/* 全局样式 */
@import url('https://fonts.googleapis.com/css2?family=Noto+Sans+SC:wght@300;400;500;700&display=swap');

:root {
    --primary-color: #1976D2;
    --primary-light: #42A5F5;
    --primary-dark: #0D47A1;
    --accent-color: #03A9F4;
    --text-light: #FFFFFF;
    --text-dark: #263238;
    --background-light: #F5F7FA;
    --card-bg: #FFFFFF;
    --shadow-light: 0 2px 10px rgba(0, 0, 0, 0.05);
    --shadow-medium: 0 4px 20px rgba(0, 0, 0, 0.1);
    --transition-speed: 0.3s;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Noto Sans SC', 'Source Han Sans CN', 'Microsoft YaHei', sans-serif;
}

body {
    background-color: var(--background-light);
    color: var(--text-dark);
    line-height: 1.6;
}

.container {
    display: flex;
    min-height: 100vh;
    width: 100%;
}

/* 左侧导航面板样式 - 卡片式设计 */
.sidebar {
    width: 30%;
    background: linear-gradient(135deg, var(--primary-dark), var(--primary-color));
    color: var(--text-light);
    padding: 25px 20px;
    box-shadow: var(--shadow-medium);
    overflow-y: auto;
    transition: all var(--transition-speed) ease;
}

.sidebar h2 {
    text-align: center;
    margin-bottom: 30px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--accent-color);
    color: var(--text-light);
    font-weight: 500;
    letter-spacing: 1px;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.nav-section {
    background-color: rgba(255, 255, 255, 0.1);
    border-radius: 10px;
    padding: 15px;
    margin-bottom: 25px;
    box-shadow: var(--shadow-light);
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
}

.nav-section:hover {
    transform: translateY(-3px);
    box-shadow: 0 6px 25px rgba(0, 0, 0, 0.15);
}

.nav-section label {
    display: block;
    margin-bottom: 10px;
    font-weight: 500;
    color: var(--text-light);
    letter-spacing: 0.5px;
}

.dropdown {
    width: 100%;
    padding: 12px 15px;
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: 8px;
    background-color: rgba(0, 0, 0, 0.2);
    color: var(--text-light);
    font-size: 16px;
    cursor: pointer;
    transition: all var(--transition-speed);
    outline: none;
    appearance: none;
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='white'%3e%3cpath d='M7 10l5 5 5-5z'/%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right 10px center;
    background-size: 20px;
    padding-right: 30px;
}

.dropdown:hover:not(:disabled) {
    background-color: rgba(0, 0, 0, 0.3);
    border-color: rgba(255, 255, 255, 0.3);
}

/* 下拉列表选项样式 */
.dropdown option {
    background-color: #34495e;
    color: white;
}

.dropdown:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.knowledge-list {
    list-style-type: none;
    margin-top: 15px;
}

.knowledge-list li {
    padding: 12px 15px;
    margin-bottom: 8px;
    background-color: rgba(255, 255, 255, 0.15);
    border-radius: 8px;
    cursor: pointer;
    transition: all var(--transition-speed);
    position: relative;
    overflow: hidden;
}

.knowledge-list li::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background-color: var(--accent-color);
    transform: scaleY(0);
    transition: transform var(--transition-speed);
}

.knowledge-list li:hover {
    background-color: rgba(255, 255, 255, 0.25);
    transform: translateX(5px);
}

.knowledge-list li:hover::before {
    transform: scaleY(1);
}

.knowledge-list li.active {
    background-color: var(--accent-color);
    font-weight: 500;
    box-shadow: 0 4px 10px rgba(3, 169, 244, 0.3);
    transform: translateX(5px);
}

.knowledge-list li.active::before {
    transform: scaleY(1);
    background-color: var(--text-light);
}

.empty-message {
    font-style: italic;
    opacity: 0.7;
    cursor: default;
    text-align: center;
}

.empty-message:hover {
    background-color: rgba(255, 255, 255, 0.15);
    transform: none;
}

/* 右侧内容区域样式 */
.content {
    width: 70%;
    padding: 30px;
    display: flex;
    flex-direction: column;
    background-color: var(--background-light);
    transition: all var(--transition-speed);
}

.content-header {
    padding-bottom: 20px;
    margin-bottom: 25px;
    border-bottom: 3px solid var(--primary-light);
    position: relative;
}

.content-header::after {
    content: '';
    position: absolute;
    bottom: -3px;
    left: 0;
    width: 100px;
    height: 3px;
    background-color: var(--primary-color);
}

.content-header h1 {
    color: var(--primary-dark);
    font-weight: 500;
    letter-spacing: 0.5px;
    position: relative;
    display: inline-block;
}

.content-body {
    flex-grow: 1;
    background-color: var(--card-bg);
    padding: 25px;
    border-radius: 12px;
    box-shadow: var(--shadow-medium);
    margin-bottom: 25px;
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
}

.content-body:hover {
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

.topic-content {
    line-height: 1.8;
    font-size: 16px;
}

.experiment-area {
    background-color: var(--card-bg);
    padding: 25px;
    border-radius: 12px;
    box-shadow: var(--shadow-medium);
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
}

.experiment-area:hover {
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

.experiment-area h3 {
    color: var(--primary-color);
    margin-bottom: 20px;
    padding-bottom: 12px;
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
    font-weight: 500;
    position: relative;
}

.experiment-area h3::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 0;
    width: 60px;
    height: 2px;
    background-color: var(--primary-light);
}

.experiment-content {
    padding: 10px;
}

.experiment-demo h4 {
    color: var(--text-dark);
    margin-bottom: 15px;
}

.experiment-link {
    text-decoration: none;
    color: var(--text-dark);
    display: block;
}

.video-thumbnail {
    background-color: rgba(0, 0, 0, 0.05);
    border-radius: 8px;
    padding: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
    transition: all var(--transition-speed);
    border: 1px solid rgba(0, 0, 0, 0.1);
}

.video-thumbnail:hover {
    background-color: rgba(0, 0, 0, 0.1);
    transform: translateY(-3px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

.play-icon {
    font-size: 24px;
    color: var(--accent-color);
}

/* 响应式设计优化 */
@media (max-width: 1024px) {
    .sidebar, .content {
        padding: 20px;
    }
}

@media (max-width: 768px) {
    .container {
        flex-direction: column;
    }
    
    .sidebar, .content {
        width: 100%;
    }
    
    .sidebar {
        order: 1;
        padding: 20px 15px;
    }
    
    .content {
        order: 2;
        padding: 20px 15px;
    }
    
    .nav-section {
        padding: 12px;
    }
    
    .content-body, .experiment-area {
        padding: 20px;
    }
}

/* 添加过渡动画 */
.fade-enter-active, .fade-leave-active {
    transition: opacity var(--transition-speed);
}
.fade-enter, .fade-leave-to {
    opacity: 0;
}

.slide-enter-active, .slide-leave-active {
    transition: transform var(--transition-speed);
}
.slide-enter, .slide-leave-to {
    transform: translateX(-20px);
    opacity: 0;
}

/* 滚动条美化 */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 10px;
}

::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.2);
    border-radius: 10px;
}

::-webkit-scrollbar-thumb:hover {
    background: rgba(255, 255, 255, 0.3);
}