/* 原始CSS样式保持不变 */
:root {
    --antd-color-8: #ad6800;
    --antd-color-7: #d48806;
    --antd-color-6: #faad14;
    --antd-color-5: #ffc53d;
    --antd-color-4: #ffd666;
    --antd-color-3: #ffe58f;
    --antd-color-2: #fff1b8;
}

html,
body,
.container {
    margin: 0;
    padding: 0;
    width: 100vw;
    height: 100vh;
    overflow: hidden;
    /* background: #eff2f9; */
    background-image: url(../asset/bg.png);
    background-repeat: no-repeat;
    background-size: 100%;
}

.container-header {
    position: fixed;
    top: 0px;
    left: 0px;
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: rgba(255, 255, 255, 0.9);
    box-shadow: rgba(0, 0, 0, 0.1) 0px 2px 10px;
    z-index: 1000;
    padding: 10px 20px;
}

.container-header-logo {
    display: flex;
    align-items: center;
}

.container-header-nav {
    display: flex;
    margin-right: 50px;
}

.container-header-nav>div {
    text-align: center;
    margin-right: 10px;
    color: rgb(0, 0, 0);
    font-weight: 500;
    font-size: 16px;
    text-decoration: none;
    padding: 5px 20px;
    border-radius: 20px;
    transition: 0.3s;
    border: 1px solid transparent;
    cursor: pointer;
}

.container-header-nav>div:hover {
    border: 1px solid #999;
}

.container-header-nav>div.active {
    background-color: transparent;
    color: #000;
    border: 1px solid #000;
}

.breadcrumb {
    position: fixed;
    top: 75px;
    left: 0;
    right: 0;
    /* background: #eff2f9; */
    backdrop-filter: blur(10px);
    padding: 15px 20px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
    z-index: 999;
    font-family: inherit;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    animation: slideInDown 0.6s ease-out;
}

@keyframes slideInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.breadcrumb-content {
    color: #6c757d;
    font-size: 18px;
    font-weight: 500;
    display: flex;
    align-items: center;
    justify-content: space-between;
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 20px;
}

.breadcrumb-content a {
    color: var(--antd-color-6);
    text-decoration: none;
    font-weight: 600;
    position: relative;
    padding: 4px 8px;
    border-radius: 6px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.breadcrumb-content a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 2px;
    background: var(--antd-color-6);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    transform: translateX(-50%);
}

.breadcrumb-content a:hover::after {
    width: 80%;
}

.search-container {
    position: relative;
}

.search-input {
    padding: 8px 35px 8px 12px;
    border: 2px solid #ddd;
    border-radius: 20px;
    outline: none;
    width: 150px;
    font-size: 14px;
    background: rgba(255, 255, 255, 0.9);
    transition: all 0.3s ease;
    color: #333;
}

.search-input::placeholder {
    color: #999;
}

.breadcrumb-path {
    display: flex;
    align-items: center;
}

.breadcrumb-path a {
    color: #000;  /* 默认黑色 */
    text-decoration: none;
    font-weight: 500;
    position: relative;
    padding: 4px 8px;
    border-radius: 6px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.breadcrumb-path a:hover {
    color: #faad14;
}

.breadcrumb-path a.active {
    color: #faad14;  /* 选中状态为 #faad14 */
    font-weight: 600;
}

.breadcrumb-path span {
    margin: 0 8px;
    opacity: 0.6;
    color: #666;
}

/* 搜索框样式 */
.search-container {
    position: relative;
}

.search-input {
    padding: 8px 35px 8px 12px;
    border: 2px solid #ddd;
    border-radius: 20px;
    outline: none;
    width: 150px;
    font-size: 14px;
    background: rgba(255, 255, 255, 0.9);
    transition: all 0.3s ease;
    color: #333;
}

.search-input::placeholder {
    color: #999;
}

.search-input:focus {
    border-color: #faad14;
    box-shadow: 0 0 0 2px rgba(250, 173, 20, 0.1);
    width: 180px;
}

.search-icon {
    position: absolute;
    right: 10px;
    top: 50%;
    transform: translateY(-50%);
    width: 16px;
    height: 16px;
    pointer-events: none;
    opacity: 0.6;
    color: #666;
}

.search-input:focus + .search-icon {
    opacity: 1;
    color: #faad14;
}

/* 主要内容区域 */
.main-content {
    display: flex;
    margin: 140px auto 20px auto;
    height: calc(100vh - 160px);
    font-family: inherit;
    max-width: 1400px;
    padding: 0 20px;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: 12px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    animation: fadeInUp 0.8s ease-out;
    overflow: hidden;
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* 左侧边栏 */
.sidebar {
    width: 280px;
    background: linear-gradient(145deg, #ffffff 0%, #f8f9fa 100%);
    border-right: 1px solid rgba(233, 236, 239, 0.3);
    overflow-y: auto;
    border-radius: 12px 0 0 12px;
    animation: slideInLeft 0.6s ease-out 0.2s both;
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-20px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.sidebar-title {
    padding: 20px;
    font-size: 18px;
    font-weight: 700;
    color: #343a40;
    border-bottom: 1px solid rgba(233, 236, 239, 0.5);
    background: linear-gradient(90deg, var(--antd-color-6), var(--antd-color-8));
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    position: relative;
}

.sidebar-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 20px;
    right: 20px;
    height: 3px;
    background: linear-gradient(90deg, var(--antd-color-6), var(--antd-color-8));
    border-radius: 2px;
}

.sidebar-menu {
    list-style: none;
    padding: 10px 0;
    margin: 0;
}

.sidebar-menu li {
    margin: 5px 10px;
    border-radius: 8px;
    overflow: hidden;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.sidebar-menu li:hover {
    transform: translateX(5px);
}

.sidebar-menu li a {
    display: block;
    padding: 15px 20px;
    color: #343a40;
    text-decoration: none;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    font-size: 14px;
    font-weight: 500;
    border-radius: 8px;
    position: relative;
    overflow: hidden;
}

.sidebar-menu li a::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.sidebar-menu li a:hover::before {
    left: 100%;
}

.sidebar-menu li a:hover {
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    color: var(--antd-color-6);
    box-shadow: 0 2px 10px rgba(0, 123, 255, 0.1);
}

.sidebar-menu li.active a {
    background: linear-gradient(135deg, var(--antd-color-5), var(--antd-color-7));
    color: white;
    font-weight: 600;
    box-shadow: 0 4px 15px var(--antd-color-2);
}

/* 右侧内容区域 */
.content-area {
    flex: 1;
    padding: 20px;
    overflow-y: auto;
    background: transparent;
    animation: slideInRight 0.6s ease-out 0.4s both;
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(20px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

/* 筛选区域 */
.filter-section {
    background: linear-gradient(145deg, #ffffff 0%, #f8f9fa 100%);
    padding: 25px;
    border-radius: 12px;
    margin-bottom: 25px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(10px);
    animation: fadeInScale 0.6s ease-out 0.6s both;
    position: relative;
    overflow: hidden;
}

@keyframes fadeInScale {
    from {
        opacity: 0;
        transform: scale(0.95);
    }

    to {
        opacity: 1;
        transform: scale(1);
    }
}

.filter-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--antd-color-6), var(--antd-color-8), var(--antd-color-4));
}

.filter-row {
    display: flex;
    align-items: center;
    margin-bottom: 20px;
    flex-wrap: wrap;
    animation: slideInUp 0.5s ease-out forwards;
}

@keyframes slideInUp {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.filter-row:last-child {
    margin-bottom: 0;
}

.filter-label {
    min-width: 80px;
    font-weight: 700;
    color: #343a40;
    margin-right: 20px;
    font-size: 15px;
    position: relative;
}

.filter-label::after {
    content: '';
    position: absolute;
    right: -10px;
    top: 50%;
    width: 2px;
    height: 20px;
    background: linear-gradient(to bottom, var(--antd-color-6), transparent);
    transform: translateY(-50%);
}

.filter-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.filter-tag {
    padding: 8px 18px;
    background: linear-gradient(145deg, #ffffff, #f8f9fa);
    color: #6c757d;
    border: 2px solid transparent;
    border-radius: 25px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.filter-tag::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.4), transparent);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.filter-tag:hover::before {
    left: 100%;
}

.filter-tag:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.15);
    border-color: var(--antd-color-6);
}

.filter-tag.active {
    background: linear-gradient(135deg, var(--antd-color-5), var(--antd-color-7));
    color: white;
    border-color: var(--antd-color-6);
    box-shadow: 0 4px 20px var(--antd-color-3);
    transform: translateY(-1px);
}

/* 教材展示区域 - 学期卡片 */
.materials-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(420px, 1fr));
    gap: 30px;
    animation: staggerFadeIn 0.8s ease-out 0.8s both;
}

@keyframes staggerFadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

.material-card {
    background: linear-gradient(145deg, #ffffff 0%, #f8f9fa 100%);
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
    position: relative;
    overflow: hidden;
    border: 1px solid rgba(255, 255, 255, 0.2);
    animation: cardSlideIn 0.6s ease-out forwards;
}

@keyframes cardSlideIn {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.95);
    }

    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

.material-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: linear-gradient(90deg, var(--antd-color-6), var(--antd-color-8));
    transform: scaleX(0);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.material-card:hover::before {
    transform: scaleX(1);
}

.material-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.2);
}

.material-cover {
    display: flex;
    align-items: center;
    margin-bottom: 25px;
}

.material-image {
    width: 130px;
    height: 160px;
    border-radius: 12px;
    margin-right: 25px;
    position: relative;
    overflow: hidden;
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);

    /* 添加默认的渐变背景 */
    background-color: var(--antd-color-2);
    background-image: linear-gradient(135deg, var(--antd-color-3) 0%, var(--antd-color-5) 100%);
}

.material-image::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 50px;
    height: 50px;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="white" stroke-width="2"><path d="M2 3h6a4 4 0 0 1 4 4v14a3 3 0 0 0-3-3H2z"/><path d="M22 3h-6a4 4 0 0 0-4 4v14a3 3 0 0 1 3-3h7z"/></svg>') center/contain no-repeat;
    opacity: 0.4;
    pointer-events: none;
    z-index: 1;
}

/* 当背景图片加载成功时，隐藏默认图标 */
.material-image[style*="background-image: url"]::before {
    display: none;
}

.material-image::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, transparent 60%, rgba(0, 123, 255, 0.1));
    opacity: 0;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.material-card:hover .material-image::after {
    opacity: 1;
}

.material-card:hover .material-image {
    transform: scale(1.05);
}

.material-info h3 {
    margin: 0 0 15px 0;
    font-size: 20px;
    font-weight: 700;
    color: #343a40;
    line-height: 1.4;
    background: linear-gradient(135deg, var(--antd-color-7), var(--antd-color-5));
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.material-meta {
    display: flex;
    align-items: center;
    gap: 15px;
    font-size: 14px;
    color: #6c757d;
    font-weight: 500;
}

.material-meta span {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 4px 10px;
    background: rgba(0, 123, 255, 0.1);
    border-radius: 15px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.material-meta span:hover {
    background: rgba(0, 123, 255, 0.2);
    transform: scale(1.05);
}

.material-meta .icon {
    width: 16px;
    height: 16px;
    background: linear-gradient(135deg, var(--antd-color-6), var(--antd-color-4));
    border-radius: 50%;
}

.course-stats {
    font-size: 15px;
    color: #6c757d;
    margin-top: 18px;
    font-weight: 500;
    padding: 10px 15px;
    background: linear-gradient(135deg, rgba(0, 123, 255, 0.05), rgba(108, 117, 125, 0.05));
    border-radius: 8px;
    border-left: 4px solid var(--antd-color-6);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.material-card:hover .course-stats {
    background: linear-gradient(135deg, rgba(0, 123, 255, 0.1), rgba(108, 117, 125, 0.1));
    transform: translateX(5px);
}

/* 新增：课程列表展示区域 - 课程卡片 */
.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
    animation: staggerFadeIn 0.8s ease-out 0.8s both;
}

/* 返回按钮样式 */
.back-button {
    grid-column: 1 / -1;
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 20px;
    background: linear-gradient(135deg, var(--antd-color-5), var(--antd-color-7));
    color: white;
    border-radius: 25px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: 0 4px 15px var(--antd-color-3);
    margin-bottom: 20px;
    width: fit-content;
}

.back-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 25px var(--antd-color-3);
    background: linear-gradient(135deg, var(--antd-color-7), var(--antd-color-5));
}

.back-button svg {
    width: 18px;
    height: 18px;
}

/* 课程卡片样式 - 比学期卡片更小 */
.course-card {
    background: linear-gradient(145deg, #ffffff 0%, #f8f9fa 100%);
    border-radius: 10px;
    padding: 20px;
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.08);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
    position: relative;
    overflow: hidden;
    border: 1px solid rgba(255, 255, 255, 0.2);
    animation: courseCardSlideIn 0.5s ease-out forwards;
}

@keyframes courseCardSlideIn {
    from {
        opacity: 0;
        transform: translateY(15px) scale(0.95);
    }

    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

.course-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--antd-color-6), var(--antd-color-8));
    transform: scaleX(0);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.course-card:hover::before {
    transform: scaleX(1);
}

.course-card:hover {
    transform: translateY(-5px) scale(1.02);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
}

.course-card.disabled {
    opacity: 0.6;
    cursor: pointer;
}

.course-card.disabled:hover {
    transform: none;
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.08);
}

.course-cover {
    display: flex;
    flex-direction: column;
    height: 100%;
}

.course-image {
    width: 100%;
    height: 120px;
    border-radius: 8px;
    margin-bottom: 15px;
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    background-color: var(--antd-color-2);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;

    /* 添加默认的渐变背景，当图片加载失败时显示 */
    background-image: linear-gradient(135deg, var(--antd-color-3) 0%, var(--antd-color-5) 100%);
}

.course-image::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 40px;
    height: 40px;
    background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="white" stroke-width="2"><path d="M14 2H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h12a2 2 0 0 0 2-2V8z"/><polyline points="14,2 14,8 20,8"/><line x1="16" y1="13" x2="8" y2="13"/><line x1="16" y1="17" x2="8" y2="17"/><polyline points="10,9 9,9 8,9"/></svg>') center/contain no-repeat;
    opacity: 0.3;
    pointer-events: none;
}

/* 当背景图片加载成功时，隐藏默认图标 */
.course-image[style*="background-image: url"]::before {
    display: none;
}

.course-image::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, transparent 60%, rgba(250, 173, 20, 0.1));
    opacity: 0;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.course-card:hover .course-image::after {
    opacity: 1;
}

.course-card:hover .course-image {
    transform: scale(1.02);
}

.course-info {
    flex: 1;
    display: flex;
    flex-direction: column;
}

.course-info h4 {
    margin: 0 0 10px 0;
    font-size: 16px;
    font-weight: 600;
    color: #343a40;
    line-height: 1.3;
    background: linear-gradient(135deg, var(--antd-color-7), var(--antd-color-5));
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.course-description {
    margin: 0 0 12px 0;
    font-size: 13px;
    color: #6c757d;
    line-height: 1.4;
    flex: 1;
}

.course-meta {
    margin-bottom: 12px;
}

.course-id {
    font-size: 12px;
    color: #999;
    background: rgba(0, 123, 255, 0.1);
    padding: 3px 8px;
    border-radius: 10px;
    display: inline-block;
}

.course-action {
    font-size: 13px;
    color: #6c757d;
    font-weight: 500;
    padding: 8px 12px;
    background: linear-gradient(135deg, rgba(250, 173, 20, 0.05), rgba(108, 117, 125, 0.05));
    border-radius: 6px;
    border-left: 3px solid var(--antd-color-6);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    text-align: center;
}

.course-card:hover .course-action {
    background: linear-gradient(135deg, rgba(250, 173, 20, 0.1), rgba(108, 117, 125, 0.1));
    transform: translateY(-1px);
}

/* 空课程样式 */
.empty-course {
    grid-column: 1 / -1;
    text-align: center;
    padding: 60px 20px;
    color: #6c757d;
}

.empty-content h3 {
    margin: 0 0 10px 0;
    font-size: 20px;
    color: #343a40;
}

.empty-content p {
    margin: 0;
    font-size: 14px;
    opacity: 0.8;
}

/* 自定义滚动条 */
.sidebar::-webkit-scrollbar,
.content-area::-webkit-scrollbar {
    width: 6px;
}

.sidebar::-webkit-scrollbar-track,
.content-area::-webkit-scrollbar-track {
    background: rgba(248, 249, 250, 0.5);
    border-radius: 3px;
}

.sidebar::-webkit-scrollbar-thumb,
.content-area::-webkit-scrollbar-thumb {
    background: linear-gradient(135deg, var(--antd-color-6), var(--antd-color-8));
    border-radius: 3px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.sidebar::-webkit-scrollbar-thumb:hover,
.content-area::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(135deg, var(--antd-color-8), var(--antd-color-4));
}

/* 响应式优化 */
@media (max-width: 768px) {
    .main-content {
        flex-direction: column;
        margin: 120px 10px 10px 10px;
        height: calc(100vh - 130px);
    }

    .sidebar {
        width: 100%;
        height: auto;
        border-right: none;
        border-bottom: 1px solid rgba(255, 255, 255, 0.2);
        border-radius: 12px 12px 0 0;
    }

    .materials-grid {
        grid-template-columns: 1fr;
        gap: 20px;
    }

    .course-grid {
        grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
        gap: 15px;
    }

    .material-cover {
        flex-direction: column;
        text-align: center;
    }

    .material-image {
        margin-right: 0;
        margin-bottom: 15px;
    }
}

/* 加载动画 */
@keyframes pulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.5;
    }
}

.loading {
    animation: pulse 1.5s ease-in-out infinite;
}