/* 整体样式设定 */
body {
    margin: 0;
    padding: 0;
    font-family: 'Roboto', sans-serif; /* 使用现代无衬线字体，确保可读性 */
    background-color: #ffffff; /* 纯白色背景 */
    color: #333333; /* 主要文字颜色为深灰，提升可读性 */
}

/* 导航栏样式 */
.navbar {
    position: fixed; /* 固定在顶部 */
    top: 0;
    width: 100%;
    background: linear-gradient(90deg, #0f2027, #2c5364); /* 渐变背景色，主色调深蓝到蓝绿色 */
    padding: 15px 30px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1); /* 轻微阴影，增加层次感 */
    z-index: 1000;
}
.navbar a {
    color: #ffffff;
    text-decoration: none;
    margin: 0 15px;
    font-size: 16px;
    transition: color 0.3s ease;
}
.navbar a:hover {
    color: #1abc9c; /* 点缀色高亮 */
}

/* 章节导航系统 */
.section-nav {
    position: fixed;
    top: 80px;
    right: 30px;
    background: rgba(0, 0, 0, 0.05);
    padding: 10px;
    border-radius: 8px;
}
.section-nav a {
    display: block;
    color: #333333;
    text-decoration: none;
    margin: 5px 0;
    font-size: 14px;
    transition: color 0.3s ease;
}
.section-nav a:hover {
    color: #1abc9c;
}

/* 主内容区块 */
.section {
    padding: 100px 30px 60px 30px; /* 上内边距留出导航栏空间 */
    max-width: 1200px;
    margin: 0 auto;
}
.section h2 {
    font-size: 24px;
    margin-bottom: 20px;
    color: #0f2027; /* 主色调标题 */
    position: relative;
}
.section h2::after {
    content: '';
    display: block;
    width: 50px;
    height: 3px;
    background: #1abc9c; /* 点缀色线条 */
    margin-top: 10px;
    border-radius: 2px;
}
.section p {
    font-size: 16px;
    line-height: 1.6;
    margin-bottom: 20px;
    color: #555555;
}
.section img {
    width: 100%;
    max-width: 320px;
    border-radius: 12px; /* 圆角效果 */
    box-shadow: 0 4px 8px rgba(0,0,0,0.1); /* 阴影效果 */
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.section img:hover {
    transform: scale(1.05); /* 悬浮放大效果 */
    box-shadow: 0 8px 16px rgba(0,0,0,0.2); /* 加深阴影 */
}

/* 背景分隔线 */
.divider {
    height: 2px;
    background: linear-gradient(90deg, rgba(0,0,0,0), rgba(0,0,0,0.1), rgba(0,0,0,0));
    margin: 40px 0;
}

/* 按钮样式 */
.button {
    display: inline-block;
    padding: 10px 25px;
    background-color: #2c5364;
    color: #ffffff;
    text-decoration: none;
    border-radius: 5px;
    transition: background-color 0.3s ease, transform 0.3s ease;
}
.button:hover {
    background-color: #1abc9c;
    transform: translateY(-3px);
}

/* 弹出提示样式 */
.tooltip {
    position: relative;
    display: inline-block;
}
.tooltip .tooltiptext {
    visibility: hidden;
    width: 200px;
    background-color: #1abc9c;
    color: #ffffff;
    text-align: center;
    border-radius: 6px;
    padding: 10px;
    position: absolute;
    z-index: 1;
    bottom: 125%; /* 显示在上方 */
    left: 50%;
    margin-left: -100px;
    opacity: 0;
    transition: opacity 0.3s;
}
.tooltip:hover .tooltiptext {
    visibility: visible;
    opacity: 1;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .navbar {
        padding: 10px 20px;
    }
    .navbar a {
        margin: 0 10px;
        font-size: 14px;
    }
    .section {
        padding: 80px 20px 40px 20px;
    }
    .section h2 {
        font-size: 20px;
    }
    .section p {
        font-size: 14px;
    }
}
@media (max-width: 480px) {
    .navbar {
        padding: 8px 15px;
    }
    .navbar a {
        margin: 0 5px;
        font-size: 12px;
    }
    .section h2 {
        font-size: 18px;
    }
    .section p {
        font-size: 13px;
    }
    .button {
        padding: 8px 20px;
        font-size: 14px;
    }
}

/* 动画效果 */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}
.fade-in {
    animation: fadeIn 1s ease-out forwards;
}

/* 页面提示样式 */
.page-alert {
    background-color: #fffae6;
    border-left: 6px solid #ffecb3;
    padding: 15px;
    margin: 20px 0;
    font-size: 16px;
    color: #665c00;
    border-radius: 4px;
}

/* 图表样式 */
.chart {
    width: 100%;
    height: 400px;
    background: #f5f5f5;
    border-radius: 8px;
    position: relative;
    overflow: hidden;
    transition: transform 0.5s ease;
}
.chart:hover {
    transform: rotateY(360deg);
}
.chart::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, #2c5364, #203a43, #0f2027);
    opacity: 0.8;
    transform: scale(1.1);
}

/* 卡片样式 */
.card {
    background: #ffffff;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
    padding: 20px;
    margin: 20px 0;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 12px rgba(0,0,0,0.2);
}

/* 列表样式 */
ul.custom-list {
    list-style: none;
    padding: 0;
}
ul.custom-list li {
    background: #e0f7fa;
    margin: 10px 0;
    padding: 10px;
    border-radius: 5px;
    position: relative;
}
ul.custom-list li::before {
    content: '✔';
    position: absolute;
    left: 10px;
    color: #1abc9c;
}
ul.custom-list li span {
    margin-left: 25px;
}