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

body {
    font-family: "Microsoft YaHei", "微软雅黑", "SimSun", "宋体", Arial, sans-serif;
    background: linear-gradient(135deg, #f5f7fa 0%, #e8f0f8 100%);
    color: #333;
    line-height: 1.6;
    min-height: 100vh;
}

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

.container {
    width: 1200px;
    max-width: 95%;
    margin: 0 auto;
}

.header {
    background: linear-gradient(135deg, #4A90A4 0%, #367588 100%);
    padding: 20px 0;
    box-shadow: 0 2px 15px rgba(74, 144, 164, 0.2);
}

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

.logo h1 {
    color: #fff;
    font-size: 28px;
    font-weight: bold;
    letter-spacing: 2px;
    text-shadow: 1px 1px 3px rgba(0,0,0,0.1);
}

.logo .slogan {
    color: rgba(255,255,255,0.9);
    font-size: 14px;
    margin-top: 5px;
}

.search-box form {
    display: flex;
}

.search-box input {
    width: 300px;
    padding: 10px 15px;
    border: none;
    border-radius: 20px 0 0 20px;
    font-size: 14px;
    outline: none;
    background: rgba(255,255,255,0.95);
}

.search-box button {
    padding: 10px 20px;
    background: #5BA3B8;
    color: #fff;
    border: none;
    border-radius: 0 20px 20px 0;
    cursor: pointer;
    font-size: 14px;
    transition: all 0.3s;
}

.search-box button:hover {
    background: #6fb8cc;
}

.nav {
    background: #fff;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

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

.nav li {
    position: relative;
}

.nav li a {
    display: block;
    padding: 16px 25px;
    color: #555;
    font-size: 15px;
    transition: all 0.3s;
}

.nav li:hover a,
.nav li.active a {
    color: #4A90A4;
    background: #f0f8fb;
}

.nav li.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, #4A90A4, #5BA3B8);
}

.main-banner {
    background: linear-gradient(135deg, #4A90A4 0%, #6FB8CC 50%, #A8D5E2 100%);
    padding: 50px 0;
    text-align: center;
    color: #fff;
}

.main-banner h2 {
    font-size: 32px;
    margin-bottom: 12px;
    letter-spacing: 2px;
    text-shadow: 1px 1px 3px rgba(0,0,0,0.1);
}

.main-banner p {
    font-size: 16px;
    opacity: 0.95;
}

.main-content {
    padding: 30px 0;
}

.section {
    margin-bottom: 40px;
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 12px;
    border-bottom: 2px solid #e0ebf0;
}

.section-header h3 {
    font-size: 20px;
    color: #333;
    position: relative;
    padding-left: 15px;
}

.section-header h3::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 4px;
    height: 22px;
    background: linear-gradient(180deg, #4A90A4, #6FB8CC);
    border-radius: 2px;
}

.more-link {
    color: #4A90A4;
    font-size: 14px;
    transition: all 0.3s;
}

.more-link:hover {
    color: #5BA3B8;
}

.category-list {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 20px;
}

.category-item {
    background: #fff;
    padding: 28px 20px;
    border-radius: 10px;
    text-align: center;
    border: 1px solid #e8f0f5;
    transition: all 0.3s;
    box-shadow: 0 2px 8px rgba(74, 144, 164, 0.05);
}

.category-item:hover {
    border-color: #4A90A4;
    box-shadow: 0 8px 25px rgba(74, 144, 164, 0.15);
    transform: translateY(-5px);
}

.category-icon {
    width: 65px;
    height: 65px;
    margin: 0 auto 15px;
    background: linear-gradient(135deg, #f0f8fb 0%, #e8f4f8 100%);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 28px;
    color: #4A90A4;
    transition: all 0.3s;
}

.category-item:hover .category-icon {
    background: linear-gradient(135deg, #4A90A4 0%, #6FB8CC 100%);
    color: #fff;
}

.category-item h4 {
    font-size: 16px;
    color: #333;
    margin-bottom: 8px;
}

.category-item p {
    font-size: 13px;
    color: #777;
    line-height: 1.5;
}

.course-list {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 25px;
}

.course-item {
    background: #fff;
    border-radius: 10px;
    overflow: hidden;
    border: 1px solid #e8f0f5;
    transition: all 0.3s;
    box-shadow: 0 2px 10px rgba(74, 144, 164, 0.06);
}

.course-item:hover {
    border-color: #4A90A4;
    box-shadow: 0 8px 25px rgba(74, 144, 164, 0.15);
    transform: translateY(-5px);
}

.course-cover {
    width: 100%;
    height: 170px;
    background: #f0f8fb;
}

.course-cover-placeholder {
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #A8D5E2 0%, #4A90A4 100%);
}

.course-cover-placeholder span {
    font-size: 52px;
    color: #fff;
    font-weight: bold;
    text-shadow: 1px 1px 3px rgba(0,0,0,0.1);
}

.course-cover img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

.course-info {
    padding: 16px;
}

.course-info h4 {
    font-size: 16px;
    color: #333;
    margin-bottom: 10px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.course-info .teacher {
    font-size: 13px;
    color: #4A90A4;
    margin-bottom: 8px;
}

.course-info .desc {
    font-size: 13px;
    color: #666;
    line-height: 1.6;
    height: 42px;
    overflow: hidden;
    margin-bottom: 12px;
}

.course-info .meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 12px;
    color: #888;
}

.category-tag {
    background: #f0f8fb;
    color: #4A90A4;
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 11px;
}

.views {
    color: #888;
}

.footer {
    background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
    color: #ccc;
    padding: 30px 0 20px;
    margin-top: 40px;
}

.footer-content {
    text-align: center;
    padding-bottom: 20px;
    border-bottom: 1px solid #465a6e;
    margin-bottom: 20px;
}

.footer-content p {
    font-size: 14px;
    line-height: 1.8;
    color: #aaa;
    max-width: 800px;
    margin: 0 auto;
}

.copyright {
    text-align: center;
    padding-top: 20px;
    font-size: 13px;
    color: #888;
}

.page-header {
    margin-bottom: 25px;
}

.page-header h2 {
    font-size: 24px;
    color: #333;
    margin-bottom: 10px;
}

.category-desc {
    color: #666;
    font-size: 14px;
}

.filter-bar {
    background: #fff;
    padding: 15px 20px;
    margin-bottom: 25px;
    border-radius: 8px;
    border: 1px solid #e8f0f5;
    box-shadow: 0 2px 8px rgba(74, 144, 164, 0.05);
}

.filter-bar span {
    color: #666;
    margin-right: 15px;
}

.filter-bar a {
    display: inline-block;
    padding: 6px 16px;
    margin-right: 10px;
    color: #666;
    border-radius: 20px;
    transition: all 0.3s;
    border: 1px solid transparent;
}

.filter-bar a:hover,
.filter-bar a.active {
    background: #4A90A4;
    color: #fff;
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    background: #fff;
    border-radius: 10px;
    border: 1px solid #e8f0f5;
    color: #888;
}

.empty-state p {
    font-size: 16px;
    margin-top: 15px;
}

.empty-tip {
    margin-top: 10px;
    font-size: 14px !important;
    color: #aaa !important;
}

.breadcrumb {
    padding: 15px 0;
    font-size: 14px;
    color: #666;
    border-bottom: 1px solid #e0ebf0;
    margin-bottom: 25px;
}

.breadcrumb a {
    color: #4A90A4;
}

.breadcrumb a:hover {
    color: #5BA3B8;
}

.course-detail {
    background: #fff;
    border-radius: 10px;
    border: 1px solid #e8f0f5;
    overflow: hidden;
    box-shadow: 0 2px 15px rgba(74, 144, 164, 0.08);
}

.course-header {
    display: flex;
    padding: 30px;
    background: linear-gradient(135deg, #f0f8fb 0%, #e8f4f8 100%);
}

.course-cover-large {
    width: 300px;
    flex-shrink: 0;
}

.course-cover-placeholder.large {
    width: 100%;
    height: 200px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #A8D5E2 0%, #4A90A4 100%);
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(74, 144, 164, 0.2);
}

.course-cover-placeholder.large span {
    font-size: 72px;
    color: #fff;
    font-weight: bold;
}

.course-cover-large img {
    width: 100%;
    height: 200px;
    object-fit: cover;
    border-radius: 10px;
    box-shadow: 0 4px 15px rgba(74, 144, 164, 0.2);
    display: block;
}

.course-header-info {
    flex: 1;
    padding-left: 30px;
}

.course-header-info h1 {
    font-size: 28px;
    color: #333;
    margin-bottom: 15px;
}

.course-header-info .teacher {
    font-size: 16px;
    color: #4A90A4;
    margin-bottom: 15px;
}

.course-header-info .desc {
    font-size: 15px;
    color: #666;
    line-height: 1.8;
    margin-bottom: 20px;
}

.stats {
    display: flex;
    gap: 40px;
}

.stat-item {
    text-align: center;
}

.stat-item strong {
    display: block;
    font-size: 26px;
    color: #4A90A4;
}

.stat-item span {
    font-size: 14px;
    color: #777;
}

.video-section {
    padding: 30px;
}

.video-section h3 {
    font-size: 18px;
    color: #333;
    margin-bottom: 20px;
    padding-bottom: 10px;
    border-bottom: 2px solid #e0ebf0;
}

.video-list {
    border: 1px solid #e8f0f5;
    border-radius: 8px;
    overflow: hidden;
}

.video-item {
    display: flex;
    align-items: center;
    padding: 18px 20px;
    border-bottom: 1px solid #f0f5f8;
    transition: background 0.3s;
}

.video-item:last-child {
    border-bottom: none;
}

.video-item:hover {
    background: #f8fbfd;
}

.video-index {
    width: 42px;
    height: 42px;
    background: linear-gradient(135deg, #4A90A4 0%, #6FB8CC 100%);
    color: #fff;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 16px;
    margin-right: 20px;
    flex-shrink: 0;
    font-weight: bold;
}

.video-info {
    flex: 1;
}

.video-info h4 {
    font-size: 16px;
    color: #333;
    margin-bottom: 5px;
}

.video-info p {
    font-size: 13px;
    color: #666;
}

.video-meta {
    text-align: right;
    flex-shrink: 0;
}

.video-meta .duration {
    display: block;
    font-size: 14px;
    color: #4A90A4;
    margin-bottom: 5px;
}

.video-meta .views {
    font-size: 12px;
    color: #999;
}

.player-page {
    display: grid;
    grid-template-columns: 1fr 300px;
    gap: 25px;
}

.player-section {
    background: #fff;
    border-radius: 10px;
    border: 1px solid #e8f0f5;
    overflow: hidden;
    box-shadow: 0 2px 15px rgba(74, 144, 164, 0.08);
}

.video-title {
    padding: 20px;
    border-bottom: 1px solid #e8f0f5;
}

.video-title h1 {
    font-size: 22px;
    color: #333;
    margin-bottom: 10px;
}

.video-meta-info {
    font-size: 14px;
    color: #666;
}

.video-player-wrapper {
    position: relative;
    width: 100%;
    height: 450px;
    background: #000;
    border-radius: 8px;
    overflow: hidden;
}

.player-container {
    width: 100%;
    height: 100%;
    background: #000;
    cursor: pointer;
}

.player-container::-webkit-media-controls {
    display: none;
}

.custom-controls-wrapper {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 10;
}

.custom-controls {
    position: relative;
    background: linear-gradient(transparent, rgba(0,0,0,0.8));
    padding: 10px;
    transition: opacity 0.3s ease;
}

.controls-top {
    margin-bottom: 10px;
}

.progress-container {
    width: 100%;
    height: 5px;
    background: rgba(255,255,255,0.3);
    cursor: pointer;
    border-radius: 3px;
    position: relative;
}

.progress-container:hover {
    height: 7px;
}

.progress-bar {
    width: 100%;
    height: 100%;
    position: relative;
    border-radius: 3px;
}

.progress-buffered {
    position: absolute;
    height: 100%;
    background: rgba(255,255,255,0.5);
    border-radius: 3px;
    width: 0%;
}

.progress-filled {
    position: absolute;
    height: 100%;
    background: #4A90A4;
    border-radius: 3px;
    width: 0%;
    transition: width 0.1s linear;
}

.time-preview {
    position: absolute;
    bottom: 30px;
    background: rgba(0,0,0,0.8);
    color: #fff;
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 12px;
    transform: translateX(-50%);
    pointer-events: none;
}

.controls-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.controls-left, .controls-right {
    display: flex;
    align-items: center;
    gap: 10px;
}

.control-btn {
    background: none;
    border: none;
    color: #fff;
    cursor: pointer;
    padding: 8px 12px;
    border-radius: 4px;
    transition: all 0.2s;
    font-size: 16px;
}

.control-btn:hover {
    background: rgba(255,255,255,0.2);
}

.volume-container {
    display: flex;
    align-items: center;
    gap: 5px;
    position: relative;
}

.volume-slider-container {
    width: 0;
    overflow: hidden;
    transition: width 0.3s ease;
}

.volume-container:hover .volume-slider-container {
    width: 80px;
}

.volume-slider {
    width: 80px;
    height: 4px;
    -webkit-appearance: none;
    background: rgba(255,255,255,0.3);
    border-radius: 2px;
    outline: none;
}

.volume-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 12px;
    height: 12px;
    background: #fff;
    border-radius: 50%;
    cursor: pointer;
}

.time-display {
    color: #fff;
    font-size: 14px;
    font-family: "Microsoft YaHei", sans-serif;
    white-space: nowrap;
    min-width: 120px;
}

.time-separator {
    margin: 0 5px;
    opacity: 0.7;
}

.current-time, .duration {
    display: inline-block;
    min-width: 45px;
}

.playback-rate-container {
    position: relative;
}

.rate-btn span {
    font-size: 14px;
}

.rate-options {
    position: absolute;
    bottom: 100%;
    right: 0;
    background: rgba(0,0,0,0.9);
    border-radius: 6px;
    padding: 5px 0;
    display: none;
    min-width: 70px;
}

.rate-options.show {
    display: block;
}

.rate-options div {
    color: #fff;
    padding: 8px 15px;
    cursor: pointer;
    font-size: 14px;
    transition: background 0.2s;
}

.rate-options div:hover {
    background: rgba(255,255,255,0.2);
}

.rate-options div.active {
    color: #4A90A4;
    font-weight: bold;
}

.fullscreen-btn {
    margin-left: 5px;
}

#videoPlayerContainer:fullscreen .player-container {
    height: 100%;
    border-radius: 0;
}

#videoPlayerContainer:fullscreen {
    height: 100vh;
}

.video-desc {
    padding: 20px;
    border-bottom: 1px solid #e8f0f5;
}

.video-desc h3 {
    font-size: 16px;
    color: #333;
    margin-bottom: 10px;
}

.video-desc p {
    font-size: 14px;
    color: #666;
    line-height: 1.8;
}

.course-info-card {
    padding: 20px;
}

.course-info-card h3 {
    font-size: 16px;
    color: #333;
    margin-bottom: 15px;
}

.course-link {
    display: flex;
    align-items: center;
    padding: 15px;
    background: linear-gradient(135deg, #f0f8fb 0%, #e8f4f8 100%);
    border-radius: 8px;
    transition: all 0.3s;
    border: 1px solid #e8f0f5;
}

.course-link:hover {
    background: linear-gradient(135deg, #e8f4f8 0%, #d8eef5 100%);
    border-color: #4A90A4;
}

.course-mini-cover {
    width: 60px;
    height: 45px;
    background: linear-gradient(135deg, #A8D5E2 0%, #4A90A4 100%);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-right: 15px;
}

.course-mini-cover span {
    color: #fff;
    font-size: 20px;
    font-weight: bold;
}

.course-mini-cover-img {
    width: 60px;
    height: 45px;
    object-fit: cover;
    border-radius: 6px;
    margin-right: 15px;
    display: block;
}

.course-mini-info h4 {
    font-size: 15px;
    color: #333;
    margin-bottom: 5px;
}

.course-mini-info p {
    font-size: 13px;
    color: #666;
}

.sidebar {
    background: #fff;
    border-radius: 10px;
    border: 1px solid #e8f0f5;
    padding: 20px;
    height: fit-content;
    box-shadow: 0 2px 15px rgba(74, 144, 164, 0.08);
}

.sidebar h3 {
    font-size: 16px;
    color: #333;
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 2px solid #e0ebf0;
}

.related-videos {
    max-height: 500px;
    overflow-y: auto;
}

.related-video-item {
    display: block;
    padding: 12px 0;
    border-bottom: 1px dashed #e8f0f5;
    transition: all 0.3s;
}

.related-video-item:last-child {
    border-bottom: none;
}

.related-video-item:hover {
    color: #4A90A4;
    padding-left: 8px;
}

.rv-title {
    font-size: 14px;
    margin-bottom: 5px;
    line-height: 1.4;
}

.rv-duration {
    font-size: 12px;
    color: #999;
}

.no-more {
    text-align: center;
    color: #888;
    font-size: 14px;
    padding: 20px 0;
}

.search-keyword {
    color: #4A90A4;
    font-size: 14px;
}

.search-video-list {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
}

.search-video-item {
    background: #fff;
    padding: 20px;
    border-radius: 8px;
    border: 1px solid #e8f0f5;
    transition: all 0.3s;
    box-shadow: 0 2px 8px rgba(74, 144, 164, 0.05);
}

.search-video-item:hover {
    border-color: #4A90A4;
    box-shadow: 0 6px 20px rgba(74, 144, 164, 0.12);
}

.sv-info h4 {
    font-size: 16px;
    color: #333;
    margin-bottom: 10px;
}

.sv-info p {
    font-size: 13px;
    color: #666;
    line-height: 1.6;
    margin-bottom: 10px;
}

.sv-meta {
    font-size: 12px;
    color: #888;
}

.sv-meta span {
    margin-right: 15px;
}

@media (max-width: 1024px) {
    .course-list {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .category-list {
        grid-template-columns: repeat(3, 1fr);
    }
    
    .player-page {
        grid-template-columns: 1fr;
    }
    
    .sidebar {
        margin-top: 20px;
    }
    
    .search-video-list {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .header .container {
        flex-direction: column;
        gap: 15px;
    }
    
    .nav ul {
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .nav li a {
        padding: 12px 15px;
        font-size: 14px;
    }
    
    .course-list {
        grid-template-columns: 1fr;
    }
    
    .category-list {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .course-header {
        flex-direction: column;
    }
    
    .course-cover-large {
        width: 100%;
        margin-bottom: 20px;
    }
    
    .course-header-info {
        padding-left: 0;
    }
    
    .main-banner h2 {
        font-size: 24px;
    }
    
    .main-banner p {
        font-size: 14px;
    }
}