CSS导航菜单：固定当前选中项的下划线宽度与动画控制

.snip1168 li:before {
  top: 0;
  display: inline-block;
  height: 3px;
  width: 0%; /* 初始宽度为0 */
  content: "";
  background-color: black;
}

.snip1168 li:hover:before,
.snip1168 .current a:before { /* 尝试为.current设置100%宽度 */
  opacity: 1;
  width: 100%;
}

.snip1168 li a {
  transition: transform ease 400ms;
  transform: translate(0, 0);
  display: inline-block;
}

.snip1168 li:hover a { /* 悬停时文本移动效果 */
  transition: transform ease 400ms;
  transform: translate(0, -10px);
}

<ul class='snip1168'>
  <li class='current'><a href="#" data-hover="Work">Work</a></li>
  <li><a href="#" data-hover="Recs">Recs</a></li>
  <li><a href="#" data-hover="Say Hi">Say Hi</a></li>
</ul>

<div class='container'>
  <main class='main'>
    <div class='nav'>
      <div class='navIcon'>
        <img src="https://picsum.photos/40" height={40} width={40} />
      </div>
      <ul class='snip1168'>
        <li id='current'><a href="#" data-hover="Work">Work</a></li> <!-- 更改为id='current' -->
        <li><a href="#" data-hover="Recs">Recs</a></li>
        <li><a href="#" data-hover="Say Hi">Say Hi</a></li>
      </ul>
    </div>
  </main>
</div>

/* ... 现有CSS代码 ... */

.snip1168 li:hover:before { /* 移除 .snip1168 .current a:before */
  opacity: 1;
  width: 100%;
}

/* 添加新的规则，针对id为current的li元素下的::before伪元素 */
li#current::before {
  width: 100% !important; /* 强制设置宽度为100% */
}

/* ... 其他CSS代码 ... */

html,
body {
  padding: 0;
  margin: 0;
  font-family: "sequel-sans-roman", -apple-system, BlinkMacSystemFont, Segoe UI, Roboto, Oxygen, Ubuntu, Cantarell, Fira Sans, Droid Sans, Helvetica Neue, sans-serif;
}

.container {
  padding: 0 2rem;
}

.main {
  min-height: 100vh;
  padding: 4rem 0;
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

a {
  color: inherit;
  text-decoration: none;
}

* {
  box-sizing: border-box;
}

.navIcon {
  display: inline-block;
  flex-grow: 1;
}

.nav {
  display: flex;
  justify-content: space-between;
  width: 100%;
  margin-top: 2.4em;
}

.snip1168 {
  text-align: center;
  text-transform: uppercase;
}

.snip1168 * {
  box-sizing: border-box;
}

.snip1168 li {
  display: inline-block;
  list-style: outside none none;
  margin: 0 1.5em;
  padding: 0;
  background: ppink; /* 注意：ppink可能不是有效颜色，此处保留原文 */
}

.snip1168 li {
  padding: 2.4em 0 0.5em;
  color: rgba(0, 0, 0, 1);
  position: relative;
  text-decoration: none;
  background: pink;
  display: inline-block;
}

.snip1168 li:before,
.snip1168 li:after {
  position: absolute;
  -webkit-transition: all 0.35s ease;
  transition: all 0.35s ease;
}

.snip1168 li:before {
  top: 0;
  display: inline-block;
  height: 3px;
  width: 0%;
  content: "";
  background-color: black;
}

.snip1168 li:hover:before { /* 仅处理悬停效果 */
  opacity: 1;
  width: 100%;
}

/* 新增代码：确保id为current的li元素下划线始终为100% */
li#current::before {
  width: 100% !important;
}

.snip1168 li:hover:after,
.snip1168 .current li:after { /* 此处.current li:after可能需要根据实际需求调整 */
  max-width: 100%;
}

.mainText {
  text-transform: uppercase;
  font-size: 1.1rem;
}

.snip1168 li a {
  transition: transform ease 400ms;
  transform: translate(0, 0);
  display: inline-block;
}

.snip1168 li:hover a {
  transition: transform ease 400ms;
  transform: translate(0, -10px);
}