/* 全局样式 */
:root {
    --primary-color: #2c3e50;
    --secondary-color: #3498db;
    --accent-color: #e74c3c;
    --text-color: #333;
    --light-bg: #f5f6fa;
    --white: #ffffff;
}

html {
    scroll-behavior: smooth;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
}

/* 导航栏样式 */
.navbar {
    background-color: var(--white);
    padding: 1rem 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

.logo h1 {
    color: var(--primary-color);
    font-size: 1.8rem;
}

.nav-links {
    display: flex;
    list-style: none;
}

.nav-links li {
    margin-left: 2rem;
}

.nav-links a {
    text-decoration: none;
    color: var(--primary-color);
    font-weight: 500;
    transition: color 0.3s ease;
}

.nav-links a:hover {
    color: var(--secondary-color);
}

/* 英雄区域样式 */
#hero {
    height: 100vh;
    background: linear-gradient(rgba(44, 62, 80, 0.8), rgba(44, 62, 80, 0.8)),
                url('https://images.unsplash.com/photo-1523050854058-8df90110c9f1?ixlib=rb-1.2.1&auto=format&fit=crop&w=1950&q=80');
    background-size: cover;
    background-position: center;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: var(--white);
    padding: 0 1rem;
}

.hero-content h1 {
    font-size: 3.5rem;
    margin-bottom: 1rem;
}

.hero-content p {
    font-size: 1.5rem;
    margin-bottom: 2rem;
}

/* 按钮样式增强 */
.cta-button {
    display: inline-block;
    padding: 1rem 2rem;
    background-color: var(--secondary-color);
    color: var(--white);
    text-decoration: none;
    border-radius: 5px;
    transition: all 0.3s ease;
    font-weight: bold;
    text-transform: uppercase;
    letter-spacing: 1px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.cta-button:hover {
    background-color: #2980b9;
    transform: translateY(-2px);
    box-shadow: 0 6px 8px rgba(0, 0, 0, 0.2);
}

.cta-button:active {
    transform: translateY(0);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

/* 章节通用样式 */
.section {
    padding: 5rem 10%;
}

.section h2 {
    text-align: center;
    color: var(--primary-color);
    margin-bottom: 3rem;
    font-size: 2.5rem;
}

/* 关于我们部分 */
.about-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
    align-items: center;
}

.about-text p {
    font-size: 1.1rem;
    line-height: 1.8;
}

.stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
    text-align: center;
}

.stat-item h3 {
    font-size: 2.5rem;
    color: var(--secondary-color);
    margin-bottom: 0.5rem;
}

/* 学术项目部分 */
.programs-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.program-card {
    background-color: var(--white);
    padding: 2rem;
    border-radius: 10px;
    text-align: center;
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
    transition: transform 0.3s ease;
}

.program-card:hover {
    transform: translateY(-10px);
}

.program-card i {
    font-size: 3rem;
    color: var(--secondary-color);
    margin-bottom: 1rem;
}

/* 研究领域部分 */
.research-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.research-item {
    background-color: var(--light-bg);
    padding: 2rem;
    border-radius: 10px;
    text-align: center;
}

/* 联系我们部分 */
.contact-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
}

.contact-info {
    background-color: var(--light-bg);
    padding: 2rem;
    border-radius: 10px;
}

.contact-info p {
    margin: 1rem 0;
}

.contact-info i {
    color: var(--secondary-color);
    margin-right: 0.5rem;
}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.contact-form input,
.contact-form textarea {
    padding: 1rem;
    border: 1px solid #ddd;
    border-radius: 5px;
    font-size: 1rem;
}

.contact-form textarea {
    height: 150px;
    resize: vertical;
}

.submit-button {
    background-color: var(--secondary-color);
    color: var(--white);
    padding: 1rem;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

.submit-button:hover {
    background-color: #2980b9;
}

/* 页脚样式 */
footer {
    background-color: var(--primary-color);
    color: var(--white);
    padding: 3rem 10% 1rem;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3 {
    margin-bottom: 1rem;
}

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

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: var(--white);
    text-decoration: none;
}

.social-links {
    display: flex;
    gap: 1rem;
}

.social-links a {
    color: var(--white);
    font-size: 1.5rem;
    transition: color 0.3s ease;
}

.social-links a:hover {
    color: var(--secondary-color);
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    border-top: 1px solid rgba(255,255,255,0.1);
}

/* 响应式设计 */
@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
        padding: 1rem;
    }

    .nav-links {
        margin-top: 1rem;
        flex-direction: column;
        text-align: center;
    }

    .nav-links li {
        margin: 0.5rem 0;
    }

    .hero-content h1 {
        font-size: 2.5rem;
    }

    .about-content,
    .contact-content {
        grid-template-columns: 1fr;
    }

    .section {
        padding: 3rem 5%;
    }
}