/* 基本样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Microsoft YaHei', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f5f5f5;
}

#main-container {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* 头部样式 */
header {
    background-color: #005792;
    color: white;
    padding: 1rem 2rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

header h1 {
    margin-bottom: 1rem;
    font-size: 1.8rem;
}

/* 导航样式 */
#main-nav ul {
    display: flex;
    list-style: none;
    gap: 1rem;
}

.nav-link {
    color: white;
    text-decoration: none;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: background-color 0.3s;
}

.nav-link:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

.nav-link.active {
    background-color: rgba(255, 255, 255, 0.3);
    font-weight: bold;
}

/* 主内容区域 */
main {
    flex: 1;
    padding: 2rem;
    max-width: 1200px;
    margin: 0 auto;
    width: 100%;
    position: relative;
}

/* 加载指示器 */
#loading-indicator {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: rgba(255, 255, 255, 0.9);
    padding: 1rem 2rem;
    border-radius: 8px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    display: none;
    z-index: 100;
}

/* 页面部分 */
.page-section {
    background-color: white;
    border-radius: 8px;
    padding: 2rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    margin-bottom: 2rem;
}

.page-section h2 {
    color: #005792;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid #f0f0f0;
}

.page-section h3 {
    color: #0078aa;
    margin: 1.5rem 0 0.5rem;
}

.page-section p {
    margin-bottom: 1rem;
}

/* 卡片容器 */
.card-container {
    display: flex;
    gap: 2rem;
    margin-top: 2rem;
    flex-wrap: wrap;
}

.feature-card {
    flex: 1;
    min-width: 250px;
    background-color: #f9f9f9;
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    transition: transform 0.3s;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.feature-card h3 {
    color: #005792;
    margin-bottom: 0.5rem;
}

/* 按钮样式 */
.btn {
    display: inline-block;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    text-decoration: none;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    font-weight: 500;
    border: none;
    margin-top: 1rem;
}

.btn-primary {
    background-color: #005792;
    color: white;
}

.btn-primary:hover {
    background-color: #004a7c;
}

.btn-outline {
    background-color: transparent;
    border: 1px solid #005792;
    color: #005792;
}

.btn-outline:hover {
    background-color: #005792;
    color: white;
}

.btn-secondary {
    background-color: #6c757d;
    color: white;
}

.btn-secondary:hover {
    background-color: #5a6268;
}

/* 学习卡片 */
.lesson-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.lesson-card {
    background-color: #f9f9f9;
    border-radius: 8px;
    padding: 1.5rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    transition: transform 0.3s;
}

.lesson-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

/* 测验样式 */
.quiz-container {
    background-color: #f9f9f9;
    border-radius: 8px;
    padding: 2rem;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.quiz-intro {
    text-align: center;
    padding: 2rem;
}

.quiz-question {
    margin-bottom: 2rem;
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin: 1.5rem 0;
}

.quiz-option {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem;
    border-radius: 4px;
    background-color: #fff;
    transition: background-color 0.3s;
    cursor: pointer;
}

.quiz-option:hover {
    background-color: #f0f0f0;
}

.quiz-next {
    margin-top: 1.5rem;
}

/* 错误消息 */
.error-message {
    background-color: #fff3f3;
    border-left: 4px solid #dc3545;
    padding: 1rem 1.5rem;
    border-radius: 4px;
    margin-bottom: 1rem;
}

.error-message h2 {
    color: #dc3545;
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
}

/* 页脚样式 */
footer {
    background-color: #333;
    color: #f0f0f0;
    text-align: center;
    padding: 1.5rem;
    margin-top: auto;
}

/* 响应式设计 */
@media (max-width: 768px) {
    header {
        padding: 1rem;
    }

    #main-nav ul {
        flex-direction: column;
        gap: 0.5rem;
    }

    main {
        padding: 1rem;
    }

    .card-container {
        flex-direction: column;
    }

    .lesson-grid {
        grid-template-columns: 1fr;
    }
}