JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="utf-8" />
        <title>Hello</title>
        <style>
        body{
                margin: 20px;
        }

        .box:after {
                content: "";
                position: absolute;
                top: 0px;
                right: 0px;
                border-width: 20px 20px 0 0;
                border-style: solid;
                border-color: #fff transparent;
                display: block;
                width: 0;
        }

        .box {
                color: #fff;
                background-color: #bbd0ed;
                position: relative;
                height: 80px;
                width: 150px;
                padding: 10px;
        }
        </style>
    </head>
    <body>
        <p class="box">
                Hello!
        </p>
    </body>
</html>