/* 全局样式重置 */
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
        }

        /* 科技感变量 - 调整为更明亮的配色 */
        :root {
            --primary: #1a2435; /* 主背景调亮 */
            --secondary: #2dd4bf; /* 亮色主调更清新 */
            --accent: #8b5cf6; /* 强调色稍亮 */
            --light: #e0f2fe; /* 浅色文字更亮 */
            --dark: #0f172a; /* 深色背景稍亮 */
            --gradient-primary: linear-gradient(135deg, #1e293b 0%, #334155 100%); /* 渐变更明亮 */
            --gradient-secondary: linear-gradient(135deg, #27374d 0%, #475569 100%);
            --gradient-glow: linear-gradient(90deg, #2dd4bf, #8b5cf6);
            --shadow: 0 10px 40px rgba(45, 212, 191, 0.3); /* 阴影更明显 */
            --shadow-strong: 0 0 30px rgba(139, 92, 246, 0.4);
            --border-glow: 0 0 15px rgba(45, 212, 191, 0.6);
        }

        body {
            background-color: var(--primary);
            color: #fff;
            overflow-x: hidden;
            background-image: 
                radial-gradient(circle at 20% 30%, rgba(139, 92, 246, 0.25) 0%, transparent 40%),
                radial-gradient(circle at 80% 70%, rgba(45, 212, 191, 0.2) 0%, transparent 40%);
            background-attachment: fixed;
        }

        /* 网格背景 - 调亮 */
        .grid-bg {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            z-index: -2;
            background-image: 
                linear-gradient(rgba(45, 212, 191, 0.2) 1px, transparent 1px),
                linear-gradient(90deg, rgba(45, 212, 191, 0.2) 1px, transparent 1px);
            background-size: 50px 50px;
            opacity: 0.4; /* 提高透明度让网格更明显 */
        }

        /* 导航栏样式 */
        nav {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 1.2rem 5%;
            background: rgba(26, 36, 53, 0.95); /* 稍亮的背景 */
            backdrop-filter: blur(15px);
            position: sticky;
            top: 0;
            z-index: 100;
            border-bottom: 1px solid rgba(45, 212, 191, 0.3); /* 边框更明显 */
            box-shadow: 0 0 20px rgba(45, 212, 191, 0.2);
        }

        .logo {
            font-size: 1.8rem;
            font-weight: 800;
            background: var(--gradient-glow);
            -webkit-background-clip: text;
            background-clip: text;
            color: transparent;
            display: flex;
            align-items: center;
            gap: 0.8rem;
            letter-spacing: 0.5px;
        }

        .logo i {
            font-size: 2rem;
            color: var(--secondary);
            filter: drop-shadow(0 0 8px rgba(45, 212, 191, 0.7)); /* 发光效果更亮 */
        }

        .nav-links {
            display: flex;
            gap: 2.5rem;
        }

        .nav-links a {
            color: #f0f0f0; /* 导航文字更亮 */
            text-decoration: none;
            transition: all 0.3s ease;
            position: relative;
            font-weight: 500;
            padding: 0.5rem 0;
        }

        .nav-links a::after {
            content: '';
            position: absolute;
            width: 0;
            height: 2px;
            bottom: 0;
            left: 0;
            background: var(--gradient-glow);
            transition: width 0.3s ease;
        }

        .nav-links a:hover {
            color: var(--secondary);
            text-shadow: 0 0 10px rgba(45, 212, 191, 0.6);
        }

        .nav-links a:hover::after {
            width: 100%;
        }

        .btn {
            background: var(--gradient-glow);
            color: #0f172a; /* 按钮文字稍深 */
            padding: 0.7rem 2rem;
            border-radius: 6px;
            text-decoration: none;
            font-weight: 700;
            transition: all 0.3s ease;
            border: none;
            cursor: pointer;
            box-shadow: 0 5px 15px rgba(139, 92, 246, 0.4);
            letter-spacing: 0.5px;
            display: inline-block;
        }

        .btn:hover {
            transform: translateY(-3px);
            box-shadow: var(--shadow-strong);
            filter: brightness(1.1);
        }

        /* 课程详情页面主体 */
        .course-detail-container {
            padding: 2rem 5%;
            max-width: 1400px;
            margin: 0 auto;
            display: grid;
            grid-template-columns: 70% 30%;
            gap: 2rem;
        }

        /* 课程主内容区 */
        .course-main {
            display: flex;
            flex-direction: column;
            gap: 2rem;
        }

        /* 课程头部信息 */
        .course-header {
            background: rgba(30, 41, 59, 0.8); /* 背景更亮 */
            border-radius: 15px;
            padding: 2rem;
            border: 1px solid rgba(45, 212, 191, 0.25); /* 边框更明显 */
            backdrop-filter: blur(10px);
        }

        .course-breadcrumb {
            display: flex;
            gap: 0.5rem;
            margin-bottom: 1rem;
            font-size: 0.9rem;
            color: var(--light);
            opacity: 0.9; /* 提高透明度 */
        }

        .course-breadcrumb a {
            color: var(--secondary);
            text-decoration: none;
        }

        .course-breadcrumb a:hover {
            text-decoration: underline;
        }s

        .course-title-section {
            /* margin-bottom: 1.5rem; */
        }

        .course-title {
            font-size: 2.2rem;
            margin-bottom: 0.8rem;
            color: var(--secondary);
            text-shadow: 0 0 10px rgba(45, 212, 191, 0.3);
        }

        .course-subtitle {
            color: var(--light);
            font-size: 1.1rem;
            opacity: 1; /* 完全不透明 */
            line-height: 1.6;
        }

        .course-meta-header {
            display: flex;
            flex-wrap: wrap;
            gap: 1.5rem;
            padding: 1rem 0;
            border-top: 1px solid rgba(45, 212, 191, 0.2);
            border-bottom: 1px solid rgba(45, 212, 191, 0.2);
        }

        .meta-header-item {
            display: flex;
            align-items: center;
            gap: 0.6rem;
            color: var(--light);
        }

        .meta-header-item i {
            color: var(--secondary);
            font-size: 1.2rem;
        }

        .meta-header-item .rating {
            color: #fbbf24; /* 评分星星更亮 */
            font-weight: 600;
        }

        /* 课程视频预览 */
        .course-video {
            background: rgba(30, 41, 59, 0.8);
            border-radius: 15px;
            padding: 1.5rem;
            border: 1px solid rgba(45, 212, 191, 0.25);
            backdrop-filter: blur(10px);
        }

        .video-container {
            width: 100%;
            height: 400px;
            background: #1e293b; /* 视频背景稍亮 */
            border-radius: 10px;
            overflow: hidden;
            display: flex;
            align-items: center;
            justify-content: center;
            position: relative;
        }

        .video-placeholder {
            width: 100%;
            height: 100%;
            object-fit: cover;
            opacity: 1; /* 封面完全不透明 */
        }

        /* 课程内容标签页 */
        .course-tabs {
            background: rgba(30, 41, 59, 0.8);
            border-radius: 15px;
            border: 1px solid rgba(45, 212, 191, 0.25);
            backdrop-filter: blur(10px);
            overflow: hidden;
        }

        .tabs-nav {
            display: flex;
            border-bottom: 1px solid rgba(45, 212, 191, 0.25);
        }

        .tab-btn {
            padding: 1.2rem 2rem;
            background: transparent;
            border: none;
            color: var(--light);
            font-size: 1rem;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            position: relative;
        }

        .tab-btn.active {
            color: var(--secondary);
        }

        .tab-btn.active::after {
            content: '';
            position: absolute;
            bottom: 0;
            left: 0;
            width: 100%;
            height: 3px;
            background: var(--gradient-glow);
        }

        .tab-btn:hover:not(.active) {
            color: var(--secondary);
            background: rgba(45, 212, 191, 0.1);
        }

        .tabs-content {
            padding: 2rem;
        }

        .tab-content {
            display: none;
        }

        .tab-content.active {
            display: block;
            animation: fadeIn 0.5s ease;
        }

        @keyframes fadeIn {
            from { opacity: 0; }
            to { opacity: 1; }
        }

        /* 课程介绍 */
        .course-description h3 {
            color: var(--secondary);
            font-size: 1.5rem;
            margin-bottom: 1rem;
        }

        .course-description p {
            color: var(--light);
            line-height: 1.8;
            margin-bottom: 1.2rem;
            font-size: 1.05rem;
            opacity: 1; /* 文字完全不透明 */
        }

        .course-features {
            display: grid;
            grid-template-columns: repeat(2, 1fr);
            gap: 1rem;
            margin: 2rem 0;
        }

        .feature-item {
            display: flex;
            align-items: flex-start;
            gap: 0.8rem;
        }

        .feature-item i {
            color: var(--secondary);
            font-size: 1.2rem;
            margin-top: 0.2rem;
        }

        .feature-item div {
            color: var(--light);
            line-height: 1.6;
            opacity: 1;
        }

        .course-objectives h3 {
            color: var(--secondary);
            font-size: 1.5rem;
            margin-bottom: 1rem;
        }

        .objectives-list {
            list-style: none;
        }

        .objectives-list li {
            padding: 0.8rem 0;
            border-bottom: 1px solid rgba(45, 212, 191, 0.2);
            display: flex;
            align-items: flex-start;
            gap: 0.8rem;
            color: var(--light);
            line-height: 1.6;
            opacity: 1;
        }

        .objectives-list li i {
            color: var(--secondary);
            margin-top: 0.3rem;
        }

        /* 课程大纲 */
        .course-syllabus h3 {
            color: var(--secondary);
            font-size: 1.5rem;
            margin-bottom: 1.5rem;
        }

        .syllabus-section {
            margin-bottom: 1.5rem;
            border: 1px solid rgba(45, 212, 191, 0.25);
            border-radius: 10px;
            overflow: hidden;
        }

        .section-header {
            padding: 1rem 1.5rem;
            background: rgba(45, 212, 191, 0.1);
            display: flex;
            justify-content: space-between;
            align-items: center;
            cursor: pointer;
        }

        .section-header h4 {
            color: var(--secondary);
            font-size: 1.1rem;
            display: flex;
            align-items: center;
            gap: 0.8rem;
        }

        .section-header .section-meta {
            color: var(--light);
            font-size: 0.9rem;
            opacity: 0.9;
        }

        .section-content {
            padding: 0;
            max-height: 0;
            overflow: hidden;
            transition: all 0.3s ease;
        }

        .section-content.expanded {
            padding: 1rem 1.5rem;
            max-height: 1000px;
        }

        .lesson-item {
            padding: 0.8rem 0;
            border-bottom: 1px solid rgba(45, 212, 191, 0.2);
            display: flex;
            align-items: center;
            gap: 1rem;
        }

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

        .lesson-icon {
            color: var(--secondary);
            width: 20px;
            text-align: center;
        }

        .lesson-title {
            flex: 1;
            color: var(--light);
            font-size: 0.95rem;
            opacity: 1;
        }

        .lesson-duration {
            color: #a5b4fc; /* 时长文字更亮 */
            font-size: 0.85rem;
        }

        .lesson-free {
            background: rgba(45, 212, 191, 0.2);
            color: var(--secondary);
            padding: 0.2rem 0.6rem;
            border-radius: 4px;
            font-size: 0.8rem;
            border: 1px solid rgba(45, 212, 191, 0.3);
        }

        /* 讲师信息 */
        .instructor-info h3 {
            color: var(--secondary);
            font-size: 1.5rem;
            margin-bottom: 1.5rem;
        }

        .instructor-card {
            display: flex;
            gap: 1.5rem;
            padding: 1.5rem;
            background: rgba(30, 41, 59, 0.7);
            border-radius: 10px;
            border: 1px solid rgba(45, 212, 191, 0.25);
        }

        .instructor-avatar {
            width: 100px;
            height: 100px;
            border-radius: 50%;
            overflow: hidden;
            border: 2px solid var(--secondary);
            box-shadow: 0 0 15px rgba(45, 212, 191, 0.4);
        }

        .instructor-avatar img {
            width: 100%;
            height: 100%;
            object-fit: cover;
        }

        .instructor-details h4 {
            color: var(--secondary);
            font-size: 1.3rem;
            margin-bottom: 0.5rem;
        }

        .instructor-title {
            color: var(--light);
            margin-bottom: 1rem;
            font-size: 0.95rem;
            opacity: 1;
        }

        .instructor-bio {
            color: var(--light);
            line-height: 1.6;
            font-size: 0.95rem;
            margin-bottom: 1rem;
            opacity: 1;
        }

        .instructor-stats {
            display: flex;
            gap: 1.5rem;
            color: var(--light);
            font-size: 0.9rem;
        }

        .stat-item {
            display: flex;
            flex-direction: column;
        }

        .stat-value {
            color: var(--secondary);
            font-weight: 700;
            font-size: 1.1rem;
        }

        /* 侧边栏 */
        .course-sidebar {
            display: flex;
            flex-direction: column;
            gap: 1.5rem;
            position: sticky;
            top: 100px;
            height: fit-content;
        }

        /* 课程信息卡片 */
        .info-card {
            background: rgba(30, 41, 59, 0.8);
            border-radius: 15px;
            padding: 1.5rem;
            border: 1px solid rgba(45, 212, 191, 0.25);
            backdrop-filter: blur(10px);
        }

        .info-card h3 {
            color: var(--secondary);
            font-size: 1.2rem;
            margin-bottom: 1rem;
            padding-bottom: 0.8rem;
            border-bottom: 1px solid rgba(45, 212, 191, 0.25);
        }

        .info-list {
            list-style: none;
        }

        .info-item {
            display: flex;
            padding: 0.8rem 0;
            border-bottom: 1px solid rgba(45, 212, 191, 0.2);
        }

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

        .info-label {
            width: 40%;
            color: #cbd5e1; /* 标签文字更亮 */
            font-size: 0.95rem;
        }

        .info-value {
            width: 60%;
            color: var(--light);
            font-size: 0.95rem;
            opacity: 1;
        }

        /* 常见问题 */
        .faq-card {
            background: rgba(30, 41, 59, 0.8);
            border-radius: 15px;
            padding: 1.5rem;
            border: 1px solid rgba(45, 212, 191, 0.25);
            backdrop-filter: blur(10px);
        }

        .faq-card h3 {
            color: var(--secondary);
            font-size: 1.2rem;
            margin-bottom: 1rem;
            padding-bottom: 0.8rem;
            border-bottom: 1px solid rgba(45, 212, 191, 0.25);
        }

        .faq-item {
            margin-bottom: 1rem;
        }

        .faq-question {
            padding: 0.8rem 0;
            font-weight: 600;
            color: var(--secondary);
            cursor: pointer;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

        .faq-answer {
            padding: 0.8rem 0;
            color: var(--light);
            font-size: 0.95rem;
            line-height: 1.6;
            display: none;
            opacity: 1;
        }

        .faq-answer.show {
            display: block;
        }

        /* 页脚 */
        footer {
            background-color: var(--dark);
            padding: 3rem 5% 1.5rem;
            border-top: 1px solid rgba(45, 212, 191, 0.3);
            margin-top: 3rem;
        }

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

        .footer-col h3 {
            color: var(--secondary);
            margin-bottom: 1rem;
            font-size: 1.2rem;
            position: relative;
            padding-bottom: 0.5rem;
        }

        .footer-col h3::after {
            content: '';
            position: absolute;
            width: 30px;
            height: 2px;
            background: var(--secondary);
            bottom: 0;
            left: 0;
        }

        .footer-col p {
            color: var(--light);
            line-height: 1.6;
            opacity: 1;
            font-size: 0.95rem;
        }

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

        .footer-col ul li {
            margin-bottom: 0.8rem;
        }

        .footer-col ul li a {
            color: var(--light);
            text-decoration: none;
            transition: all 0.3s ease;
            font-size: 0.95rem;
            opacity: 1;
        }

        .footer-col ul li a:hover {
            color: var(--secondary);
            padding-left: 0.5rem;
            opacity: 1;
        }

        .copyright {
            text-align: center;
            padding-top: 1.5rem;
            margin-top: 1.5rem;
            border-top: 1px solid rgba(45, 212, 191, 0.2);
            color: var(--light);
            font-size: 0.9rem;
            opacity: 1;
        }

        /* 响应式设计 */
        @media (max-width: 1200px) {
            .course-detail-container {
                grid-template-columns: 65% 35%;
            }
            .video-container {
                height: 350px;
            }
        }

        @media (max-width: 992px) {
            .course-detail-container {
                grid-template-columns: 1fr;
            }
            .course-sidebar {
                position: static;
            }
            .video-container {
                height: 300px;
            }
            .course-features {
                grid-template-columns: 1fr;
            }
        }

        @media (max-width: 768px) {
            .nav-links {
                display: none;
            }
            .course-title {
                font-size: 1.8rem;
            }
            .tab-btn {
                padding: 1rem;
                font-size: 0.9rem;
            }
            .tabs-content {
                padding: 1.5rem 1rem;
            }
            .video-container {
                height: 250px;
            }
            .instructor-card {
                flex-direction: column;
                align-items: center;
                text-align: center;
            }
            .instructor-stats {
                justify-content: center;
            }
        }

        @media (max-width: 576px) {
            .course-header, .course-video, .course-tabs {
                padding: 1.5rem 1rem;
            }
            .course-meta-header {
                gap: 1rem;
            }
            .info-card, .faq-card {
                padding: 1rem;
            }
        }