SOURCE

console 命令行工具 X clear

                    
>
console
<ul>
  <li>HTML</li>
  <li>CSS</li>
  <li>JavaScript</li>
</ul>
ul {
  list-style: none;
}
li {
  margin: 0 10px;
  padding: 0 5px;
  position: relative;
}
li::before {
  position: absolute;
  left: -10px;
  top: 50%;
  margin-top: -.125em;
  content: "";
  width: .25em;
  height: .25em;
  background-color: #ddd;
  transition: all .3s linear;
}
li:hover::before {
  background-color: #000;
}