/* 全局变量 - 自然科技风格 */
:root {
    --primary-color: #2ecc71; /* 生机绿 */
    --secondary-color: #27ae60; /* 深绿 */
    --accent-color: #3498db; /* 科技蓝 */
    --bg-color: #f4f9f4; /* 极淡绿背景 */
    --surface-color: #ffffff;
    --text-main: #2c3e50;
    --text-light: #7f8c8d;
    --border-radius: 8px;
    --shadow: 0 4px 12px rgba(46, 204, 113, 0.1);
    --font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
}

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

body {
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
}

a {
    text-decoration: none;
    color: inherit;
    transition: all 0.3s ease;
}

ul {
    list-style: none;
}

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

/* 顶部导航 */
.bio-header {
    background: var(--surface-color);
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
    position: sticky;
    top: 0;
    z-index: 1000;
    border-bottom: 3px solid var(--primary-color);
}

.header-flex {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 1.4rem;
    font-weight: bold;
    color: var(--secondary-color);
}

.nav-links a {
    margin: 0 15px;
    font-weight: 500;
    color: var(--text-main);
    text-transform: uppercase;
    font-size: 0.9rem;
}

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

.btn-search {
    background: var(--bg-color);
    color: var(--text-main);
    padding: 8px 15px;
    border-radius: 20px;
    font-size: 0.9rem;
    border: 1px solid #ddd;
}

.btn-search:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

/* 英雄区域 */
.hero-banner {
    padding: 80px 0;
    background: linear-gradient(135deg, #f4f9f4 0%, #e8f5e9 100%);
}

.hero-content {
    display: flex;
    align-items: center;
    gap: 50px;
}

.hero-text {
    flex: 1;
}

.tag-science {
    display: inline-block;
    background: var(--accent-color);
    color: var(--white);
    padding: 4px 12px;
    border-radius: var(--border-radius);
    font-size: 0.8rem;
    margin-bottom: 15px;
    font-weight: bold;
}

.hero-text h1 {
    font-size: 3.2rem;
    margin-bottom: 10px;
    line-height: 1.2;
    color: var(--secondary-color);
}

.subtitle {
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 20px;
}

.feature-list li {
    margin-bottom: 10px;
    font-size: 1.1rem;
    color: var(--text-main);
}

.hero-btns {
    margin-top: 30px;
    display: flex;
    gap: 15px;
}

.btn-explore {
    padding: 12px 30px;
    background: var(--primary-color);
    color: var(--white);
    border-radius: var(--border-radius);
    font-weight: bold;
    box-shadow: 0 4px 10px rgba(46, 204, 113, 0.3);
}

.btn-explore:hover {
    background: var(--secondary-color);
    transform: translateY(-2px);
}

.btn-subscribe {
    padding: 12px 30px;
    background: transparent;
    color: var(--secondary-color);
    border: 2px solid var(--secondary-color);
    border-radius: var(--border-radius);
    font-weight: bold;
}

.btn-subscribe:hover {
    background: var(--secondary-color);
    color: var(--white);
}

.hero-img-box {
    flex: 1;
}

.hero-img-box img {
    width: 100%;
    border-radius: var(--border-radius);
    box-shadow: 0 10px 30px rgba(0,0,0,0.1);
    border: 5px solid var(--white);
}

/* 通用区块 */
.section-area {
    padding: 80px 0;
}

.bg-light {
    background: #ffffff;
}

.bg-dark {
    background: var(--secondary-color);
    color: var(--white);
}

.section-head {
    text-align: center;
    margin-bottom: 50px;
}

.section-head h2 {
    font-size: 2.2rem;
    margin-bottom: 10px;
    color: var(--secondary-color);
}

.section-head.light h2 {
    color: var(--white);
}

.section-head p {
    color: var(--text-light);
}

.section-head.light p {
    color: #e8f5e9;
}

/* 研究领域卡片 */
.field-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 30px;
}

.field-card {
    background: var(--surface-color);
    padding: 30px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    text-align: center;
    transition: transform 0.3s;
    border-top: 4px solid var(--primary-color);
}

.field-card:hover {
    transform: translateY(-5px);
}

.icon-box {
    font-size: 3rem;
    margin-bottom: 20px;
}

.field-card h3 {
    margin-bottom: 10px;
    color: var(--text-main);
}

.field-card p {
    color: var(--text-light);
    font-size: 0.95rem;
    margin-bottom: 20px;
}

.link-more {
    color: var(--primary-color);
    font-weight: bold;
    font-size: 0.9rem;
}

.link-more:hover {
    color: var(--secondary-color);
}

/* 新闻布局 */
.news-layout {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 30px;
}

.news-main {
    background: var(--surface-color);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow);
}

.news-main img {
    width: 100%;
    height: 300px;
    object-fit: cover;
}

.news-info {
    padding: 25px;
}

.category {
    display: inline-block;
    background: var(--accent-color);
    color: var(--white);
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 0.8rem;
    margin-bottom: 10px;
}

.news-info h3 {
    font-size: 1.5rem;
    margin-bottom: 10px;
    color: var(--text-main);
}

.news-info p {
    color: var(--text-light);
    margin-bottom: 20px;
}

.btn-read {
    display: inline-block;
    padding: 8px 20px;
    background: var(--bg-color);
    color: var(--secondary-color);
    border-radius: var(--border-radius);
    font-weight: bold;
}

.btn-read:hover {
    background: var(--secondary-color);
    color: var(--white);
}

.news-side {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.side-item {
    display: flex;
    gap: 15px;
    background: var(--surface-color);
    padding: 15px;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    align-items: center;
}

.side-item img {
    width: 80px;
    height: 80px;
    object-fit: cover;
    border-radius: 6px;
}

.side-text h4 {
    font-size: 1rem;
    margin-bottom: 5px;
    color: var(--text-main);
}

.side-text .date {
    font-size: 0.8rem;
    color: var(--text-light);
}

/* 资源区域 */
.resource-tabs {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-bottom: 40px;
}

.tab-item {
    padding: 10px 25px;
    background: rgba(255,255,255,0.2);
    border-radius: 30px;
    cursor: pointer;
    transition: background 0.3s;
}

.tab-item.active {
    background: var(--white);
    color: var(--secondary-color);
    font-weight: bold;
}

.resource-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 25px;
}

.resource-card {
    background: rgba(255,255,255,0.1);
    border-radius: var(--border-radius);
    overflow: hidden;
    transition: transform 0.3s;
    position: relative;
    border: 1px solid rgba(255,255,255,0.2);
}

.resource-card:hover {
    transform: translateY(-5px);
    background: rgba(255,255,255,0.15);
}

.res-badge {
    position: absolute;
    top: 10px;
    right: 10px;
    background: #e74c3c;
    color: var(--white);
    padding: 2px 8px;
    border-radius: 4px;
    font-size: 0.7rem;
    font-weight: bold;
}

.resource-card img {
    width: 100%;
    height: 150px;
    object-fit: cover;
}

.resource-card h4 {
    padding: 15px 15px 5px;
    font-size: 1.1rem;
}

.resource-card p {
    padding: 0 15px 15px;
    font-size: 0.9rem;
    opacity: 0.8;
}

/* 页脚 */
.site-footer {
    background: #1e8449;
    color: #e8f5e9;
    padding: 60px 0 20px;
}

.footer-layout {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 40px;
    margin-bottom: 40px;
}

.footer-col h4 {
    color: var(--white);
    margin-bottom: 20px;
}

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

.footer-col ul li a:hover {
    color: var(--white);
    text-decoration: underline;
}

.copyright {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid #27ae60;
    font-size: 0.85rem;
}

/* 响应式适配 */
@media (max-width: 768px) {
    .header-flex {
        flex-direction: column;
        height: auto;
        padding: 15px 0;
        gap: 15px;
    }

    .nav-links {
        display: flex;
        flex-wrap: wrap;
        justify-content: center;
        gap: 10px;
    }

    .hero-content {
        flex-direction: column-reverse;
        text-align: center;
    }

    .hero-btns {
        justify-content: center;
    }

    .news-layout {
        grid-template-columns: 1fr;
    }

    .footer-layout {
        grid-template-columns: 1fr;
        text-align: center;
    }
}