/* ============================================================
   E+编程在线学习平台 - 样式表（完整版）
   包含：粒子背景、登录页面、六大课程卡片（2行×3列）、
         课程网格、班级管理、作业批改优化（同一行）、
         文档预览区与视频预览区统一高度120px
   ============================================================ */

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

body {
    font-family: 'Microsoft YaHei', -apple-system, BlinkMacSystemFont,
                 'Segoe UI', Arial, sans-serif;
    min-height: 100vh;
    background: #0a0e27;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ==================== 登录页面 ==================== */
#authPage {
    display: flex;
    min-height: 100vh;
    position: relative;
    overflow: hidden;
    background: radial-gradient(ellipse at center, #1a1a3e 0%, #0a0e27 70%);
}

.particle-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1;
}

.auth-left-floating {
    position: absolute;
    left: 8%;
    top: 50%;
    transform: translateY(-50%);
    z-index: 2;
    animation: floatLeft 6s ease-in-out infinite;
}
@keyframes floatLeft {
    0%, 100% { transform: translateY(-50%) translateX(0); }
    50% { transform: translateY(-50%) translateX(-12px); }
}
.auth-right-floating {
    position: absolute;
    right: 8%;
    top: 50%;
    transform: translateY(-50%);
    z-index: 2;
    animation: floatRight 6s ease-in-out infinite;
}
@keyframes floatRight {
    0%, 100% { transform: translateY(-50%) translateX(0); }
    50% { transform: translateY(-50%) translateX(12px); }
}
.floating-title {
    font-size: 20px;
    font-weight: 700;
    color: #fff;
    text-shadow: 0 0 20px rgba(100, 180, 255, 0.6);
    margin-bottom: 24px;
    text-align: center;
}
.floating-courses,
.floating-features {
    display: flex;
    flex-direction: column;
    gap: 30px;
}
.floating-course-item,
.floating-feature-item {
    display: flex;
    align-items: center;
    gap: 20px;
    background: rgba(255, 255, 255, 0.06);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.12);
    border-radius: 14px;
    padding: 16px 20px;
    transition: all 0.4s;
    cursor: default;
    width: 260px;
}
.floating-course-item:hover,
.floating-feature-item:hover {
    background: rgba(255, 255, 255, 0.12);
    transform: translateX(8px);
    border-color: rgba(100, 180, 255, 0.4);
    box-shadow: 0 8px 25px rgba(0, 100, 255, 0.15);
}
.floating-course-icon,
.feature-icon {
    font-size: 36px;
    flex-shrink: 0;
    transition: transform 0.4s;
}
.floating-course-item:hover .floating-course-icon {
    transform: scale(1.2) rotate(-10deg);
}
.floating-feature-item:hover .feature-icon {
    transform: scale(1.2);
}
.floating-course-info,
.feature-info {
    display: flex;
    flex-direction: column;
    gap: 4px;
}
.floating-course-name,
.feature-name {
    font-size: 16px;
    font-weight: 700;
    color: #fff;
}
.floating-course-desc,
.feature-desc {
    font-size: 11px;
    color: rgba(255, 255, 255, 0.6);
}
.floating-course-item.course-scratch:hover { border-color: rgba(255, 154, 60, 0.5); }
.floating-course-item.course-python:hover { border-color: rgba(55, 118, 171, 0.5); }
.floating-course-item.course-cpp:hover { border-color: rgba(118, 75, 162, 0.5); }
.floating-course-item.course-hardware:hover { border-color: rgba(108, 117, 125, 0.5); }

.auth-overlay {
    position: relative;
    z-index: 3;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
}
.auth-container {
    max-width: 360px;
    width: 90%;
    background: rgba(255, 255, 255, 0.95);
    border-radius: 16px;
    padding: 28px 24px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}
.platform-title {
    text-align: center;
    margin-bottom: 6px;
    font-weight: bold;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 2px;
}
.title-e {
    font-size: 48px;
    font-weight: 900;
    color: #0aed83;
    text-shadow: 0 0 10px rgba(125, 238, 49, 0.5), 0 0 20px rgba(152, 255, 34, 0.3);
    line-height: 1;
}
.title-plus {
    font-size: 34px;
    font-weight: 900;
    color: #667eea;
    text-shadow: 0 0 10px rgba(102, 126, 234, 0.5), 0 0 20px rgba(102, 126, 234, 0.3);
    line-height: 1;
    margin: 0 1px;
}
.title-text {
    font-size: 30px;
    color: #333;
    font-weight: 700;
    line-height: 1;
    margin-left: 2px;
}
.platform-subtitle {
    text-align: center;
    color: #888;
    margin-bottom: 18px;
    font-size: 14px;
    margin-top: 2px;
}
.auth-tabs {
    display: flex;
    margin-bottom: 18px;
    border-bottom: 2px solid #eee;
}
.auth-tab {
    flex: 1;
    padding: 8px;
    border: none;
    background: none;
    cursor: pointer;
    font-size: 14px;
    color: #999;
    transition: all 0.3s;
    position: relative;
}
.auth-tab.active {
    color: #667eea;
    font-weight: bold;
}
.auth-tab.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 100%;
    height: 2px;
    background: #667eea;
}
.auth-form {
    display: flex;
    flex-direction: column;
    gap: 16px;
}
.form-group {
    display: flex;
    flex-direction: column;
    gap: 5px;
}
.form-group label {
    font-size: 13px;
    color: #444;
    font-weight: 600;
}
.form-group input,
.form-group select,
.form-group textarea {
    padding: 10px 12px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    font-size: 14px;
    transition: all 0.3s;
    font-family: inherit;
}
.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}
.form-row {
    display: flex;
    gap: 12px;
}
.flex-1 {
    flex: 1;
}
.auth-footer {
    text-align: center;
    margin-top: 24px;
    padding: 12px 0 8px;
    font-size: 10px;
    color: #888;
    border-top: 1px solid #eee;
}

/* 按钮样式 */
.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 600;
    transition: all 0.3s;
    box-shadow: 0 4px 12px rgba(230, 231, 234, 0.897);
}
.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 18px rgba(238, 239, 243, 0.868);
}
.btn-secondary {
    background: #dd8706db;
    color: #fcf9f9;
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 600;
    transition: all 0.3s;
    box-shadow: 0 3px 10px rgba(99, 101, 103, 0.766);
}
.btn-secondary:hover {
    transform: translateY(-2px);
    background: #4c4e4e;
}
.btn-delete {
    background: #dc3545;
    color: white;
    border: none;
    padding: 5px 10px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 11px;
    transition: all 0.3s;
}
.btn-delete:hover { background: #c82333; }
.btn-edit {
    background: #28a745;
    color: white;
    border: none;
    padding: 5px 10px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 11px;
}
.btn-edit:hover { background: #218838; }
.btn-add {
    background: #17a2b8;
    color: white;
    border: none;
    padding: 5px 10px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 11px;
}
.btn-add:hover { background: #138496; }
.btn-warning {
    background: #ffc107;
    color: #333;
    border: none;
    padding: 5px 10px;
    border-radius: 5px;
    cursor: pointer;
    font-size: 11px;
}
.btn-warning:hover { background: #e0a800; }
.btn-small {
    padding: 5px 10px;
    font-size: 11px;
    margin-left: 6px;
}
.btn-add-teacher {
    background: linear-gradient(135deg, #4a90d9 0%, #357abd 100%);
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 600;
}
.btn-add-teacher:hover {
    background: linear-gradient(135deg, #5a9fe5 0%, #4a8dc9 100%);
    transform: translateY(-2px);
}
.btn-add-student {
    background: linear-gradient(135deg, #27ae60 0%, #1e8449 100%);
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 600;
}
.btn-add-student:hover {
    background: linear-gradient(135deg, #2ecc71 0%, #27ae60 100%);
    transform: translateY(-2px);
}
.btn-add-teacher-small {
    background: linear-gradient(135deg, #4a90d9 0%, #357abd 100%);
    color: white;
    padding: 8px 16px;
    border-radius: 8px;
    font-size: 12px;
    font-weight: 600;
}
.btn-add-student-small {
    background: linear-gradient(135deg, #27ae60 0%, #1e8449 100%);
    color: white;
    padding: 8px 16px;
    border-radius: 8px;
    font-size: 12px;
    font-weight: 600;
}
.btn-submission {
    background: #17a2b8;
    color: white;
    border: none;
    padding: 4px 8px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 10px;
    margin-left: 5px;
}
.btn-submission:hover { background: #138496; }
.course-score {
    font-size: 10px;
    color: #28a745;
    font-weight: bold;
    margin: 4px 0;
}

/* 头部导航 */
.header {
    background: rgba(255, 255, 255, 0.97);
    padding: 12px 25px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 15px rgba(0, 0, 0, 0.08);
    margin-bottom: 15px;
    border-radius: 12px;
}
.header-left h1 .title-e { font-size: 36px; }
.header-left h1 .title-plus { font-size: 28px; }
.header-left h1 .title-text { font-size: 24px; }
.header-nav {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}
.nav-dropdown {
    position: relative;
    display: inline-block;
}
.nav-dropdown-btn {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    padding: 8px 14px;
    border-radius: 8px;
    cursor: pointer;
    font-size: 13px;
    font-weight: 500;
}
.nav-dropdown-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
}
.nav-dropdown-content {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background: white;
    min-width: 200px;
    border-radius: 8px;
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
    z-index: 100;
    overflow: hidden;
    margin-top: 4px;
}
.nav-dropdown.active .nav-dropdown-content { display: block; }
.nav-dropdown-content a {
    display: block;
    padding: 10px 16px;
    color: #333;
    text-decoration: none;
    font-size: 13px;
    border-bottom: 1px solid #f0f0f0;
}
.nav-dropdown-content a:hover {
    background: #f8f9ff;
    color: #667eea;
}
#welcomeUser {
    color: #555;
    font-size: 12px;
    margin: 0 6px;
}
.sub-header {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    margin-bottom: 15px;
    flex-wrap: wrap;
}

/* 主内容区域 */
.main-content { padding-bottom: 30px; }
.content-area {
    background: rgba(255, 255, 255, 0.97);
    border-radius: 12px;
    padding: 25px;
    box-shadow: 0 2px 15px rgba(0, 0, 0, 0.08);
    min-height: 500px;
}
.breadcrumb {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 10px 14px;
    background: #f5f6fa;
    border-radius: 8px;
    margin-bottom: 18px;
    font-size: 13px;
    flex-wrap: wrap;
}
.breadcrumb a {
    color: #667eea;
    text-decoration: none;
    cursor: pointer;
    font-weight: 500;
}
.breadcrumb a:hover { text-decoration: underline; }
.breadcrumb .separator { color: #ccc; }
.breadcrumb .current { color: #333; font-weight: 600; }

/* 课程分类卡片（3列） */
.category-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
    max-width: 1000px;
    margin: 0 auto;
    align-items: center;
    overflow-x: auto;
}
.category-card {
    background: white;
    border: 3px solid #e8e8e8;
    border-radius: 18px;
    padding: 30px 20px;
    cursor: pointer;
    transition: all 0.3s;
    text-align: center;
    min-height: 280px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
}
.category-card:hover {
    transform: translateY(-6px);
    box-shadow: 0 12px 30px rgba(0, 0, 0, 0.1);
}
.category-card .card-icon {
    width: 120px;
    height: 120px;
    border-radius: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 16px;
    font-size: 36px;
    font-weight: 900;
    color: white;
    transition: all 0.3s;
}
.category-card:hover .card-icon {
    transform: scale(1.1) rotate(-3deg);
}
.category-card.graphical { border-color: #f7a440; }
.category-card.graphical .card-icon {
    background: linear-gradient(135deg, #ff9a3c 0%, #4caf50 100%);
    border: 4px solid rgba(192, 233, 8, 0.535);
    box-shadow: inset 0 0 0 6px rgba(255, 255, 255, 0.2), 0 4px 0 #388e3c, 0 6px 0 #2e7d32;
    border-radius: 20px 20px 20px 8px;
    font-family: 'Comic Sans MS', cursive;
    font-size: 28px;
    text-shadow: 2px 2px 0 rgba(0, 0, 0, 0.2);
    color: #e6cd0e;
}
.category-card.python { border-color: #3776ab; }
.category-card.python .card-icon {
    background: linear-gradient(135deg, #ff9a3c 0%, #3776ab 100%);
    font-size: 60px;
}
.category-card.cpp { border-color: #764ba2; }
.category-card.cpp .card-icon {
    background: linear-gradient(135deg, #ff9a3c 0%, #764ba2 100%);
    font-family: 'Consolas', monospace;
    font-size: 42px;
    letter-spacing: -2px;
    border: 4px solid rgba(255, 255, 255, 0.3);
}
.category-card.hardware { border-color: #888; }
.category-card.hardware .card-icon {
    background: linear-gradient(135deg, #ff9a3c 0%, #6c757d 100%);
    font-size: 60px;
}
.category-card.math { border-color: #f39c12; }
.category-card.math .card-icon {
    background: linear-gradient(135deg, #f1c40f 0%, #e67e22 100%);
    font-size: 48px;
}
.category-card.english { border-color: #3498db; }
.category-card.english .card-icon {
    background: linear-gradient(135deg, #3498db 0%, #9b59b6 100%);
    font-size: 24px;
    font-weight: bold;
    font-family: 'Arial', sans-serif;
}
.category-card h3 {
    font-size: 20px;
    color: #333;
    margin-bottom: 8px;
}
.category-card .card-desc {
    color: #777;
    font-size: 13px;
    line-height: 1.6;
    max-width: 250px;
    white-space: pre-line;
}

/* Level网格 */
.level-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 15px;
}
.level-folder {
    background: white;
    border: 2px solid #e8e8e8;
    border-radius: 14px;
    padding: 20px 12px;
    cursor: pointer;
    text-align: center;
    transition: all 0.3s;
}
.level-folder:hover {
    border-color: #667eea;
    transform: translateY(-3px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.12);
}
.level-folder .folder-icon { font-size: 48px; margin-bottom: 10px; }
.level-folder .level-number {
    font-size: 16px;
    font-weight: 700;
    color: #667eea;
    margin-bottom: 4px;
}
.level-folder .level-title { font-size: 13px; color: #666; }
.level-folder .course-count {
    font-size: 11px;
    color: #999;
    background: #f0f0f0;
    padding: 3px 10px;
    border-radius: 10px;
    margin-top: 6px;
}
.level-folder.no-access {
    opacity: 0.4;
    cursor: not-allowed;
}
.level-folder.no-access:hover { transform: none; }

/* 章节网格 */
.chapter-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 10px;
}
.chapter-card {
    background: white;
    border: 2px solid #e8e8e8;
    border-radius: 10px;
    padding: 16px 10px;
    cursor: pointer;
    text-align: center;
    transition: all 0.3s;
}
.chapter-card:hover {
    border-color: #764ba2;
    transform: translateY(-2px);
}
.chapter-card .chapter-icon { font-size: 28px; margin-bottom: 4px; }
.chapter-card .chapter-number {
    font-size: 11px;
    color: #764ba2;
    font-weight: 600;
}
.chapter-card .chapter-title { font-size: 12px; color: #333; }
.chapter-card .chapter-course-count {
    font-size: 10px;
    color: #999;
    margin-top: 3px;
}
.chapter-card.empty {
    border-style: dashed;
    opacity: 0.35;
    cursor: default;
}

/* 课程网格 - 统一预览区高度为120px */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}
.course-card {
    background: white;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
    border: 1px solid #f0f0f0;
}
.course-card:hover { transform: translateY(-3px); }
.course-card video {
    width: 100%;
    height: 120px;
    object-fit: cover;
    background: #000;
}
.course-info { padding: 10px; }
.course-info h3 {
    font-size: 11px;
    color: #333;
    margin-bottom: 3px;
}
/* 已删除 .course-filename 样式，不再显示 */
.course-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 5px;
    border-top: 1px solid #f0f0f0;
    font-size: 10px;
    color: #999;
}
.document-preview {
    height: 120px;
    background: linear-gradient(135deg, #f8f9ff, #f0f2ff);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 6px;
}
.document-icon { font-size: 30px; }
.document-link {
    color: #667eea;
    text-decoration: none;
    font-size: 14px;
}
.no-content {
    height: 120px;
    background: #f8f9fa;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #bbb;
    font-size: 11px;
}
.course-filter {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
    margin-bottom: 15px;
}
.filter-btn {
    padding: 7px 14px;
    border: 2px solid #667eea;
    background: white;
    color: #667eea;
    border-radius: 16px;
    cursor: pointer;
    font-size: 12px;
}
.filter-btn.active,
.filter-btn:hover {
    background: #667eea;
    color: white;
}
.pagination {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 4px;
    margin-top: 20px;
    padding-top: 15px;
    border-top: 1px solid #eee;
}
.pagination button {
    padding: 6px 10px;
    border: 1px solid #ddd;
    background: white;
    border-radius: 5px;
    cursor: pointer;
    font-size: 11px;
}
.pagination button:hover:not(:disabled) {
    background: #667eea;
    color: white;
}
.pagination button.active {
    background: #667eea;
    color: white;
}
.pagination button:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}
.pagination .page-info {
    font-size: 11px;
    color: #888;
    padding: 0 5px;
}
.class-tabs {
    display: flex;
    gap: 6px;
    margin-bottom: 15px;
}
.class-tab {
    padding: 7px 14px;
    border: 2px solid #764ba2;
    background: white;
    color: #764ba2;
    border-radius: 16px;
    cursor: pointer;
    font-size: 12px;
}
.class-tab.active,
.class-tab:hover {
    background: #764ba2;
    color: white;
}
.table-responsive { overflow-x: auto; margin-top: 8px; }
.manage-table {
    width: 100%;
    border-collapse: collapse;
    background: white;
    font-size: 12px;
}
.manage-table thead {
    background: #667eea;
    color: white;
}
.manage-table th,
.manage-table td {
    padding: 8px 10px;
    text-align: left;
    border-bottom: 1px solid #f0f0f0;
}
.manage-table tbody tr:hover { background: #fafbff; }
.form-card {
    margin-top: 15px;
    padding: 15px;
    background: #f9fafb;
    border-radius: 8px;
    border: 1px solid #e8e8e8;
}
.permission-tag {
    display: inline-block;
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 10px;
}
.permission-tag.active {
    background: #d4edda;
    color: #155724;
}
.permission-tag.inactive {
    background: #f8d7da;
    color: #721c24;
}
.multi-select-container { position: relative; }
.multi-select-display {
    padding: 8px 12px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    cursor: pointer;
    min-height: 38px;
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
    background: white;
}
.multi-select-dropdown {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: white;
    border: 2px solid #667eea;
    border-radius: 8px;
    max-height: 200px;
    overflow-y: auto;
    padding: 8px;
    z-index: 50;
}
.multi-select-container.active .multi-select-dropdown { display: block; }
.multi-select-tag {
    display: inline-block;
    padding: 2px 8px;
    background: #667eea;
    color: white;
    border-radius: 12px;
    font-size: 11px;
}
.submissions-list { max-height: 400px; overflow-y: auto; }
.submission-item {
    border: 1px solid #eee;
    padding: 10px;
    margin-bottom: 8px;
    border-radius: 6px;
    background: #f9f9f9;
}
.submission-info { font-size: 12px; }
.submission-score {
    background: #d4edda;
    padding: 2px 6px;
    border-radius: 10px;
    margin-left: 8px;
}
.submission-feedback {
    font-size: 11px;
    color: #666;
    margin-top: 4px;
}
.score-form {
    display: flex;
    flex-wrap: nowrap;
    align-items: center;
    gap: 8px;
}
.score-form input,
.score-form button {
    white-space: nowrap;
}
.no-submissions {
    text-align: center;
    color: #999;
    padding: 20px;
}
.student-select-list {
    max-height: 300px;
    overflow-y: auto;
    border: 1px solid #e0e0e0;
    border-radius: 8px;
    padding: 8px;
}
.student-select-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 6px 8px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 13px;
}
.student-select-item:hover { background: #f0f0ff; }
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    backdrop-filter: blur(2px);
}
.modal-content {
    background: white;
    padding: 25px;
    border-radius: 12px;
    max-width: 600px;
    width: 90%;
    position: relative;
    max-height: 90vh;
    overflow-y: auto;
}
.close {
    position: absolute;
    right: 15px;
    top: 10px;
    font-size: 24px;
    cursor: pointer;
    color: #bbb;
}
.close:hover { color: #333; }

/* 响应式设计 */
@media (max-width: 1200px) {
    .level-grid, .chapter-grid, .courses-grid { grid-template-columns: repeat(3, 1fr); }
    .auth-left-floating, .auth-right-floating { display: none; }
}
@media (max-width: 768px) {
    .header { flex-direction: column; }
    .level-grid, .chapter-grid, .courses-grid { grid-template-columns: repeat(2, 1fr); }
    .form-row { flex-direction: column; }
    .auth-left-floating, .auth-right-floating { display: none; }
}
@media (max-width: 480px) {
    .level-grid, .chapter-grid, .courses-grid { grid-template-columns: 1fr; }
}

/* ========== 课程卡片放大图标和文字 ========== */
.document-preview .document-icon {
    font-size: 60px !important;
}
.document-link {
    font-size: 20px !important;
}
.course-info h3 {
    font-size: 22px !important;
}
.course-footer small,
.course-footer button {
    font-size: 14px !important;
}
.course-score {
    font-size: 14px !important;
}
.course-card .course-info {
    padding: 15px;
}