Create a text field for a single line of text.

<html>
<head><style>body {min-height: 300px;} input { font-size: 16px; } textarea { font-size: 16px; } </style></head>
<body>
  <input type="text" placeholder="Say something">
  <button>Send</button>
</body>
</html>]]>

Make sure to select input.