/* ========== 基础变量与重置 ========== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --primary-deep: #1a365d;
    --primary: #2b6cb0;
    --primary-light: #2a4365;
    --text-dark: #2c3e50;
    --text-gray: #4a5568;
    --text-light: #718096;
    --border-light: #e2e8f0;
    --bg-page: #f4f7fa;
    --bg-white: #ffffff;
    --bg-dark-footer: #1a202c;
    --footer-text: #a0aec0;
    --shadow-sm: 0 4px 6px rgba(0,0,0,0.02);
    --shadow-card: 0 10px 25px -5px rgba(0,0,0,0.03);
    --radius: 8px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Microsoft YaHei", sans-serif;
    background: var(--bg-page);
    color: var(--text-dark);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ========== 导航栏（与首页完全一致） ========== */
header {
    background: var(--bg-white);
    box-shadow: 0 2px 12px rgba(0,0,0,0.04);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-wrapper {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    padding: 15px 0;
}

.logo-area {
    flex-shrink: 0;
}

.logo-link {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: var(--primary-deep);
    font-size: 22px;
    font-weight: 700;
    gap: 10px;
    white-space: nowrap;
}

.logo-link img {
    vertical-align: middle;
}

.menu-area {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
}

.menu-area a {
    color: var(--text-gray);
    text-decoration: none;
    font-weight: 500;
    font-size: 15px;
    padding: 5px 0;
    border-bottom: 2px solid transparent;
    transition: color 0.2s, border-color 0.2s;
}

.menu-area a:hover,
.menu-area a.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
}

/* ========== 页面Hero区 ========== */
.page-hero {
    background: linear-gradient(135deg, #1a365d 0%, #2a4365 100%);
    color: #fff;
    padding: 60px 0;
    text-align: center;
}

.page-hero h1 {
    font-size: 32px;
    font-weight: 700;
    letter-spacing: -0.5px;
    margin-bottom: 15px;
    line-height: 1.3;
}

.hero-sub {
    font-size: 18px;
    max-width: 700px;
    margin: 0 auto;
    color: #e2e8f0;
    opacity: 0.95;
}

/* ========== 主内容区 ========== */
main {
    padding: 50px 0;
}

.article-wrapper {
    background: var(--bg-white);
    padding: 35px 30px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    margin-bottom: 40px;
    border: 1px solid var(--border-light);
}

.section-title {
    font-size: 24px;
    color: var(--primary-deep);
    margin: 0 0 25px 0;
    padding-left: 12px;
    border-left: 4px solid var(--primary);
    font-weight: 700;
}

/* ========== 协议对比网格 ========== */
.protocol-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.protocol-card {
    background: #f9fbfd;
    border-radius: var(--radius);
    padding: 20px;
    border: 1px solid var(--border-light);
    transition: all 0.25s ease;
}

.protocol-card:hover {
    border-color: var(--primary);
    box-shadow: 0 8px 20px rgba(43, 108, 176, 0.06);
    transform: translateY(-2px);
}

.protocol-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 15px;
    flex-wrap: wrap;
}

.proto-icon {
    font-size: 24px;
}

.protocol-header h3 {
    font-size: 18px;
    color: var(--primary-deep);
    margin: 0;
}

.tag {
    background: #ebf8ff;
    color: var(--primary);
    font-size: 11px;
    font-weight: 600;
    padding: 2px 10px;
    border-radius: 20px;
    margin-left: auto;
}

.proto-specs {
    list-style: none;
    padding: 0;
}

.proto-specs li {
    font-size: 13px;
    color: var(--text-gray);
    padding: 6px 0;
    border-bottom: 1px dashed #edf2f7;
}

.proto-specs li:last-child {
    border-bottom: none;
}

/* ========== 参数卡片行 ========== */
.param-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-top: 20px;
}

.param-card {
    background: #f9fbfd;
    padding: 20px 18px;
    border-radius: var(--radius);
    border: 1px solid var(--border-light);
}

.param-card h3 {
    font-size: 16px;
    color: var(--primary);
    margin: 0 0 10px 0;
}

.param-card p {
    font-size: 13px;
    color: var(--text-gray);
    margin: 0;
    line-height: 1.6;
}

.param-card code {
    background: #edf2f7;
    padding: 2px 6px;
    border-radius: 3px;
    font-family: "Cascadia Code", monospace;
    color: #2b6cb0;
}

/* ========== 提示框 ========== */
.alert-box {
    background: #f0f9ff;
    border-left: 4px solid var(--primary);
    color: var(--primary);
    padding: 15px 20px;
    border-radius: 4px;
    margin: 25px 0 0;
    font-size: 14px;
}

/* ========== 视频容器 ========== */
.video-container {
    max-width: 750px;
    margin: 0 auto;
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: 0 15px 30px rgba(0,0,0,0.05);
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    background: #000;
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

/* ========== FAQ 折叠面板 ========== */
.faq-list {
    display: flex;
    flex-direction: column;
    gap: 15px;
    margin-top: 20px;
}

.faq-item {
    background: #f9fbfd;
    border-radius: var(--radius);
    border: 1px solid var(--border-light);
    overflow: hidden;
}

.faq-item summary {
    padding: 18px 20px;
    font-weight: 600;
    color: var(--primary-deep);
    cursor: pointer;
    outline: none;
    transition: background 0.2s;
    list-style: none;
}

.faq-item summary::-webkit-details-marker {
    display: none;
}

.faq-item summary:hover {
    background: #f0f5fa;
}

.faq-item[open] summary {
    border-bottom: 1px solid var(--border-light);
    background: #f0f5fa;
    color: var(--primary);
}

.faq-content {
    padding: 0 20px 18px;
    font-size: 14px;
    color: var(--text-gray);
    line-height: 1.8;
}

.faq-content p {
    margin: 0;
}

/* ========== CTA 区域 ========== */
.cta-section {
    text-align: center;
    padding: 25px;
    background: var(--bg-white);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px dashed var(--primary);
    color: var(--text-gray);
    font-size: 16px;
}

.cta-section a {
    color: var(--primary);
    font-weight: 600;
    text-decoration: none;
    border-bottom: 1px solid var(--primary);
    transition: opacity 0.2s;
}

.cta-section a:hover {
    opacity: 0.8;
}

/* ========== 页脚（与首页完全一致） ========== */
footer {
    background: var(--bg-dark-footer);
    color: var(--footer-text);
    padding: 50px 0 0;
    border-top: 4px solid var(--primary);
    font-size: 14px;
}

.footer-table {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    gap: 30px;
    padding-bottom: 30px;
}

.footer-row {
    display: flex;
    flex-wrap: wrap;
    width: 100%;
    gap: 30px;
}

.footer-cell {
    flex: 1 1 200px;
    min-width: 160px;
}

.footer-cell h4 {
    color: #fff;
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 20px;
    letter-spacing: 0.3px;
}

.footer-cell ul {
    list-style: none;
}

.footer-cell ul li {
    margin-bottom: 12px;
}

.footer-cell ul li a {
    color: var(--footer-text);
    text-decoration: none;
    transition: color 0.2s;
}

.footer-cell ul li a:hover {
    color: #fff;
}

.footer-bottom {
    border-top: 1px solid #2d3748;
    padding: 20px 0;
    text-align: center;
    font-size: 13px;
    color: var(--footer-text);
    line-height: 1.8;
}

/* ========== 响应式设计 ========== */
@media (max-width: 768px) {
    .nav-wrapper {
        flex-direction: column;
        gap: 15px;
        text-align: center;
    }
    .menu-area {
        justify-content: center;
    }
    .page-hero h1 {
        font-size: 26px;
    }
    .hero-sub {
        font-size: 16px;
    }
    .article-wrapper {
        padding: 20px;
    }
    .protocol-grid,
    .param-row {
        grid-template-columns: 1fr;
    }
    .footer-row {
        flex-direction: column;
    }
}