<!DOCTYPE html>

<html>
<head>
  <style type="text/css">
    .box {
      height: 200px;
      width: 200px;
      margin: 50px;
      border-radius: 20px;
      border-top-left-radius: 60px;
      border-bottom-right-radius: 40px;
      box-shadow: 230px 0 15px rgba(0, 0, 0, 0.5);
    }
  </style>
</head>
<body>
  <!-- Should be a smooth shadow with no overdrawing artifacts -->
  <div class="box"></div>
</body>
</html>