JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>simple</title>
</head>
<body>
 <div class="holder">
 <div class="title">
   <h1>Login / Sign up</h1>
   </div>
   <div class="form">
     <form action="">
       <input type="text" placeholder="username">
     </form>
   </div>
 </div> 
</body>
</html>

CSS

*{
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}
body{
  width: 100%;
  height: 100vh;
  background: #ccc;
}
.holder *{
  margin: 0.2em;
}
.holder{
  width: 50%;
  background: white;
  height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0.8em;
  border-radius: 0% 15% 15% 0%;
}
.title{
  text-align: center;
  font-weight: bold;
}