/* ==========================================
   全局基础样式（重置浏览器默认样式）
   ========================================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Montserrat', sans-serif;
}

body {
    color: #222; /* 全局文字主色 */
    background: #f5f7fa; /* 全局背景色 */
    overflow-x: hidden;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

/* 通用容器（居中、限制最大宽度） */
.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
}

/* ==========================================
   全局变量（快速修改整站核心样式）
   如需改色/改字体，只需修改以下变量即可
   ========================================== */
:root {
    --primary-color: #0F52BA; /* 主色：科技蓝（核心修改项） */
    --primary-hover: #0c4191; /* 主色hover效果 */
    --text-main: #222; /* 主要文字色 */
    --text-secondary: #666; /* 次要文字色 */
    --text-light: #ccc; /* 浅色文字（页脚） */
    --bg-white: #fff; /* 白色背景 */
    --bg-light: #f5f7fa; /* 浅灰背景 */
    --shadow-sm: 0 2px 10px rgba(0,0,0,0.05); /* 轻微阴影 */
    --shadow-md: 0 5px 20px rgba(0,0,0,0.05); /* 中等阴影 */
    --shadow-lg: 0 10px 30px rgba(0,0,0,0.1); /* 较大阴影 */
    --transition-base: 0.3s; /* 通用过渡动画时长 */
}

/* ==========================================
   导航栏样式
   ========================================== */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 999;
    background: rgba(255,255,255,0.95);
    box-shadow: var(--shadow-sm);
    padding: 15px 0;
    transition: padding var(--transition-base), box-shadow var(--transition-base);
}

.nav .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo img {
    height: 60px;
    object-fit: contain;
}

.nav-menu {
    display: flex;
    gap: 30px;
}

.nav-menu a {
    font-size: 16px;
    font-weight: 500;
    color: var(--text-main);
    transition: color var(--transition-base);
}

.nav-menu a:hover {
    color: var(--primary-color);
}

.nav-menu .active {
    color: var(--primary-color);
    font-weight: 600;
}

/* 汉堡菜单（手机端） */
.hamburger {
    display: none;
    font-size: 24px;
    cursor: pointer;
}

/* ==========================================
   通用按钮样式
   ========================================== */
.btn {
    display: inline-block;
    padding: 15px 30px;
    background: var(--primary-color);
    color: var(--bg-white);
    border-radius: 4px;
    font-weight: 600;
    transition: background var(--transition-base), transform var(--transition-base);
    border: none;
    cursor: pointer;
}

.btn:hover {
    background: var(--primary-hover);
    transform: translateY(-3px);
}

.btn-outline {
    background: transparent;
    border: 2px solid var(--bg-white);
    margin-left: 20px;
}

.btn-outline:hover {
    background: rgba(255,255,255,0.2);
    border-color: var(--bg-white);
}

/* ==========================================
   通用板块标题样式
   ========================================== */
.section-title {
    text-align: center;
    margin-bottom: 60px;
}

.section-title h2 {
    font-size: 36px;
    margin-bottom: 15px;
    color: var(--text-main);
}

.section-title p {
    font-size: 16px;
    color: var(--text-secondary);
    max-width: 800px;
    margin: 0 auto;
}

/* ==========================================
   首页全屏横幅样式
   ========================================== */
.banner {
    width: 100%;
    height: 100vh;
    background: url(banner_main.jpg) no-repeat center center;
    background-size: cover;
    display: flex;
    align-items: center;
    justify-content: flex-start;
    padding: 0 5%;
    margin-top: 90px;
    position: relative;
}

.banner::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.3);
    z-index: 1;
}

.banner-content {
    position: relative;
    z-index: 2;
    color: var(--bg-white);
    max-width: 600px;
}

.banner-content h1 {
    font-size: 48px;
    line-height: 1.2;
    margin-bottom: 20px;
}

.banner-content p {
    font-size: 18px;
    line-height: 1.5;
    margin-bottom: 30px;
    opacity: 0.9;
}

/* ==========================================
   首页核心优势模块样式
   ========================================== */
.advantage {
    padding: 100px 0;
    background: var(--bg-white);
}

.advantage-list {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.advantage-item {
    text-align: center;
    padding: 40px 20px;
    background: var(--bg-light);
    border-radius: 8px;
    transition: box-shadow var(--transition-base), transform var(--transition-base);
}

.advantage-item:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-5px);
}

.advantage-item img {
    height: 100px;
    margin-bottom: 20px;
}

.advantage-item h3 {
    font-size: 22px;
    margin-bottom: 15px;
    color: var(--text-main);
}

.advantage-item p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ==========================================
   首页企业简介模块样式
   ========================================== */
.about-brief {
    padding: 80px 0;
    background: var(--bg-light);
    display: flex;
    align-items: center;
    gap: 50px;
}

.about-brief .content {
    flex: 1;
}

.about-brief .content h3 {
    font-size: 30px;
    margin-bottom: 20px;
    color: var(--text-main);
}

.about-brief .content p {
    font-size: 16px;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 30px;
}

.about-brief .img-box {
    flex: 1;
    height: 400px;
    border-radius: 8px;
    overflow: hidden;
}

.about-brief .img-box img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

/* ==========================================
   首页核心业务模块样式
   ========================================== */
.business {
    padding: 100px 0;
    background: var(--bg-white);
}

.business-list {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 40px;
}

.business-item {
    padding: 30px;
    border: 1px solid #eee;
    border-radius: 8px;
    transition: box-shadow var(--transition-base);
}

.business-item:hover {
    box-shadow: var(--shadow-md);
}

.business-item h3 {
    font-size: 20px;
    margin-bottom: 15px;
    color: var(--primary-color);
}

.business-item p {
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 20px;
}

.business-item a {
    color: var(--primary-color);
    font-weight: 500;
    display: inline-flex;
    align-items: center;
    gap: 5px;
}

.business-item a:hover {
    text-decoration: underline;
}

/* ==========================================
   首页联系入口模块样式
   ========================================== */
.contact-cta {
    padding: 80px 0;
    background: var(--primary-color);
    color: var(--bg-white);
    text-align: center;
}

.contact-cta h3 {
    font-size: 32px;
    margin-bottom: 20px;
}

.contact-cta p {
    font-size: 18px;
    opacity: 0.9;
    margin-bottom: 30px;
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

.contact-cta .btn {
    background: var(--bg-white);
    color: var(--primary-color);
}

.contact-cta .btn:hover {
    background: #f0f0f0;
}

/* ==========================================
   通用页脚样式
   ========================================== */
.footer {
    padding: 50px 0 20px;
    background: #222;
    color: var(--text-light);
}

.footer .container {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 40px;
}

.footer-logo {
    flex: 1;
    min-width: 250px;
}

.footer-logo img {
    height: 50px;
    margin-bottom: 20px;
}

.footer-logo p {
    font-size: 14px;
    line-height: 1.6;
    opacity: 0.8;
}

.footer-links {
    flex: 2;
    display: flex;
    gap: 60px;
    min-width: 500px;
}

.footer-link-col h4 {
    font-size: 16px;
    color: var(--bg-white);
    margin-bottom: 20px;
    font-weight: 600;
}

.footer-link-col ul li {
    margin-bottom: 10px;
}

.footer-link-col ul li a {
    font-size: 14px;
    opacity: 0.8;
    transition: opacity var(--transition-base);
}

.footer-link-col ul li a:hover {
    opacity: 1;
    color: var(--primary-color);
}

.footer-copyright {
    text-align: center;
    padding-top: 40px;
    margin-top: 20px;
    border-top: 1px solid #333;
    font-size: 14px;
    opacity: 0.7;
}

/* ==========================================
   回到顶部按钮样式
   ========================================== */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background: var(--primary-color);
    color: var(--bg-white);
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity var(--transition-base);
    z-index: 998;
    cursor: pointer;
}

.back-to-top.show {
    opacity: 1;
}

/* ==========================================
   响应式适配（平板/手机）
   屏幕宽度 < 992px 生效
   ========================================== */
@media (max-width: 992px) {
    .nav-menu {
        display: none;
    }
    .hamburger {
        display: block;
    }
    /* 手机端展开的导航菜单 */
    .nav-menu.active {
        display: flex;
        flex-direction: column;
        position: absolute;
        top: 90px;
        left: 0;
        width: 100%;
        background: var(--bg-white);
        padding: 20px;
        box-shadow: var(--shadow-sm);
    }
    .banner-content h1 {
        font-size: 36px;
    }
    .advantage-list {
        grid-template-columns: repeat(2, 1fr);
    }
    .about-brief {
        flex-direction: column;
        gap: 30px;
    }
    .business-list {
        grid-template-columns: 1fr;
    }
}

/* ==========================================
   响应式适配（手机）
   屏幕宽度 < 768px 生效
   ========================================== */
@media (max-width: 768px) {
    .banner {
        height: 80vh;
    }
    .banner-content h1 {
        font-size: 28px;
    }
    .banner-content p {
        font-size: 16px;
    }
    .btn {
        padding: 12px 20px;
        font-size: 14px;
    }
    .btn-outline {
        margin-left: 10px;
        margin-top: 10px;
    }
    .section-title h2 {
        font-size: 28px;
    }
    .advantage-list {
        grid-template-columns: 1fr;
    }
    .footer-links {
        flex-direction: column;
        gap: 30px;
        min-width: 250px;
    }
}