/* ============================================
   CAAC.AI 中国民航人工智能创新中心
   全站共享样式表
   配色：红色（民航/中国）+ 黄色（创新/活力）
   ============================================ */

/* ---- 设计令牌 ---- */
:root {
    /* 红色系 - 主色调 */
    --red-primary: #C62828;
    --red-dark: #B71C1C;
    --red-deep: #8E0000;
    --red-light: #EF5350;
    --red-bg: #FFEBEE;

    /* 黄色系 - 辅色调 */
    --yellow-primary: #FFC107;
    --yellow-dark: #FF8F00;
    --yellow-light: #FFE082;
    --yellow-bg: #FFF8E1;

    /* 中性色 */
    --text-primary: #1a1a1a;
    --text-secondary: #555;
    --text-light: #888;
    --bg-white: #ffffff;
    --bg-gray: #f8f9fa;
    --bg-gray-2: #f0f1f3;
    --bg-dark: #1a1a1a;
    --bg-dark-2: #2a2a2a;
    --border-color: #e0e0e0;

    /* 渐变 */
    --gradient-main: linear-gradient(135deg, #C62828 0%, #FF8F00 100%);
    --gradient-hero: linear-gradient(135deg, #8E0000 0%, #C62828 40%, #FF8F00 100%);
    --gradient-yellow: linear-gradient(135deg, #FFC107 0%, #FF8F00 100%);
    --gradient-red: linear-gradient(135deg, #C62828 0%, #8E0000 100%);

    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 20px rgba(198,40,40,0.12);
    --shadow-lg: 0 8px 40px rgba(198,40,40,0.18);
    --shadow-card: 0 2px 12px rgba(0,0,0,0.08);

    /* 尺寸 */
    --header-height: 70px;
    --max-width: 1400px;
    --radius-sm: 8px;
    --radius-md: 14px;
    --radius-lg: 20px;
}

/* ---- 基础重置 ---- */
* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    font-family: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
    color: var(--text-primary);
    background: var(--bg-white);
    line-height: 1.6;
    overflow-x: hidden;
    padding-top: var(--header-height);
}

a { text-decoration: none; color: inherit; }
ul { list-style: none; }
img { max-width: 100%; display: block; }

/* ============================================
   顶部导航栏（全站共享）
   ============================================ */
.header {
    position: fixed;
    top: 0; left: 0; right: 0;
    height: var(--header-height);
    background: rgba(255,255,255,0.95);
    backdrop-filter: blur(12px);
    box-shadow: var(--shadow-sm);
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 48px;
    border-bottom: 3px solid;
    border-image: var(--gradient-main) 1;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    width: 44px; height: 44px;
    background: var(--gradient-main);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 18px;
    font-weight: bold;
    box-shadow: var(--shadow-md);
    letter-spacing: -1px;
}

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

.logo-text span { color: var(--yellow-dark); }

.nav {
    display: flex;
    gap: 28px;
    align-items: center;
}

.nav a {
    color: var(--text-primary);
    font-size: 15px;
    font-weight: 500;
    padding: 8px 4px;
    position: relative;
    transition: color 0.3s;
}

.nav a:hover, .nav a.active { color: var(--red-primary); }

.nav a::after {
    content: '';
    position: absolute;
    bottom: 0; left: 0;
    width: 0; height: 3px;
    background: var(--gradient-main);
    border-radius: 2px;
    transition: width 0.3s;
}

.nav a:hover::after, .nav a.active::after { width: 100%; }

.nav-cta {
    background: var(--gradient-main);
    color: #fff !important;
    padding: 8px 20px !important;
    border-radius: 8px;
    font-size: 14px;
}

.nav-cta::after { display: none; }

.nav-cta:hover { opacity: 0.9; }

/* 移动端菜单按钮 */
.nav-toggle {
    display: none;
    font-size: 24px;
    background: none;
    border: none;
    cursor: pointer;
    color: var(--red-primary);
}

/* ============================================
   通用布局
   ============================================ */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 48px;
}

.section {
    padding: 54px 0;
}

.section-gray { background: #fff; }
.section-dark { background: var(--bg-dark); color: #fff; }
.section-yellow-bg { background: #fff; }

.section-tag {
    display: inline-block;
    background: var(--red-bg);
    color: var(--red-primary);
    padding: 4px 16px;
    border-radius: 20px;
    font-size: 13px;
    font-weight: 600;
    margin-bottom: 8px;
}

.section-tag.yellow {
    background: var(--yellow-bg);
    color: var(--yellow-dark);
}

.section-tag.dark {
    background: rgba(255,193,7,0.15);
    color: var(--yellow-primary);
}

.section-title {
    font-size: 32px;
    font-weight: 800;
    color: var(--text-primary);
    margin-bottom: 10px;
    line-height: 1.3;
}

.section-title .accent {
    background: var(--gradient-main);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-title.white { color: #fff; }
.section-title.white .accent {
    background: var(--gradient-yellow);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-desc {
    font-size: 16px;
    color: var(--text-secondary);
    max-width: 700px;
    margin-bottom: 30px;
}

.section-dark .section-desc { color: rgba(255,255,255,0.7); }

/* ============================================
   按钮
   ============================================ */
.btn {
    padding: 11px 28px;
    border-radius: 10px;
    font-size: 15px;
    font-weight: 600;
    transition: all 0.3s;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    border: none;
}

.btn-primary {
    background: var(--yellow-primary);
    color: var(--red-deep);
    box-shadow: 0 4px 20px rgba(255,193,7,0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 28px rgba(255,193,7,0.55);
}

.btn-red {
    background: var(--gradient-main);
    color: #fff;
    box-shadow: 0 4px 20px rgba(198,40,40,0.3);
}

.btn-red:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 28px rgba(198,40,40,0.4);
}

.btn-outline {
    background: transparent;
    color: var(--red-primary);
    border: 2px solid var(--red-primary);
}

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

.btn-outline-white {
    background: transparent;
    color: #fff;
    border: 2px solid rgba(255,255,255,0.5);
}

.btn-outline-white:hover {
    background: rgba(255,255,255,0.1);
    border-color: #fff;
}

/* ============================================
   页面横幅（子页面顶部）
   ============================================ */
.page-banner {
    background: var(--gradient-hero);
    padding: 40px 0 34px;
    text-align: center;
    color: #fff;
    position: relative;
    overflow: hidden;
}

.page-banner::before {
    content: '';
    position: absolute;
    top: -50%; right: -20%;
    width: 600px; height: 600px;
    background: radial-gradient(circle, rgba(255,193,7,0.12) 0%, transparent 70%);
    border-radius: 50%;
}

.page-banner-content {
    position: relative;
    z-index: 2;
}

.page-banner h1 {
    font-size: 34px;
    font-weight: 800;
    margin-bottom: 8px;
    letter-spacing: 1px;
}

.page-banner p {
    font-size: 17px;
    opacity: 0.85;
    max-width: 700px;
    margin: 0 auto;
}

/* 面包屑导航 */
.breadcrumb {
    background: #fff;
    padding: 10px 0;
    font-size: 14px;
    color: var(--text-light);
    border-bottom: 1px solid var(--border-color);
}

.breadcrumb a { color: var(--red-primary); }
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb span { margin: 0 8px; }

/* ============================================
   卡片网格
   ============================================ */
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }

/* 通用卡片 */
.card {
    background: #fff;
    border-radius: var(--radius-md);
    padding: 24px;
    box-shadow: var(--shadow-card);
    transition: all 0.3s;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.card-border-top { border-top: 4px solid var(--red-primary); }
.card-border-top.yellow { border-top-color: var(--yellow-dark); }

/* 图标圆 */
.icon-circle {
    width: 48px; height: 48px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
    margin-bottom: 12px;
}

.icon-circle.red { background: var(--gradient-main); color: #fff; }
.icon-circle.yellow { background: var(--gradient-yellow); color: #fff; }
.icon-circle.light-red { background: var(--red-bg); color: var(--red-primary); }
.icon-circle.light-yellow { background: var(--yellow-bg); color: var(--yellow-dark); }

/* ============================================
   数据统计块
   ============================================ */
.stat-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 9px 0;
    border-bottom: 1px solid var(--border-color);
}

.stat-row:last-child { border-bottom: none; }

.stat-label { font-size: 14px; color: var(--text-secondary); }

.stat-value {
    font-size: 22px;
    font-weight: 800;
    color: var(--red-primary);
}

.stat-value span {
    font-size: 13px;
    font-weight: 400;
    color: var(--text-light);
}

/* 大数字展示 */
.big-stat {
    text-align: center;
}

.big-stat-num {
    font-size: 36px;
    font-weight: 900;
    background: var(--gradient-main);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
}

.big-stat-label {
    font-size: 14px;
    color: var(--text-secondary);
    margin-top: 6px;
}

/* ============================================
   时间线
   ============================================ */
.timeline {
    position: relative;
    padding-left: 40px;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 12px; top: 0; bottom: 0;
    width: 3px;
    background: var(--gradient-main);
    border-radius: 2px;
}

.timeline-item {
    position: relative;
    margin-bottom: 22px;
    padding-left: 28px;
}

.timeline-item::before {
    content: '';
    position: absolute;
    left: -34px; top: 6px;
    width: 14px; height: 14px;
    background: var(--yellow-primary);
    border: 3px solid var(--red-primary);
    border-radius: 50%;
    z-index: 1;
}

.timeline-date {
    display: inline-block;
    background: var(--gradient-main);
    color: #fff;
    padding: 2px 14px;
    border-radius: 12px;
    font-size: 13px;
    font-weight: 600;
    margin-bottom: 8px;
}

.timeline-item h4 {
    font-size: 17px;
    margin-bottom: 6px;
}

.timeline-item p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.7;
}

/* ============================================
   标签
   ============================================ */
.tag {
    display: inline-block;
    background: var(--bg-gray);
    color: var(--text-secondary);
    padding: 3px 10px;
    border-radius: 6px;
    font-size: 12px;
}

.tag.red { background: var(--red-bg); color: var(--red-primary); }
.tag.yellow { background: var(--yellow-bg); color: var(--yellow-dark); }

.tag-group {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin-top: 12px;
}

/* ============================================
   表格
   ============================================ */
.data-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 14px;
}

.data-table th {
    background: var(--gradient-main);
    color: #fff;
    padding: 14px 16px;
    text-align: left;
    font-weight: 600;
}

.data-table th:first-child { border-radius: 10px 0 0 0; }
.data-table th:last-child { border-radius: 0 10px 0 0; }

.data-table td {
    padding: 14px 16px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
}

.data-table tr:hover td { background: var(--bg-gray); }

/* ============================================
   表单
   ============================================ */
.form-group {
    margin-bottom: 14px;
}

.form-label {
    display: block;
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.form-label .required { color: var(--red-primary); }

.form-input, .form-textarea, .form-select {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    font-size: 15px;
    font-family: inherit;
    transition: border-color 0.3s;
    background: #fff;
}

.form-input:focus, .form-textarea:focus, .form-select:focus {
    outline: none;
    border-color: var(--red-primary);
}

.form-textarea {
    resize: vertical;
    min-height: 140px;
}

/* ============================================
   Footer（全站共享）
   ============================================ */
.footer {
    background: #fff;
    color: var(--text-secondary);
    padding: 40px 0 24px;
    border-top: 2px solid rgba(198,40,40,0.1);
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 28px;
    margin-bottom: 28px;
}

.footer-brand h3 {
    color: var(--red-primary);
    font-size: 17px;
    margin-bottom: 12px;
}

.footer-brand p {
    font-size: 12px;
    line-height: 1.8;
    color: var(--text-secondary);
}

.footer-col h4 {
    color: var(--red-primary);
    font-size: 13px;
    margin-bottom: 16px;
}

.footer-col ul li {
    margin-bottom: 6px;
    color: var(--text-secondary);
}

.footer-col ul li a {
    color: var(--text-secondary);
    font-size: 12px;
    transition: color 0.3s;
}

.footer-col ul li a:hover { color: var(--red-primary); }

.footer-bottom {
    padding-top: 20px;
    border-top: 1px solid rgba(198,40,40,0.12);
    text-align: center;
    font-size: 11px;
    color: var(--text-light);
}

.footer-bottom a { color: var(--text-light); }

/* ============================================
   工具类
   ============================================ */
.text-center { text-align: center; }
.text-red { color: var(--red-primary); }
.text-yellow { color: var(--yellow-dark); }
.mt-20 { margin-top: 20px; }
.mt-40 { margin-top: 28px; }
.mt-60 { margin-top: 40px; }
.mb-20 { margin-bottom: 20px; }
.mb-40 { margin-bottom: 28px; }

/* 渐入动画 */
.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ============================================
   响应式
   ============================================ */
@media (max-width: 1024px) {
    .nav { display: none; }
    .nav-toggle { display: block; }
    .nav.open {
        display: flex;
        position: absolute;
        top: var(--header-height);
        left: 0; right: 0;
        flex-direction: column;
        background: #fff;
        padding: 20px;
        gap: 16px;
        box-shadow: var(--shadow-md);
    }
    .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr 1fr; }
    .container { padding: 0 24px; }
    .section { padding: 40px 0; }
    .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 640px) {
    .grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; }
    .footer-bottom { flex-direction: column; gap: 12px; }
    .section-title { font-size: 26px; }
    .page-banner h1 { font-size: 28px; }
    .header { padding: 0 20px; }
    .container { padding: 0 20px; }
}