JSFiddle - React, Tailwind, and code Playground

by infous

HTML

<button>test</button>

CSS

button {
    border: 1px solid red;
    border-radius: 0;
    background: none;
    position: relative;
    font-size: 30px;
    padding: 20px;
    margin: 0 20px;
}

button:before,
button:after {
    background: red;
    content: ' ';
    display: block;
    position: absolute;
    width: 20px;
    top: 0;
    right: 100%;
    height: 100%;
}

button:after {
    background: blue;
    right: auto;
    left: 100%;
}