/* 基础样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

/* CSS变量定义 */
:root {
    --primary-color: #3498db;
    --secondary-color: #2c3e50;
    --bg-color: #F5F5F5;
    --card-color: #FFFFFF;
    --text-primary: #333333;
    --text-secondary: #666666;
    --text-light: #999999;
    --border-color: #E0E0E0;
    --divider-color: #E5E5E5;
    --active-color: #07C160;
    --warning-color: #FF9500;
    --error-color: #FF3B30;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --hover-overlay: rgba(0, 0, 0, 0.05);
    --active-overlay: rgba(52, 152, 219, 0.1);
    
    /* 字体大小基准 */
    font-size: 16px;
}

/* 主体样式 */
body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.8;
    min-height: 100vh;
}

/* 顶部导航 */
.header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: clamp(0.75rem, 2vw, 0.9375rem);
    display: flex;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 10;
}

.back-btn {
    color: white;
    font-size: clamp(1.5rem, 3vw, 1.75rem);
    background: none;
    border: 0.2rem solid #ffffff;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: clamp(0.25rem, 0.75vw, 0.3125rem);
    padding: clamp( 0.3rem, 0.75vw, 0.3125rem);
    border-radius: 10%;
    transition: background-color 0.2s;
}

.back-btn:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

.header-title {
    font-size: clamp(1.5rem, 3vw, 2rem);
    font-weight: 500;
    text-align: center;
    flex: 1;
    padding-right: clamp(2.5rem, 6vw, 3rem);
}

/* 容器 */
.container {
    padding: 1rem;
    max-width: 56.25rem;
    margin: 0 auto;
}

/* 协议目录 */
.agreement-nav {
    background: var(--card-color);
    border-radius: 0.75rem;
    padding: 1.5rem;
    margin-bottom: 1.25rem;
    box-shadow: 0 0.125rem 0.5rem var(--shadow-color);
    border: 0.0625rem solid var(--border-color);
}

.nav-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.25rem;
    color: var(--text-primary);
    padding-bottom: 0.75rem;
    border-bottom: 0.0625rem solid var(--divider-color);
}

.nav-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(15.625rem, 1fr));
    gap: 0.75rem;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem;
    border-radius: 0.5rem;
    transition: all 0.2s ease;
    cursor: pointer;
    text-decoration: none;
    color: var(--text-primary);
    border: 0.0625rem solid transparent;
    background: var(--bg-color);
}

.nav-item:hover {
    background: var(--hover-overlay);
    border-color: var(--primary-color);
}

.nav-item.active {
    background: var(--active-overlay);
    border-color: var(--primary-color);
    box-shadow: 0 0.125rem 0.5rem rgba(52, 152, 219, 0.2);
}

.nav-icon {
    font-size: 1.5rem;
    width: 2rem;
    text-align: center;
    color: var(--primary-color);
}

.nav-text {
    flex: 1;
    font-size: 1rem;
    font-weight: 500;
}

/* 协议内容 */
.agreement-content {
    background: var(--card-color);
    border-radius: 0.75rem;
    padding: 2rem;
    box-shadow: 0 0.125rem 0.5rem var(--shadow-color);
    border: 0.0625rem solid var(--border-color);
}

.agreement-header {
    border-bottom: 0.125rem solid var(--primary-color);
    padding-bottom: 1.25rem;
    margin-bottom: 2rem;
}

.agreement-title {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
}

.agreement-meta {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    font-size: 0.875rem;
    color: var(--text-light);
}

.agreement-body {
    font-size: 1rem;
    color: var(--text-secondary);
    line-height: 1.7;
}

/* 章节 */
.section {
    margin-bottom: 2.5rem;
    padding: 1.25rem;
    border-radius: 0.5rem;
    background: rgba(245, 245, 245, 0.5);
}

.section-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.25rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding-bottom: 0.75rem;
    border-bottom: 0.0625rem solid var(--divider-color);
}

.section-icon {
    color: var(--primary-color);
    font-size: 1.2rem;
}

/* 条款 */
.article {
    margin-bottom: 1.5rem;
}

.article-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
    padding-left: 0.5rem;
    border-left: 0.1875rem solid var(--primary-color);
}

.article-content {
    margin-bottom: 1rem;
    text-align: justify;
}

/* 条款列表 */
.clause {
    margin-bottom: 0.875rem;
    padding-left: 1.75rem;
    position: relative;
    line-height: 1.6;
}

.clause::before {
    content: "•";
    position: absolute;
    left: 0.75rem;
    color: var(--primary-color);
    font-weight: bold;
    font-size: 1.2rem;
}

/* 强调框 */
.highlight {
    background: linear-gradient(135deg, rgba(7, 193, 96, 0.1), rgba(7, 193, 96, 0.05));
    padding: 1.25rem;
    border-radius: 0.5rem;
    border-left: 0.25rem solid var(--active-color);
    margin: 1.25rem 0;
    color: var(--text-secondary);
}

.highlight strong {
    color: var(--active-color);
}

/* 提示框 */
.note {
    background: linear-gradient(135deg, rgba(255, 149, 0, 0.1), rgba(255, 149, 0, 0.05));
    padding: 1.25rem;
    border-radius: 0.5rem;
    border-left: 0.25rem solid var(--warning-color);
    margin: 1.25rem 0;
    color: var(--text-secondary);
    font-style: italic;
}

/* 返回顶部按钮 */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 3rem;
    height: 3rem;
    background: var(--primary-color);
    color: var(--card-color);
    border: none;
    border-radius: 50%;
    cursor: pointer;
    display: none;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    box-shadow: 0 0.125rem 0.5rem rgba(0, 0, 0, 0.2);
    transition: all 0.3s ease;
    z-index: 99;
}

.back-to-top:hover {
    background: var(--secondary-color);
}


/* 动画 */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(0.625rem);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(1.25rem);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

/* 响应式设计 */
@media (max-width: 48rem) {
    .container {
        padding: 0.75rem;
    }
    
    .nav-list {
        grid-template-columns: 1fr;
    }
    
    .agreement-meta {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.5rem;
    }
    
    .agreement-content {
        padding: 1.5rem;
    }
    
    .back-to-top {
        bottom: 1rem;
        right: 1rem;
        width: 2.5rem;
        height: 2.5rem;
        font-size: 1.25rem;
    }
}

@media (max-width: 30rem) {
    .header-title {
        font-size: 1rem;
    }
    
    .agreement-title {
        font-size: 1.25rem;
    }
    
    .section-title {
        font-size: 1.125rem;
    }
    
    .article-title {
        font-size: 1rem;
    }
    
    .agreement-nav,
    .agreement-content {
        padding: 1rem;
    }
}

/* 深色模式支持 */
@media (prefers-color-scheme: dark) {
    :root {
        --bg-color: #1a1a1a;
        --card-color: #2d2d2d;
        --text-primary: #ffffff;
        --text-secondary: #cccccc;
        --text-light: #999999;
        --border-color: #404040;
        --divider-color: #404040;
        --hover-overlay: rgba(255, 255, 255, 0.05);
    }
    
    .section {
        background: rgba(255, 255, 255, 0.05);
    }
    
    .note {
        background: linear-gradient(135deg, rgba(255, 149, 0, 0.15), rgba(255, 149, 0, 0.1));
    }
    
    .highlight {
        background: linear-gradient(135deg, rgba(7, 193, 96, 0.15), rgba(7, 193, 96, 0.1));
    }
}

/* 无障碍支持 - 减少动画 */
@media (prefers-reduced-motion: reduce) {
    * {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}