body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f5f5f5;
    color: #333;
    line-height: 1.6;
}

header {
    background-color: #007bff;
    color: white;
    text-align: center;
    padding: 20px;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
}

header h1 {
    margin: 0;
    font-size: 2em;
}

header p {
    margin: 5px 0 0;
    opacity: 0.9;
}

main {
    max-width: 1200px;
    margin: 20px auto;
    padding: 0 20px;
}

#nav-container {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

details {
    background: white;
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    overflow: hidden;
}

summary {
    padding: 15px 20px;
    font-weight: bold;
    cursor: pointer;
    background-color: #e9ecef;
    transition: background-color 0.3s;
    list-style: none; /* 隐藏默认箭头 */
    position: relative;
}

summary::-webkit-details-marker {
    display: none; /* 隐藏Chrome箭头 */
}

summary::before {
    content: '+';
    position: absolute;
    right: 20px;
    font-weight: bold;
}

details[open] summary::before {
    content: '−';
}

summary:hover {
    background-color: #dee2e6;
}

ul {
    margin: 0;
    padding: 0 0 0 20px;
    list-style: none;
}

li a {
    display: block;
    padding: 10px 15px;
    color: #007bff;
    text-decoration: none;
    border-bottom: 1px solid #f8f9fa;
    transition: background-color 0.3s;
}

li a:hover {
    background-color: #f8f9fa;
    color: #0056b3;
}

li:last-child a {
    border-bottom: none;
}

footer {
    text-align: center;
    padding: 20px;
    background-color: #007bff;
    color: white;
    margin-top: 40px;
}

/* 移动图片动画 */
@keyframes moveLeftRight {
  0% {
    transform: translateX(-50px); /* 从左偏移开始 */
  }
  50% {
    transform: translateX(50px);  /* 到右偏移 */
  }
  100% {
    transform: translateX(-50px); /* 回左偏移 */
  }
}

.moving-image-container {
  position: fixed;              /* 固定在视口底部 */
  bottom: 20px;                 /* 距离底部20px，可调整 */
  left: 50%;                    /* 水平居中 */
  transform: translateX(-50%);  /* 初始居中 */
  z-index: 999;                 /* 确保在最上层 */
  animation: moveLeftRight 5s ease-in-out infinite; /* 5秒周期，缓动，无限循环 */
  opacity: 0.8;                 /* 半透明，可调整 */
}

.moving-image-container img {
  display: block;               /* 移除多余间距 */
  border-radius: 10px;          /* 可选：圆角 */
  box-shadow: 0 4px 8px rgba(0,0,0,0.2); /* 可选：阴影 */
}

/* 响应式：移动端 */
@media (max-width: 768px) {
    header h1 { font-size: 1.5em; }
    summary { padding: 12px 15px; font-size: 14px; }
    li a { padding: 8px 10px; font-size: 14px; }
    .moving-image-container img {
      width: 150px;               /* 移动端缩小图片宽度 */
    }
}