/* 全局变量 */
:root {
    --primary-color: #1890ff;
    --secondary-color: #52c41a;
    --text-color: #333;
    --light-gray: #f5f5f5;
    --dark-gray: #666;
}

/* 全局样式 */
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial;
    color: var(--text-color);
    line-height: 1.6;
    padding-top: 76px; /* 为固定导航栏留出空间 */
}

/* 导航栏样式 */
.navbar {
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.navbar-brand img {
    transition: transform 0.3s;
}

.navbar-brand img:hover {
    transform: scale(1.05);
}

/* 轮播图样式 */
.carousel {
    margin-top: -76px; /* 抵消导航栏的padding-top */
}

.carousel-item {
    height: 600px;
}

.carousel-item img {
    object-fit: cover;
    height: 100%;
}

.carousel-caption {
    background: rgba(0, 0, 0, 0.5);
    padding: 2rem;
    border-radius: 10px;
}

.carousel-caption h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

/* 课程分类卡片样式 */
.category-card {
    background: white;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    transition: transform 0.3s;
}

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

.category-card img {
    width: 100%;
    height: 200px;
    object-fit: cover;
}

.category-card h3 {
    padding: 1rem;
    margin: 0;
    font-size: 1.25rem;
}

.category-card p {
    padding: 0 1rem 1rem;
    margin: 0;
    color: var(--dark-gray);
}

/* 热门课程样式 */
.popular-courses {
    background-color: var(--light-gray);
}

/* 页脚样式 */
footer {
    background-color: #343a40;
}

footer a {
    text-decoration: none;
    transition: color 0.3s;
}

footer a:hover {
    color: var(--primary-color) !important;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .carousel-item {
        height: 400px;
    }
    
    .carousel-caption h2 {
        font-size: 1.8rem;
    }
    
    .category-card img {
        height: 150px;
    }
}

/* 按钮样式 */
.btn-primary {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    padding: 0.5rem 1.5rem;
    transition: all 0.3s;
}

.btn-primary:hover {
    background-color: #40a9ff;
    border-color: #40a9ff;
    transform: translateY(-2px);
}

.btn-outline-primary {
    color: var(--primary-color);
    border-color: var(--primary-color);
    padding: 0.5rem 1.5rem;
    transition: all 0.3s;
}

.btn-outline-primary:hover {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    transform: translateY(-2px);
}