console 命令行工具 X clear

console

<div></div>

div {
    position: relative;
    margin: 50px auto;
    width: 200px;
    height: 150px;
    background: #000;
}
div::before {
    position: absolute;
    top: -20px;
    left: 80%;
    display: block;
    content: "";
    border: 10px solid transparent;
    border-bottom-color: #000;
}