
    footer { padding: 16px 8px 10px; margin-top: 16px; }
    .footer-content { grid-template-columns: 1fr; gap: 12px; }
}