利用CSS实现标签自定义属性值悬停提示

<p id="IP08">
  Uneven development is, precisely that: capitalist factors (firms, industries, countries) have a common trait, but
  <span title="capitalist factors (firms, industries, countries)">they</span> show uneven unfolding and cannot be individually predicted.
  Since the factors are mutually and interdependently related, the general trend that we define as the law of uneven development can be inferred from
  <span title="capitalist factors (firms, industries, countries)">their</span> relationship, which has a specific connotation, i.e., the difference in the paces of the factors that make up the relationship itself.
  Since the general trend is determined by capitalism’s nature,
  <span title="the general trend">it</span> cannot change without changing the nature of capitalism itself.
</p>

<p id="IP08">
  Uneven development is, precisely that: capitalist factors (firms, industries, countries) have a common trait, but
  <span ref="capitalist factors (firms, industries, countries)">they</span> show uneven unfolding and cannot be individually predicted.
  Since the factors are mutually and interdependently related, the general trend that we define as the law of uneven development can be inferred from
  <span ref="capitalist factors (firms, industries, countries)">their</span> relationship, which has a specific connotation, i.e., the difference in the paces of the factors that make up the relationship itself.
  Since the general trend is determined by capitalism’s nature,
  <span ref="the general trend">it</span> cannot change without changing the nature of capitalism itself.
</p>

/** Tooltip 样式 **/

/* 确保带有 'ref' 属性的 span 元素具有相对定位，以便其伪元素可以绝对定位 */
span[ref] {
    position: relative;
}

/* 伪元素 '::after' 定义了工具提示的默认（隐藏）样式 */
span[ref]:after {
    content: attr(ref); /* 将 'ref' 属性的值作为内容 */
    background-color: #00adb5; /* 背景颜色 */
    color: #fff; /* 文字颜色 */
    position: absolute; /* 绝对定位 */
    padding: 1px 5px 2px 5px; /* 内边距 */
    top: 100%; /* 定位在 span 元素的下方 */
    left: 0px; /* 从 span 元素的左侧开始 */
    white-space: nowrap; /* 防止内容换行 */
    opacity: 0; /* 初始透明度为0，隐藏 */
    box-shadow: 3px 3px 5px #00ADB5; /* 阴影效果 */
    border: 1px solid rgb(197, 195, 195); /* 边框 */
    border-radius: 0 5px 0 5px; /* 边框圆角 */
    visibility: hidden; /* 初始可见性为隐藏 */
    z-index: 20; /* 确保工具提示位于其他内容之上 */
}

/* 当鼠标悬停在 'span[ref]' 上时，改变伪元素 '::after' 的样式，使其可见 */
span[ref]:hover:after {
    opacity: 1; /* 透明度变为1，显示 */
    transition: all 0.1s ease .5s; /* 添加过渡效果，延迟0.5秒后开始 */
    visibility: visible; /* 设置为可见 */
    /* 可以选择性添加动画，如下面的 @keyframes grow */
    /* animation: grow 3s forwards; */
}

/* 可选：动画效果，如果不需要可以忽略 */
@keyframes grow {
    0% {
        transform: scale(0);
    }
    30%, 65% {
        transform: scale(1);
    }
    70%, 100% {
        transform: scale(0);
    }
}

<span data-ref="capitalist factors (firms, industries, countries)">they</span>