/* 基础重置 */
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            line-height: 1.6;
            color: #333;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            min-height: 100vh;
            overflow-x: hidden;
        }
        
        /* 加载动画样式 - 现代简约设计 */
        .loader-container {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: linear-gradient(135deg, #1a1a2e, #16213e, #0f3460);
            display: flex;
            flex-direction: column;
            justify-content: center;
            align-items: center;
            z-index: 9999;
            transition: opacity 0.8s cubic-bezier(0.4, 0, 0.2, 1), visibility 0.8s cubic-bezier(0.4, 0, 0.2, 1);
        }
        
        .loader-container.hidden {
            opacity: 0;
            visibility: hidden;
        }
        
        /* 现代加载动画 */
        .mystic-loader {
            width: 140px;
            height: 140px;
            position: relative;
            margin-bottom: 30px;
            display: flex;
            justify-content: center;
            align-items: center;
        }
        
        /* 外环 */
        .mystic-loader::before {
            content: '';
            position: absolute;
            width: 100%;
            height: 100%;
            border: 3px solid rgba(138, 43, 226, 0.1);
            border-radius: 50%;
        }
        
        /* 旋转环 */
        .mystic-loader::after {
            content: '';
            position: absolute;
            width: 100%;
            height: 100%;
            border: 3px solid transparent;
            border-top: 3px solid #8a2be2;
            border-right: 3px solid #8a2be2;
            border-radius: 50%;
            animation: spin 1.5s linear infinite;
        }
        
        /* 核心元素 */
        .core {
            position: relative;
            width: 50px;
            height: 50px;
            background: linear-gradient(45deg, #8a2be2, #9370db);
            border-radius: 50%;
            animation: pulse 2s ease-in-out infinite;
            box-shadow: 0 0 30px rgba(138, 43, 226, 0.7);
        }
        
        /* 核心发光效果 */
        .core::before {
            content: '';
            position: absolute;
            top: -15px;
            left: -15px;
            right: -15px;
            bottom: -15px;
            background: linear-gradient(45deg, #9370db, transparent);
            border-radius: 50%;
            animation: glow 2s ease-in-out infinite;
            opacity: 0.7;
        }
        
        /* 粒子效果 - 简化为线条 */
        .particles {
            position: absolute;
            width: 100%;
            height: 100%;
        }
        
        .particle {
            position: absolute;
            width: 1px;
            height: 20px;
            background: linear-gradient(to bottom, #8a2be2, transparent);
            top: 50%;
            left: 50%;
            transform-origin: bottom;
            opacity: 0;
            animation: radiate 3s ease-in-out infinite;
        }
        
        /* 8个射线状粒子 */
        .particle:nth-child(1) { --rotate: 0deg; animation-delay: 0s; }
        .particle:nth-child(2) { --rotate: 45deg; animation-delay: 0.3s; }
        .particle:nth-child(3) { --rotate: 90deg; animation-delay: 0.6s; }
        .particle:nth-child(4) { --rotate: 135deg; animation-delay: 0.9s; }
        .particle:nth-child(5) { --rotate: 180deg; animation-delay: 1.2s; }
        .particle:nth-child(6) { --rotate: 225deg; animation-delay: 1.5s; }
        .particle:nth-child(7) { --rotate: 270deg; animation-delay: 1.8s; }
        .particle:nth-child(8) { --rotate: 315deg; animation-delay: 2.1s; }
        
        /* 加载文字 */
        .loader-text {
            color: #e0e0e0;
            font-size: 24px;
            font-weight: 500;
            letter-spacing: 3px;
            margin-top: 30px;
            animation: textGlow 2s ease-in-out infinite alternate;
            text-shadow: 0 0 10px rgba(138, 43, 226, 0.5);
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        }
        
        /* 动画定义 */
        @keyframes spin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }
        
        @keyframes pulse {
            0% { transform: scale(0.9); opacity: 0.8; }
            50% { transform: scale(1.1); opacity: 1; }
            100% { transform: scale(0.9); opacity: 0.8; }
        }
        
        @keyframes radiate {
            0% {
                transform: translate(-50%, -50%) rotate(var(--rotate)) scaleY(0);
                opacity: 0;
            }
            10% {
                transform: translate(-50%, -50%) rotate(var(--rotate)) scaleY(1);
                opacity: 1;
            }
            90% {
                transform: translate(-50%, -50%) rotate(var(--rotate)) scaleY(1);
                opacity: 1;
            }
            100% {
                transform: translate(-50%, -50%) rotate(var(--rotate)) scaleY(0);
                opacity: 0;
            }
        }
        
        @keyframes textGlow {
            from {
                text-shadow: 0 0 10px rgba(138, 43, 226, 0.5), 
                             0 0 20px rgba(138, 43, 226, 0.3);
            }
            to {
                text-shadow: 0 0 15px rgba(138, 43, 226, 0.8), 
                             0 0 30px rgba(138, 43, 226, 0.5),
                             0 0 40px rgba(138, 43, 226, 0.3);
            }
        }
        
        /* 核心发光动画 */
        @keyframes glow {
            0% {
                transform: scale(0.9);
                opacity: 0.5;
            }
            50% {
                transform: scale(1.1);
                opacity: 0.8;
            }
            100% {
                transform: scale(0.9);
                opacity: 0.5;
            }
        }
        
        /* 主容器样式 */
        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 20px;
            opacity: 0;
            transform: translateY(20px);
            transition: opacity 0.8s ease, transform 0.8s ease;
        }
        
        .container.visible {
            opacity: 1;
            transform: translateY(0);
        }
        
        /* 页面头部 */
        .header {
            background: rgba(255, 255, 255, 0.95);
            border-radius: 20px;
            padding: 30px;
            text-align: center;
            margin-bottom: 30px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
            backdrop-filter: blur(10px);
            position: relative;
            overflow: hidden;
        }
        
        .header::before {
            content: '';
            position: absolute;
            top: -50%;
            left: -50%;
            width: 200%;
            height: 200%;
            background: linear-gradient(45deg, transparent 48%, rgba(102, 126, 234, 0.1) 49%, rgba(102, 126, 234, 0.1) 51%, transparent 52%);
            background-size: 20px 20px;
            animation: gridMove 20s linear infinite;
            z-index: 0;
        }
        
        @keyframes gridMove {
            0% { transform: translate(0, 0); }
            100% { transform: translate(40px, 40px); }
        }
        
        .header-content {
            position: relative;
            z-index: 1;
        }
        
        .header h1 {
            color: #667eea;
            font-size: 2.5rem;
            margin-bottom: 15px;
            font-weight: 700;
            text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.1);
            animation: fadeInUp 1s ease;
        }
        
        @keyframes fadeInUp {
            from {
                opacity: 0;
                transform: translateY(20px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }
        
        .header p {
            color: #666;
            font-size: 1.1rem;
            max-width: 800px;
            margin: 0 auto;
            animation: fadeInUp 1s ease 0.2s both;
        }
        
        /* 课程网格布局 */
        .grade-grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
            gap: 10px;
            margin-top: 15px;
        }
        
        /* 年级卡片样式 */
        .grade-card {
            background: rgba(255, 255, 255, 0.95);
            border-radius: 15px;
            overflow: hidden;
            box-shadow: 0 8px 25px rgba(0, 0, 0, 0.1);
            transition: transform 0.3s ease, box-shadow 0.3s ease;
            backdrop-filter: blur(10px);
            position: relative;
        }
        
        .grade-card:hover {
            transform: translateY(-10px);
            box-shadow: 0 15px 35px rgba(0, 0, 0, 0.15);
        }
        
        .grade-card::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 5px;
            background: linear-gradient(90deg, #667eea, #764ba2);
        }
        
        /* 年级标题栏 */
        .grade-header {
            display: flex;
            align-items: center;
            padding: 18px;
            cursor: pointer;
            transition: background-color 0.3s ease;
        }
        
        .grade-header:hover {
            background-color: rgba(102, 126, 234, 0.05);
        }
        
        .grade-icon {
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            margin-right: 15px;
            font-size: 1.2rem;
            box-shadow: 0 4px 10px rgba(102, 126, 234, 0.3);
        }
        
        .grade-title {
            flex: 1;
            font-size: 1.2rem;
            font-weight: 600;
            color: #333;
        }
        
        .toggle-icon {
            color: #667eea;
            font-size: 1.1rem;
            transition: transform 0.3s ease;
        }
        
        .grade-card.expanded .toggle-icon {
            transform: rotate(90deg);
        }
        
        /* 单元列表 */
        .units-container {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.4s ease;
            background: rgba(248, 249, 250, 0.8);
        }
        
        .grade-card.expanded .units-container {
            max-height: 800px;
        }
        
        .unit-list {
            list-style: none;
            padding: 10px 0;
        }
        
        .unit-item {
            position: relative;
            overflow: hidden;
        }
        
        .unit-link {
            display: flex;
            align-items: center;
            padding: 15px 20px 15px 75px;
            color: #495057;
            text-decoration: none;
            transition: all 0.3s ease;
            position: relative;
            z-index: 1;
        }
        
        .unit-link::before {
            content: '';
            position: absolute;
            left: 0;
            top: 0;
            width: 0;
            height: 100%;
            background: linear-gradient(90deg, rgba(102, 126, 234, 0.1), transparent);
            transition: width 0.3s ease;
            z-index: -1;
        }
        
        .unit-link:hover {
            color: #667eea;
            padding-left: 85px;
        }
        
        .unit-link:hover::before {
            width: 100%;
        }
        
        .unit-link i {
            position: absolute;
            left: 20px;
            color: #667eea;
            font-size: 1.2rem;
            transition: transform 0.3s ease;
        }
        
        .unit-link:hover i {
            transform: scale(1.2) rotate(10deg);
        }
        
        /* 年级卡片角标 */
        .grade-badge {
            position: absolute;
            top: 15px;
            right: 15px;
            background: linear-gradient(135deg, #667eea, #764ba2);
            color: white;
            padding: 5px 10px;
            border-radius: 20px;
            font-size: 0.8rem;
            font-weight: 600;
            box-shadow: 0 4px 10px rgba(102, 126, 234, 0.3);
        }
        
        /* 悬浮装饰元素 */
        .floating-elements {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            pointer-events: none;
            z-index: -1;
        }
        
        .floating-element {
            position: absolute;
            border-radius: 50%;
            background: rgba(255, 255, 255, 0.1);
            animation: float 15s infinite ease-in-out;
        }
        
        .floating-1 {
            width: 150px;
            height: 150px;
            top: 10%;
            left: 5%;
            animation-delay: 0s;
        }
        
        .floating-2 {
            width: 100px;
            height: 100px;
            top: 60%;
            left: 80%;
            animation-delay: -5s;
        }
        
        .floating-3 {
            width: 80px;
            height: 80px;
            top: 30%;
            left: 90%;
            animation-delay: -10s;
        }
        
        .floating-4 {
            width: 120px;
            height: 120px;
            top: 80%;
            left: 10%;
            animation-delay: -8s;
        }
        
        @keyframes float {
            0%, 100% {
                transform: translate(0, 0) rotate(0deg);
            }
            25% {
                transform: translate(30px, -30px) rotate(90deg);
            }
            50% {
                transform: translate(0, -50px) rotate(180deg);
            }
            75% {
                transform: translate(-30px, -30px) rotate(270deg);
            }
        }
        
        /* 响应式设计 */
        @media (max-width: 768px) {
            .grade-grid {
                grid-template-columns: 1fr;
            }
            
            .header h1 {
                font-size: 2rem;
            }
            
            .container {
                padding: 15px;
            }
            
            .grade-card {
                margin-bottom: 10px;
            }
        }
        
        @media (max-width: 480px) {
            .header {
                padding: 20px 15px;
            }
              .grade-card {
                margin-bottom: 5px;
            }
            .header h1 {
                font-size: 1.8rem;
            }
            
            .grade-header {
                padding: 15px;
            }
            
            .unit-link {
                padding: 12px 15px 12px 65px;
            }
            
            .unit-link:hover {
                padding-left: 75px;
            }
        }