/* 全局样式 */
:root {
    --primary-color: #3498db;
    --secondary-color: #2980b9;
    --text-color: #333;
    --bg-color: #f5f5f5;
    --light-gray: #e0e0e0;
    --dark-gray: #888;
    --white: #fff;
    --border-radius: 5px;
    --box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    color: var(--text-color);
    background-color: var(--bg-color);
    line-height: 1.6;
}

/* 导航栏样式 */
.navbar {
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    padding: 12px 0;
}

.navbar-brand {
    font-size: 1.5rem;
    font-weight: 600;
}

.navbar-nav .nav-link {
    font-weight: 500;
    padding: 0.5rem 1rem;
    transition: all 0.3s;
}

.navbar-nav .nav-link:hover {
    color: var(--light-gray) !important;
}

/* 主内容区域 */
.main-content {
    margin-top: 30px;
    margin-bottom: 50px;
}

/* 侧边栏样式 */
.sidebar {
    background-color: var(--white);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 0;
    margin-bottom: 30px;
}

.sidebar-header {
    background-color: var(--primary-color);
    color: var(--white);
    padding: 15px;
    border-top-left-radius: var(--border-radius);
    border-top-right-radius: var(--border-radius);
}

.sidebar-header h4 {
    margin: 0;
    font-size: 1.2rem;
    font-weight: 600;
}

.list-group-item {
    cursor: pointer;
    border-left: none;
    border-right: none;
    padding: 12px 15px;
    transition: all 0.3s;
}

.list-group-item:first-child {
    border-top: none;
}

.list-group-item:hover {
    background-color: #f0f7ff;
}

.list-group-item.active {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
}

/* 内容区域样式 */
.content-area {
    background-color: var(--white);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    padding: 25px;
}

.content-header {
    margin-bottom: 25px;
    border-bottom: 1px solid var(--light-gray);
    padding-bottom: 15px;
}

.content-header h2 {
    font-size: 1.8rem;
    font-weight: 600;
    color: var(--primary-color);
    margin: 0 0 10px;
}

.breadcrumb {
    margin-bottom: 0;
    background: none;
    padding: 0;
}

.breadcrumb-item a {
    color: var(--primary-color);
    text-decoration: none;
}

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

/* 视频播放器样式 */
.video-player-container {
    background-color: #f8f9fa;
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 30px;
}

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

.video-player video {
    width: 100%;
    height: auto;
    display: block;
}

.player-controls {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background: linear-gradient(to top, rgba(0, 0, 0, 0.7), transparent);
    padding: 15px;
    transition: opacity 0.3s;
    opacity: 0;
}

.video-player:hover .player-controls {
    opacity: 1;
}

.progress-container {
    height: 5px;
    background-color: rgba(255, 255, 255, 0.3);
    margin-bottom: 10px;
    cursor: pointer;
    border-radius: 3px;
}

.progress-bar {
    height: 100%;
    background-color: var(--primary-color);
    width: 0;
    border-radius: 3px;
}

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

.control-btn {
    background: none;
    border: none;
    color: var(--white);
    cursor: pointer;
    padding: 5px;
    margin-right: 10px;
    opacity: 0.8;
    transition: opacity 0.2s;
}

.control-btn:hover {
    opacity: 1;
}

.control-btn img {
    width: 20px;
    height: 20px;
}

.volume-control, .speed-control {
    position: relative;
    display: flex;
    align-items: center;
}

.volume-slider {
    width: 0;
    overflow: hidden;
    transition: width 0.3s;
    margin-left: 5px;
}

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

.volume-slider input {
    width: 100%;
    cursor: pointer;
}

.time-display {
    color: var(--white);
    font-size: 0.9rem;
    margin: 0 15px;
}

.speed-options {
    position: absolute;
    bottom: 40px;
    right: 0;
    background-color: rgba(0, 0, 0, 0.8);
    border-radius: 5px;
    padding: 5px 0;
    display: none;
    width: 80px;
}

.speed-control:hover .speed-options {
    display: block;
}

.speed-option {
    padding: 5px 15px;
    cursor: pointer;
    color: var(--white);
    transition: background-color 0.2s;
    text-align: center;
}

.speed-option:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

#speedBtn {
    width: 40px;
    text-align: center;
}

/* 功能描述区域样式 */
.feature-description {
    margin-top: 30px;
}

.feature-description h3 {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 20px;
}

.feature-card {
    background-color: #f8f9fa;
    border-radius: var(--border-radius);
    padding: 20px;
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    transition: transform 0.3s, box-shadow 0.3s;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--box-shadow);
}

.feature-icon {
    margin-right: 15px;
}

.feature-icon img {
    width: 40px;
    height: 40px;
}

.feature-text h4 {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 5px;
    color: var(--secondary-color);
}

.feature-text p {
    margin: 0;
    color: var(--dark-gray);
}

/* 页脚样式 */
.footer {
    background-color: #2c3e50;
    color: var(--white);
    padding: 40px 0 20px;
}

.footer h5 {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 20px;
    color: var(--primary-color);
}

.footer p {
    font-size: 0.9rem;
    opacity: 0.8;
}

.footer-links {
    list-style: none;
    padding: 0;
    margin: 0;
}

.footer-links li {
    margin-bottom: 10px;
}

.footer-links a {
    color: var(--white);
    opacity: 0.8;
    text-decoration: none;
    transition: opacity 0.2s;
}

.footer-links a:hover {
    opacity: 1;
    text-decoration: underline;
}

.footer-bottom {
    text-align: center;
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    margin: 0;
    font-size: 0.9rem;
    opacity: 0.6;
}

/* 响应式设计 */
@media (max-width: 992px) {
    .sidebar {
        margin-bottom: 30px;
    }
    
    .content-area {
        padding: 20px;
    }
    
    /* 改变内容顺序，在小屏幕设备上调整 */
    .row {
        display: flex;
        flex-direction: column;
    }
    
    .content-area {
        order: 1; /* 内容区域放在前面 */
    }
    
    .sidebar {
        order: 2; /* 侧边栏放在后面 */
        margin-top: 30px;
        box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.05);
    }
    
    /* 手机端菜单标题样式 */
    .mobile-menu-title {
        display: block;
        text-align: center;
        font-size: 1.2rem;
        font-weight: 600;
        margin: 20px 0 15px;
        color: var(--primary-color);
    }
    
    /* 在手机端优化列表样式 */
    .list-group-item {
        text-align: center;
        padding: 12px 10px;
    }
    
    /* 手机端分隔线 */
    .mobile-divider {
        display: block;
        height: 1px;
        background: linear-gradient(to right, transparent, var(--light-gray), transparent);
        margin: 30px 0;
    }
}

@media (max-width: 768px) {
    .navbar-brand {
        font-size: 1.3rem;
    }
    
    .content-header h2 {
        font-size: 1.5rem;
    }
    
    .feature-card {
        flex-direction: column;
        text-align: center;
    }
    
    .feature-icon {
        margin-right: 0;
        margin-bottom: 15px;
    }
    
    .feature-icon img {
        width: 50px;
        height: 50px;
    }
    
    .footer h5 {
        margin-top: 20px;
    }
    
    /* 增强移动端的可触摸区域 */
    .list-group-item {
        padding: 15px 10px;
    }
}

@media (max-width: 576px) {
    .content-area {
        padding: 15px;
    }
    
    .video-player-container {
        padding: 10px;
    }
    
    .controls-buttons {
        flex-wrap: wrap;
    }
    
    .time-display {
        order: -1;
        width: 100%;
        margin: 0 0 10px;
        text-align: center;
    }
    
    .feature-description h3 {
        font-size: 1.3rem;
    }
    
    .feature-card {
        padding: 15px;
    }
}

/* 视频描述样式 */
.video-description {
    background-color: #f0f7ff;
    border-left: 4px solid var(--primary-color);
    padding: 15px;
    margin: 15px 0 25px;
    font-size: 1rem;
    line-height: 1.6;
    color: #555;
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
}