Bootstrap 2.3.2 - responsive forms

HTML

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.min.css">
<script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.4.0/css/font-awesome.min.css">
<div class="repeat"></div>

CSS

.repeat {
  width: 100px;
  height: 100px;
  background-image: 
    repeating-linear-gradient(
      180deg,
      blue,
      blue 50px,
      red 50px,
      red 100px /* determines size */
    );
}