<p>There's an input field below this line:</p>
<input type="text">

body {
  color: white;
  background-color: darkblue;
}

input[type="text"] {
  background-color: darkblue;
  border: none;
  border-bottom: 2px solid;
  border-image: linear-gradient(to left, #b827fc 0%, #2c90fc 25%, #b8fd33 50%, #fec837 75%, #fd1892 100%);
  border-image-slice: 1;
}