/* 主页样式 */
main {
    margin-top: -60px; /* 抵消header的padding */
}

.hero {
    height: 100vh;
    width: 100%;
    background-image: url('../images/index_big.png');
    background-size: cover;
    background-position: center center;
    background-repeat: no-repeat;
    position: relative;
    display: flex;
    align-items: center;
    margin-top: -60px;
    overflow: hidden;
}

.hero-content {
    position: relative;
    width: 100%;
    z-index: 2;
    display: flex;
    align-items: flex-end;
    height: 100%;
    padding-bottom: 120px;
}

.hero h1 {
    font-size: 3.8em;
    font-weight: 300;
    line-height: 1.2;
    white-space: nowrap;
    margin: 0 0 0 80px;
    color: #fff;
    text-shadow: 2px 2px 20px rgba(0, 0, 0, 0.4);
    letter-spacing: 1px;
    opacity: 0.95;
    transform: translateY(20px);
    animation: fadeInUp 1s ease-out forwards;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(40px);
    }
    to {
        opacity: 0.95;
        transform: translateY(20px);
    }
}

.section-header {
    margin-bottom: 2.5rem;
    text-align: center;
}

.section-header h2 {
    font-size: 2.5em;
    font-weight: 500;
    color: #2c3e50;
    margin: 0;
    position: relative;
    display: inline-block;
}

.section-header h2::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background: #3498db;
    border-radius: 2px;
}

/* 研究动机部分 */
.motivation {
    padding: 60px 0;
    background: #fff;
}

.lead-text {
    font-size: 1.5em;
    line-height: 1.6;
    color: #34495e;
    margin-bottom: 3rem;
    max-width: 100%;
}

.image-feature {
    margin: 0 0 3rem;
}

.image-feature img {
    width: 100%;
    height: auto;
    border-radius: 8px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.1);
}

/* 研究重点部分 */
.research-focus {
    padding: 60px 0;
    background: #f0f4f8;
}

.focus-grid {
    display: grid;
    grid-template-columns: repeat(4, 300px);
    gap: 2.5rem;
    justify-content: center;
    max-width: 1400px;
    margin: 0 auto;
}

.focus-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-decoration: none;
    color: inherit;
    transition: transform 0.3s ease;
    width: 300px;
}

.focus-item:hover {
    transform: translateY(-10px);
}

.focus-item img {
    width: 300px;
    height: 225px;
    object-fit: cover;
    border-radius: 4px;
    margin-bottom: 1rem;
    transition: transform 0.3s ease;
}

.focus-item h3 {
    font-size: 1.2em;
    font-weight: 500;
    color: #333;
    margin: 0;
}

/* 使命部分 */
.mission {
    padding: 60px 0;
    background: linear-gradient(to bottom, #fff, #f8f9fa);
    text-align: center;
}

.mission-content {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 20px;
}

.mission-content .lead-text {
    font-size: 1.5em;
    line-height: 1.6;
    color: #34495e;
    margin-bottom: 2.5rem;
}

.cta-button {
    display: inline-block;
    padding: 1rem 2rem;
    background: #0066cc;
    color: white;
    text-decoration: none;
    border-radius: 4px;
    font-weight: 500;
    transition: background 0.3s ease;
    margin-top: 2rem;
}

.cta-button:hover {
    background: #004999;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .hero {
        height: 60vh;
        background-position: center top;
    }

    .hero h1 {
        font-size: calc(2rem + 2vw);
        margin: 0 20px;
        white-space: normal;
    }

    .hero-content {
        padding-bottom: 60px;
        align-items: flex-end;
    }

    .text-columns {
        column-count: 1;
    }

    .focus-grid {
        grid-template-columns: 1fr;
    }

    .section-header h2 {
        font-size: 2em;
    }

    .lead-text {
        font-size: 1.2em;
        line-height: 1.5;
    }

    .focus-item img {
        width: 100%;
        max-width: 400px;
        height: 300px;
    }

    .motivation,
    .research-focus,
    .mission {
        padding: 40px 0;
    }

    .section-header {
        margin-bottom: 2rem;
    }

    .section-header h2 {
        font-size: 2em;
    }

    .lead-text {
        font-size: 1.2em;
        margin-bottom: 2rem;
    }

    .mission-content {
        padding: 0 15px;
    }

    .mission-content .lead-text {
        font-size: 1.2em;
        line-height: 1.5;
    }
} 

.hero-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0);
} 

/* 添加平板尺寸的响应式样式 */
@media (min-width: 769px) and (max-width: 1024px) {
    .hero {
        height: 80vh;
    }

    .hero h1 {
        font-size: calc(2rem + 1.5vw);
        max-width: 80%;
    }
}

/* 添加横屏模式的响应式样式 */
@media (max-width: 768px) and (orientation: landscape) {
    .hero {
        height: 100vh;
    }

    .hero h1 {
        font-size: calc(1.2rem + 1.5vw);
    }

    .hero-content {
        padding-bottom: 40px;
    }
} 

.text-columns,
.caption {
    display: none;
} 

/* 响应式调整 */
@media (max-width: 1300px) {
    .focus-grid {
        grid-template-columns: repeat(2, 300px);
        gap: 2rem;
    }
}

@media (max-width: 768px) {
    .focus-grid {
        grid-template-columns: 300px;
        gap: 2rem;
    }

    .focus-item,
    .focus-item img {
        width: 300px;
    }
} 

.image-caption {
    text-align: center;
    color: #666;
    font-size: 1rem;
    margin-top: 1rem;
    font-style: italic;
} 

/* 修改研究动机部分的样式 */
.motivation-text p {
    text-indent: 2em;  /* 添加首行缩进 */
    margin-bottom: 15px;  /* 减小段落间距 */
}

.motivation-section {
    padding: 60px 0;  /* 减小上下内边距 */
}

/* 如果底部还是有太多空白，可以调整以下属性 */
.footer {
    margin-top: 0;  /* 移除顶部边距 */
}

/* 如果使用了 section 标签，也可以调整它的边距 */
section:last-of-type {
    margin-bottom: 0;  /* 移除最后一个 section 的底部边距 */
    padding-bottom: 40px;  /* 减小底部内边距 */
} 

/* 研究动机部分样式 */
.motivation {
    padding: 60px 0;  /* 减小上下内边距 */
}

.motivation p {
    text-indent: 2em;  /* 添加首行缩进 */
    margin-bottom: 15px;  /* 减小段落间距 */
    line-height: 1.8;
}

/* 调整所有 section 的间距 */
.section {
    padding: 60px 0;  /* 统一所有 section 的内边距 */
}

/* 调整最后一个 section */
.section:last-child {
    padding-bottom: 40px;  /* 减小最后一个 section 的底部内边距 */
}

/* 调整 footer 的间距 */
.footer {
    margin-top: 0;
}

/* 响应式调整 */
@media (max-width: 768px) {
    .motivation {
        padding: 40px 0;
    }
    
    .section {
        padding: 40px 0;
    }
}