JSFiddle - React, Tailwind, and code Playground

by Vadim

HTML

<div class="box">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Et dicta, eveniet voluptatibus. Sapiente molestiae aperiam necessitatibus eaque saepe quasi doloribus, libero tenetur! Sint repudiandae atque, adipisci, ipsam impedit ex possimus.</div>

CSS

body {
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.box {
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  padding: 5px;
  background-color: black;
  width: 300px;
  height: 200px;
  border-top-right-radius: 20px;
  border-bottom-right-radius: 20px;
  position: relative;
}

.box::after {
  content: '';
  display: block;
  width: calc(100% - 10px);
  height: 25px;
  background-image: linear-gradient(175deg, black 50%, transparent 50%);
  position: absolute;
  bottom: 0;
  left: 0;
  transform: translateY(100%);
}