/* 
 * AI公益课堂 - 关爱老年人
 * 主样式表
 */

/* ================= 颜色变量 ================= */
:root {
    --primary-color: #4961DC;
    --primary-dark: #3F51B5;
    --primary-light: #6A98F0;
    --secondary-color: #FF5722;
    --text-dark: #333;
    --text-medium: #666;
    --text-light: #888;
    --bg-light: #f5f7ff;
    --bg-medium: #e8eeff;
    --shadow-light: 0 5px 15px rgba(0, 0, 0, 0.05);
    --shadow-medium: 0 8px 20px rgba(0, 0, 0, 0.1);
    --shadow-dark: 0 10px 30px rgba(0, 0, 0, 0.15);
    --transition-fast: 0.3s ease;
    --transition-medium: 0.5s ease;
    --transition-slow: 0.8s ease;
    --border-radius-sm: 8px;
    --border-radius-md: 15px;
    --border-radius-lg: 30px;
}

/* ================= 基础样式 ================= */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Microsoft YaHei', sans-serif;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 70px; /* 为固定导航栏预留空间 */
}

body {
    overflow-x: hidden;
    color: var(--text-dark);
    background-color: #fff;
    line-height: 1.6;
    font-size: 16px;
}

h1, h2, h3, h4, h5, h6 {
    line-height: 1.3;
    margin-bottom: 1rem;
}

a {
    text-decoration: none;
    color: var(--primary-color);
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--primary-dark);
}

p {
    margin-bottom: 1.5rem;
}

img {
    max-width: 100%;
    height: auto;
}

section {
    min-height: 100vh;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
}

.section-title {
    position: relative;
    display: inline-block;
    margin-bottom: 2.5rem;
    color: var(--primary-dark);
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 3px;
    background: var(--primary-color);
}

/* ================= 导航栏样式 ================= */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 70px;
    background: rgba(255, 255, 255, 0.95);
    box-shadow: var(--shadow-light);
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 5%;
    z-index: 1000;
    transition: all var(--transition-fast);
}

.navbar.scrolled {
    background: rgba(255, 255, 255, 0.98);
    box-shadow: var(--shadow-medium);
    height: 60px;
}

.logo {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: var(--primary-color);
    font-weight: bold;
    font-size: 1.5rem;
}

.logo i {
    margin-right: 10px;
    font-size: 1.8rem;
    transition: transform var(--transition-fast);
}

.logo:hover i {
    transform: rotate(10deg);
}

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

.nav-links li {
    margin: 0 15px;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-dark);
    font-weight: 500;
    font-size: 1.1rem;
    transition: color var(--transition-fast);
    position: relative;
    padding: 5px 0;
}

.nav-links a:hover {
    color: var(--primary-color);
}

.nav-links a::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: 0;
    left: 0;
    background-color: var(--primary-color);
    transition: width var(--transition-fast);
}

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

.nav-links a.active {
    color: var(--primary-color);
}

.hamburger {
    display: none;
    cursor: pointer;
    background: none;
    border: none;
    color: var(--text-dark);
    font-size: 1.5rem;
    transition: color var(--transition-fast);
}

.hamburger:hover {
    color: var(--primary-color);
}

/* ================= 欢迎页样式 ================= */
#welcome {
    background: linear-gradient(135deg, var(--primary-light), var(--primary-color));
    color: white;
    position: relative;
    padding: 0;
    display: flex;
    flex-direction: column;
    padding-top: 70px; /* 为固定导航栏预留空间 */
    height: 100vh; /* 限制高度，避免超出屏幕 */
    overflow: hidden; /* 避免内容溢出 */
}

.welcome-top {
    height: 60vh;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 3rem;
    position: relative;
    z-index: 2; /* 确保内容显示在上层 */
}

.welcome-content {
    max-width: 900px;
    text-align: center;
    opacity: 0;
    transform: translateY(20px);
    animation: fadeIn 1.5s ease forwards;
}

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

h1 {
    font-size: 3.8rem;
    margin-bottom: 1.5rem;
    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
}

.welcome-subtitle {
    color: rgba(255, 255, 255, 0.9);
    font-size: 2rem;
    margin-bottom: 2rem;
    text-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
}

.welcome-gallery {
    height: 40vh;
    width: 100%;
    position: relative;
    overflow: visible; /* 允许内容溢出不被裁剪 */
    background-color: rgba(0, 0, 0, 0.2);
    position: relative;
    z-index: 1;
    padding-top: 30px; /* 为放大的图片提供更多空间 */
}

/* 添加伪元素实现平滑过渡 */
.welcome-gallery::before {
    content: '';
    position: absolute;
    top: -50px;
    left: 0;
    width: 100%;
    height: 50px;
    background: linear-gradient(to bottom, rgba(73, 97, 220, 0), rgba(0, 0, 0, 0.2));
    z-index: 3;
    pointer-events: none; /* 确保伪元素不会阻止鼠标事件 */
}

.gallery-container {
    display: flex;
    position: absolute;
    height: calc(100% - 30px); /* 减去顶部内边距的高度 */
    animation: slideGallery 25s linear infinite;
    padding: 10px 0; /* 添加内边距使元素有空间放大而不被遮挡 */
}

@keyframes slideGallery {
    0% {
        transform: translateX(0);
    }
    100% {
        transform: translateX(-50%);
    }
}

.gallery-item {
    min-width: 300px;
    height: calc(100% - 20px); /* 调整高度，为放大腾出空间 */
    margin: 0 10px;
    background-color: #fff;
    border-radius: var(--border-radius-sm);
    overflow: hidden;
    box-shadow: var(--shadow-medium);
    transition: all var(--transition-fast);
    transform-style: preserve-3d;
    perspective: 1000px;
    position: relative;
    z-index: 1;
    transform-origin: center center;
}

.gallery-item:hover {
    transform: scale(1.1);
    z-index: 10;
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.4);
}

.gallery-img {
    width: 100%;
    height: 80%;
    object-fit: cover;
    transition: all var(--transition-medium);
}

.gallery-item:hover .gallery-img {
    transform: scale(1.05);
}

.gallery-caption {
    height: 20%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-dark);
    font-weight: bold;
    padding: 0 10px;
}

.scroll-down {
    position: absolute;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 1rem;
    color: white;
    display: flex;
    flex-direction: column;
    align-items: center;
    cursor: pointer;
    animation: bounce 2s infinite;
    z-index: 20;
    padding: 10px 20px;
    border-radius: var(--border-radius-lg);
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(3px);
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.3);
    transition: all var(--transition-fast);
    width: auto; /* 确保宽度自适应内容 */
    max-width: 220px; /* 限制最大宽度 */
    text-align: center; /* 确保文本居中 */
}

/* 修复ripple效果对按钮宽度的影响 */
.scroll-down.ripple {
    position: absolute; /* 保持绝对定位 */
    width: auto; /* 保持宽度自适应 */
    max-width: 220px; /* 限制最大宽度 */
}

/* 添加波纹效果样式 */
.ripple-effect {
    position: absolute;
    border-radius: 50%;
    background-color: rgba(255, 255, 255, 0.7);
    width: 100px;
    height: 100px;
    margin-top: -50px;
    margin-left: -50px;
    animation: ripple 0.6s linear;
    transform: scale(0);
    opacity: 1;
    pointer-events: none;
}

@keyframes ripple {
    to {
        transform: scale(2.5);
        opacity: 0;
    }
}

.scroll-down:hover {
    background-color: rgba(0, 0, 0, 0.7);
    transform: translateX(-50%) translateY(-5px);
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateY(0) translateX(-50%);
    }
    40% {
        transform: translateY(-15px) translateX(-50%);
    }
    60% {
        transform: translateY(-7px) translateX(-50%);
    }
}

.scroll-down i {
    font-size: 1.5rem;
    margin-top: 0.5rem;
}

/* ================= 课程内容样式 ================= */
.course-container {
    display: flex;
    width: 100%;
    max-width: 1200px;
    margin: 2rem auto;
    gap: 2rem;
}

.course-slider {
    flex: 3;
    position: relative;
    overflow: hidden;
    height: 500px;
    border-radius: var(--border-radius-md);
    box-shadow: var(--shadow-dark);
    background: linear-gradient(135deg, var(--bg-light), var(--bg-medium));
}

.course-card {
    z-index: 0;
    top: 0;
    left: 0;
    transform: translateX(50px);
    transition: opacity var(--transition-slow), transform var(--transition-slow);
    position: absolute;
    width: 100%;
    height: 100%;
    opacity: 0;
    background-size: cover;
    background-position: center;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    padding: 3rem;
    color: white;
    overflow: hidden;
}

.course-card.active {
    z-index: 1;
    opacity: 1;
    transform: translateX(0);
}

.course-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(to top, rgba(0, 0, 0, 0.8), rgba(0, 0, 0, 0.2));
    z-index: 0;
}

.course-content {
    position: relative;
    z-index: 1;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    max-width: 90%;
}

.course-title {
    font-size: 2.5rem;
    margin-bottom: 1.5rem;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.5);
    position: relative;
}

.course-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 0;
    width: 80px;
    height: 3px;
    background: #fff;
}

.course-description {
    font-size: 1.2rem;
    line-height: 1.8;
    margin-bottom: 1.5rem;
    text-shadow: 0 1px 3px rgba(0, 0, 0, 0.5);
}

.course-button {
    padding: 0.8rem 1.5rem;
    background: white;
    color: var(--primary-color);
    border: none;
    border-radius: var(--border-radius-lg);
    font-size: 1.1rem;
    font-weight: bold;
    cursor: pointer;
    transition: all var(--transition-fast);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
    position: relative;
    overflow: hidden;
    z-index: 1;
}

.course-button::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: var(--primary-color);
    transition: all 0.4s ease;
    z-index: -1;
}

.course-button:hover {
    color: #ffffff; /* 保持文字在背景上可见 */
    transform: translateY(-3px);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
}

.course-button:hover::before {
    left: 0;
}

.slider-nav {
    position: absolute;
    bottom: 1rem;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    z-index: 5;
}

.slider-dot {
    width: 12px;
    height: 12px;
    background: rgba(255, 255, 255, 0.5);
    border-radius: 50%;
    margin: 0 0.5rem;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.slider-dot.active {
    background: #fff;
    transform: scale(1.2);
}

.course-action {
    flex: 2;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    padding: 2rem;
    background: rgba(73, 97, 220, 0.05);
    border-radius: var(--border-radius-md);
    box-shadow: var(--shadow-light);
    position: relative;
    transition: all var(--transition-fast);
}

.course-action::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border-radius: var(--border-radius-md);
    background: linear-gradient(135deg, transparent, rgba(73, 97, 220, 0.05));
    z-index: -1;
}

.course-action:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-medium);
}

.course-more {
    font-size: 1.7rem;
    margin-bottom: 1.5rem;
    color: var(--text-dark);
}

.course-action p {
    font-size: 1.15rem;
    margin-bottom: 2rem;
    line-height: 1.6;
    color: var(--text-medium);
    max-width: 90%;
}

.btn-course-details {
    display: inline-block;
    padding: 1rem 2rem;
    background: var(--primary-color);
    color: white;
    font-size: 1.2rem;
    border-radius: var(--border-radius-lg);
    text-decoration: none;
    box-shadow: 0 5px 15px rgba(73, 97, 220, 0.3);
    transition: all var(--transition-fast);
    margin-top: 1rem;
    position: relative;
    overflow: hidden;
    z-index: 1;
}

.btn-course-details::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: var(--primary-dark);
    transition: all 0.4s ease;
    z-index: -1;
}

.btn-course-details:hover {
    color: #ffffff; /* 保持文字在背景上可见 */
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(73, 97, 220, 0.4);
}

.btn-course-details:hover::before {
    left: 0;
}

/* ================= 视频列表样式 ================= */
.video-list {
    width: 100%;
    max-width: 900px;
    margin: 2rem auto;
}

.video-item {
    display: flex;
    background: white;
    border-radius: var(--border-radius-sm);
    box-shadow: var(--shadow-light);
    margin-bottom: 1.5rem;
    overflow: hidden;
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
    position: relative;
}

.video-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-dark);
}

.video-thumbnail {
    flex: 0 0 30%;
    min-height: 180px;
    background-size: cover;
    background-position: center;
    position: relative;
    overflow: hidden;
}

.video-thumbnail::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.3);
    transition: all var(--transition-fast);
}

.video-item:hover .video-thumbnail::before {
    background: rgba(0, 0, 0, 0.1);
}

.video-play-icon {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 50px;
    height: 50px;
    background: rgba(255, 255, 255, 0.8);
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: all var(--transition-fast);
}

.video-item:hover .video-play-icon {
    transform: translate(-50%, -50%) scale(1.1);
    background: rgba(255, 255, 255, 0.9);
}

.video-play-icon i {
    color: var(--primary-color);
    font-size: 1.5rem;
    transition: all var(--transition-fast);
}

.video-item:hover .video-play-icon i {
    color: var(--primary-dark);
    transform: scale(1.1);
}

.video-info {
    flex: 1;
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
}

.video-title {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
    color: var(--text-dark);
    transition: color var(--transition-fast);
}

.video-item:hover .video-title {
    color: var(--primary-color);
}

.video-description {
    font-size: 1rem;
    color: var(--text-medium);
    margin-bottom: 1rem;
    flex: 1;
}

.video-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: var(--text-light);
    font-size: 0.9rem;
}

.video-btn {
    display: inline-block;
    padding: 0.6rem 1.2rem;
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: var(--border-radius-lg);
    font-weight: bold;
    transition: background-color var(--transition-fast), transform var(--transition-fast);
}

.video-btn:hover {
    color: #ffffff; /* 保持文字在背景上可见 */
    background-color: var(--primary-dark);
    transform: translateY(-3px);
}

/* ================= 页脚样式 ================= */
footer {
    background-color: #333;
    color: white;
    text-align: center;
    padding: 2rem;
}

/* ================= 动画效果 ================= */
.section-reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 1s ease, transform 1s ease;
}

.section-reveal.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ================= 响应式设计 ================= */
@media (max-width: 768px) {
    .navbar {
        padding: 0 5%;
    }
    
    .nav-links {
        position: fixed;
        background: white;
        height: 100vh;
        width: 100%;
        top: 70px;
        left: auto;
        right: -100%;
        flex-direction: column;
        align-items: center;
        justify-content: flex-start;
        padding-top: 2rem;
        transition: all var(--transition-medium);
        box-shadow: -5px 0 10px rgba(0, 0, 0, 0.1);
    }
    
    .nav-links.active {
        left: auto;
        right: 0;
    }
    
    .nav-links li {
        margin: 1.5rem 0;
    }
    
    .hamburger {
        display: block;
    }
    
    h1 {
        font-size: 2.5rem;
    }
    
    .welcome-subtitle {
        font-size: 1.5rem;
    }
    
    .course-container {
        flex-direction: column;
    }
    
    .course-slider {
        height: 400px;
    }
    
    .course-title {
        font-size: 2rem;
    }
    
    .course-description {
        font-size: 1.1rem;
        line-height: 1.6;
    }
    
    .video-item {
        flex-direction: column;
    }
    
    .video-thumbnail {
        flex: 0 0 150px;
        width: 100%;
    }
    
    .video-title {
        font-size: 1.3rem;
    }
    
    .gallery-item {
        min-width: 250px;
    }
    
    .btn-course-details {
        padding: 1rem 2rem;
        font-size: 1.1rem;
    }
    
    .scroll-down {
        bottom: 15px;
        padding: 8px 15px;
        font-size: 0.9rem;
    }
}

/* ================= 高级效果 ================= */
/* 悬停缩放效果 */
.hover-scale {
    transition: transform var(--transition-fast);
}

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

/* 卡片翻转效果 */
.flip-card {
    perspective: 1000px;
    width: 100%;
    height: 100%;
}

.flip-card-inner {
    position: relative;
    width: 100%;
    height: 100%;
    text-align: center;
    transition: transform 0.8s;
    transform-style: preserve-3d;
}

.flip-card:hover .flip-card-inner {
    transform: rotateY(180deg);
}

.flip-card-front, .flip-card-back {
    position: absolute;
    width: 100%;
    height: 100%;
    -webkit-backface-visibility: hidden;
    backface-visibility: hidden;
    border-radius: var(--border-radius-sm);
    overflow: hidden;
}

.flip-card-front {
    background-color: #fff;
}

.flip-card-back {
    background-color: var(--primary-color);
    color: white;
    transform: rotateY(180deg);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 2rem;
}

/* 文本渐变效果 */
.gradient-text {
    background: linear-gradient(45deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

/* 3D悬停效果增强 */
.tilt-effect {
    transform-style: preserve-3d;
    perspective: 1000px;
    transition: transform var(--transition-fast);
}

/* 阴影渐变效果 */
.shadow-gradient {
    position: relative;
}

.shadow-gradient::after {
    content: '';
    position: absolute;
    left: 0;
    right: 0;
    bottom: -15px;
    height: 15px;
    background: radial-gradient(ellipse at center, rgba(0,0,0,0.2) 0%, rgba(0,0,0,0) 80%);
    z-index: -1;
}

/* ================= 1. 页面加载动画 ================= */
.preloader {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: white;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 9999;
    transition: opacity 0.6s ease, visibility 0.6s ease;
}

.preloader.fade-out {
    opacity: 0;
    visibility: hidden;
}

.loader {
    width: 60px;
    height: 60px;
    border: 5px solid rgba(73, 97, 220, 0.2);
    border-radius: 50%;
    border-top-color: var(--primary-color);
    animation: spin 1s linear infinite;
    position: relative;
}

.loader::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 40px;
    height: 40px;
    border: 3px solid rgba(73, 97, 220, 0.2);
    border-radius: 50%;
    border-top-color: var(--primary-light);
    animation: spin 1.5s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* ================= 5. 微动画增强 ================= */
/* 按钮悬停效果增强 */
.btn-pulse {
    animation: pulse 2s infinite;
}

@keyframes pulse {
    0% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(73, 97, 220, 0.4);
    }
    70% {
        transform: scale(1.02);
        box-shadow: 0 0 0 10px rgba(73, 97, 220, 0);
    }
    100% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(73, 97, 220, 0);
    }
}

/* 图标动画效果 */
.icon-float {
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
    100% { transform: translateY(0); }
}

/* 滚动进入动画多样化 */
.fade-in-left {
    opacity: 0;
    transform: translateX(-30px);
    transition: opacity 1s ease, transform 1s ease;
}

.fade-in-right {
    opacity: 0;
    transform: translateX(30px);
    transition: opacity 1s ease, transform 1s ease;
}

.fade-in-left.visible, .fade-in-right.visible {
    opacity: 1;
    transform: translateX(0);
}

.fade-in-up {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 1s ease, transform 1s ease;
}

.fade-in-up.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ================= 7. 优化移动端体验 ================= */
/* 移动端触控优化 */
@media (max-width: 768px) {
    /* 增大按钮和可点击区域 */
    .btn-course-details, .course-button, .video-btn, .scroll-down {
        padding: 12px 24px;
        font-size: 1.1rem;
        min-height: 44px; /* 苹果推荐的最小触摸目标高度 */
    }
    
    /* 增加表单元素间距 */
    input, select, button {
        margin-bottom: 15px;
    }
    
    /* 优化导航 */
    .nav-links li {
        margin: 1.8rem 0;
    }
    
    .nav-links a {
        padding: 10px 0;
        display: block;
    }
    
    /* 改善触摸反馈 */
    .gallery-item, .video-item, .course-action {
        -webkit-tap-highlight-color: rgba(0,0,0,0);
    }
}

/* 添加滑动手势支持的视觉提示 */
.swipe-hint {
    position: absolute;
    bottom: 60px;
    left: 50%;
    transform: translateX(-50%);
    color: rgba(255, 255, 255, 0.7);
    font-size: 0.9rem;
    display: none;
}

.swipe-arrow {
    display: inline-block;
    animation: swipeMove 1.5s ease infinite;
    margin: 0 5px;
}

@keyframes swipeMove {
    0% { transform: translateX(-5px); }
    50% { transform: translateX(5px); }
    100% { transform: translateX(-5px); }
}

@media (max-width: 768px) {
    .swipe-hint {
        display: block;
    }
}

/* ================= 9. 背景优化 ================= */
/* SVG波浪背景 */
.wave-bg {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 80px;
    background: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1440 320"><path fill="%23ffffff" fill-opacity="1" d="M0,224L48,218.7C96,213,192,203,288,181.3C384,160,480,128,576,138.7C672,149,768,203,864,208C960,213,1056,171,1152,160C1248,149,1344,171,1392,181.3L1440,192L1440,320L1392,320C1344,320,1248,320,1152,320C1056,320,960,320,864,320C768,320,672,320,576,320C480,320,384,320,288,320C192,320,96,320,48,320L0,320Z"></path></svg>');
    background-size: cover;
    background-repeat: no-repeat;
    z-index: 2;
}

/* 几何装饰 */
.geometric-bg {
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    overflow: hidden;
    z-index: 0;
    opacity: 0.1;
}

.shape {
    position: absolute;
    border-radius: 50%;
    background: var(--primary-light);
    animation: shapeFloat 15s linear infinite;
}

.shape-1 {
    width: 150px;
    height: 150px;
    top: 10%;
    left: 5%;
    opacity: 0.5;
    animation-duration: 25s;
}

.shape-2 {
    width: 80px;
    height: 80px;
    bottom: 20%;
    right: 10%;
    background: var(--secondary-color);
    opacity: 0.3;
    animation-duration: 20s;
    animation-delay: 2s;
}

.shape-3 {
    width: 120px;
    height: 120px;
    top: 50%;
    right: 5%;
    opacity: 0.4;
    animation-duration: 30s;
    animation-delay: 5s;
}

@keyframes shapeFloat {
    0% {
        transform: translateY(0) rotate(0deg);
    }
    50% {
        transform: translateY(-20px) rotate(180deg);
    }
    100% {
        transform: translateY(0) rotate(360deg);
    }
}

/* 微妙的纹理背景 */
.texture-bg {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="20" height="20"><rect width="20" height="20" fill="none"/><rect width="1" height="1" fill="%23f5f5f5"/></svg>');
    z-index: -1;
    opacity: 0.5;
}

/* 增强视觉分层 */
#articles, #videos {
    position: relative;
    z-index: 1;
    overflow: hidden;
}

#articles::before, #videos::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle at top right, rgba(106, 152, 240, 0.05), transparent 70%);
    z-index: -1;
}

#videos::before {
    background: radial-gradient(circle at bottom left, rgba(73, 97, 220, 0.05), transparent 70%);
}

/* ================= 10. 性能优化 ================= */
/* 改进的焦点样式 */
:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

:focus:not(:focus-visible) {
    outline: none;
}

/* 减少重绘和回流 */
.hardware-accelerated {
    transform: translateZ(0);
    backface-visibility: hidden;
    perspective: 1000px;
}

/* ================= 全屏图片查看器 ================= */
.fullscreen-viewer {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.9);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 2000;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.fullscreen-viewer.active {
    opacity: 1;
}

.viewer-content {
    max-width: 90%;
    max-height: 90%;
    position: relative;
    text-align: center;
}

.viewer-content img {
    max-width: 100%;
    max-height: 80vh;
    box-shadow: 0 5px 15px rgba(0,0,0,0.3);
    border: 5px solid white;
}

.viewer-content p {
    color: white;
    margin-top: 20px;
    font-size: 1.2rem;
}

.close-viewer {
    position: absolute;
    top: -30px;
    right: -30px;
    background: white;
    border: none;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    color: #333;
    box-shadow: 0 2px 10px rgba(0,0,0,0.2);
    transition: all 0.3s ease;
}

.close-viewer:hover {
    transform: scale(1.1);
    box-shadow: 0 4px 15px rgba(0,0,0,0.3);
}

/* 图片光影效果 */
.glare {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1;
    pointer-events: none;
}

/* ================= 回到顶部按钮 ================= */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: var(--primary-color);
    color: white;
    border: none;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    opacity: 0;
    transform: translateY(20px);
    transition: all 0.3s ease;
    box-shadow: 0 4px 10px rgba(0,0,0,0.15);
    z-index: 99;
}

.back-to-top.visible {
    opacity: 1;
    transform: translateY(0);
}

.back-to-top:hover {
    background-color: var(--primary-dark);
    transform: translateY(-5px);
    box-shadow: 0 6px 15px rgba(0,0,0,0.2);
}

/* ================= 辅助功能工具栏 ================= */
.accessibility-bar {
    position: fixed;
    bottom: 30px;
    left: 30px;
    z-index: 990;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.access-toggle {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: var(--primary-color);
    color: white;
    border: none;
    cursor: pointer;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    box-shadow: 0 4px 10px rgba(0,0,0,0.15);
    z-index: 991;
    transition: all 0.3s ease;
}

.access-toggle:hover {
    background-color: var(--primary-dark);
    transform: scale(1.1);
}

.access-options {
    display: none;
    opacity: 0;
    flex-direction: column;
    background: white;
    border-radius: 10px;
    padding: 15px;
    margin-top: 10px;
    box-shadow: 0 5px 15px rgba(0,0,0,0.1);
    transition: opacity 0.3s ease;
}

.access-options button {
    margin: 5px 0;
    padding: 10px 15px;
    border: none;
    background: var(--bg-light);
    border-radius: 5px;
    cursor: pointer;
    display: flex;
    align-items: center;
    color: var(--text-dark);
    transition: all 0.2s ease;
}

.access-options button i {
    margin-right: 10px;
    color: var(--primary-color);
}

.access-options button:hover {
    background: var(--bg-medium);
}

.access-options button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* 高对比度模式 - 优化配色方案 */
body.high-contrast {
    background-color: #0a1a2f; /* 深蓝色背景替代纯黑 */
    color: #f0f0f0; /* 柔和的白色 */
}

body.high-contrast .navbar {
    background-color: #0a1a2f;
    color: #f0f0f0;
    border-bottom: 1px solid #4a90e2;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.4);
}

body.high-contrast .course-action,
body.high-contrast .video-item {
    background-color: #10243d; /* 稍微浅一点的蓝色 */
    color: #f0f0f0;
    border: 1px solid #4a90e2;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
}

body.high-contrast a,
body.high-contrast .nav-links a {
    color: #4a90e2; /* 明亮的蓝色 */
}

body.high-contrast h1,
body.high-contrast h2,
body.high-contrast h3 {
    color: #ffd166; /* 温暖的金色 */
}

body.high-contrast .btn-course-details,
body.high-contrast .course-button,
body.high-contrast .video-btn {
    background-color: #1a365d; /* 深蓝色按钮 */
    color: #ffffff;
    border: 2px solid #4a90e2;
}

body.high-contrast .btn-course-details:hover,
body.high-contrast .course-button:hover,
body.high-contrast .video-btn:hover {
    background-color: #2c4f82; /* 悬停时稍微变亮 */
    transform: translateY(-3px);
}

/* 欢迎页高对比度样式 */
body.high-contrast #welcome {
    background: linear-gradient(135deg, #0f2847, #0a1a2f); /* 渐变背景更有深度 */
    color: #f0f0f0;
    border-bottom: 1px solid #4a90e2;
}

body.high-contrast #welcome .welcome-gallery {
    background-color: #0f2847;
    border-top: 1px solid rgba(74, 144, 226, 0.3);
}

body.high-contrast #welcome .gallery-item {
    background-color: #10243d;
    border: 1px solid #4a90e2;
}

body.high-contrast #welcome .gallery-caption {
    color: #ffd166;
}

body.high-contrast .welcome-subtitle {
    color: #e0e0e0;
}

body.high-contrast .scroll-down {
    background-color: #1a365d;
    color: #fff;
    border: 1px solid #4a90e2;
}

body.high-contrast .section-title {
    color: #ffd166;
}

body.high-contrast .section-title::after {
    background: #4a90e2;
}

body.high-contrast footer {
    background-color: #071525;
    border-top: 1px solid #4a90e2;
}

/* 课程卡片高对比度样式 */
body.high-contrast .course-card::before {
    background: linear-gradient(to top, rgba(7, 21, 37, 0.9), rgba(7, 21, 37, 0.5));
}

body.high-contrast .course-slider {
    background: linear-gradient(135deg, #0f2847, #0a1a2f);
}

body.high-contrast .course-title::after {
    background: #4a90e2;
}

/* 视频区域高对比度样式 */
body.high-contrast .video-thumbnail::before {
    background: rgba(10, 26, 47, 0.5);
}

body.high-contrast .video-play-icon {
    background: rgba(255, 255, 255, 0.9);
}

body.high-contrast .video-play-icon i {
    color: #0a1a2f;
}

/* 修复全屏查看器高对比度样式 */
body.high-contrast .fullscreen-viewer {
    background-color: rgba(7, 21, 37, 0.95);
}

body.high-contrast .viewer-content img {
    border: 3px solid #4a90e2;
}

body.high-contrast .close-viewer {
    background-color: #1a365d;
    color: #fff;
    border: 1px solid #4a90e2;
}

/* 辅助功能工具栏高对比度样式 */
body.high-contrast .access-toggle,
body.high-contrast .back-to-top {
    background-color: #1a365d;
    border: 1px solid #4a90e2;
}

body.high-contrast .access-options {
    background: #10243d;
    border: 1px solid #4a90e2;
}

body.high-contrast .access-options button {
    background: #0a1a2f;
    color: #f0f0f0;
    border: 1px solid #4a90e2;
}

body.high-contrast .access-options button:hover {
    background: #1a365d;
}

body.high-contrast .access-options button i {
    color: #4a90e2;
}

/* ================= 统计数字区域 ================= */
.stats-section {
    padding: 60px 20px;
    background: linear-gradient(135deg, var(--bg-light), var(--bg-medium));
    border-top: 1px solid rgba(0,0,0,0.05);
    border-bottom: 1px solid rgba(0,0,0,0.05);
}

.stats-container {
    display: flex;
    justify-content: space-around;
    max-width: 1200px;
    margin: 0 auto;
    flex-wrap: wrap;
}

.stat-item {
    text-align: center;
    padding: 20px;
    flex: 1;
    min-width: 200px;
    margin: 10px;
    background: white;
    border-radius: var(--border-radius-md);
    box-shadow: var(--shadow-medium);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.stat-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-dark);
}

.stat-item i {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 15px;
}

.stat-count {
    font-size: 3rem;
    font-weight: bold;
    color: var(--primary-dark);
    line-height: 1.2;
    margin-bottom: 5px;
}

.stat-label {
    font-size: 1.1rem;
    color: var(--text-medium);
}

/* 移动设备适配 */
@media (max-width: 768px) {
    .stat-item {
        min-width: 140px;
        padding: 15px;
    }
    
    .stat-count {
        font-size: 2.2rem;
    }
    
    .stat-item i {
        font-size: 2rem;
    }
    
    .back-to-top,
    .access-toggle {
        width: 40px;
        height: 40px;
        font-size: 1rem;
    }
    
    .back-to-top {
        bottom: 20px;
        right: 20px;
    }
    
    .accessibility-bar {
        bottom: 20px;
        left: 20px;
    }
    
    .close-viewer {
        top: -20px;
        right: -20px;
        width: 30px;
        height: 30px;
    }
}

/* 课程卡片滑动动画 */
.slide-out {
    animation: slideOutLeft 0.3s forwards;
}

@keyframes slideOutLeft {
    from {
        transform: translateX(0);
        opacity: 1;
    }
    to {
        transform: translateX(-30px);
        opacity: 0;
    }
}

/* 触摸反馈效果 */
.touched {
    transform: scale(0.98);
    box-shadow: var(--shadow-light);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}