CSS3实现动态背景登录框的代码

<div class="htmleaf-container">    <div class="wrapper">      <div class="container">        <h1>Welcome</h1>        <form class="form">          <input type="text" placeholder="Username">          <input type="password" placeholder="Password">          <button type="submit" id="login-button">Login</button>        </form>      </div>      <ul class="bg-bubbles">        <li></li>        <li></li>        <li></li>        <li></li>        <li></li>        <li></li>        <li></li>        <li></li>        <li></li>        <li></li>      </ul>    </div>  </div>  <script src="js/jquery-2.1.1.min.js" type="text/javascript"></script>  <script>    $('#login-button').click(function (event) {      event.preventDefault();      $('form').fadeOut(500);      $('.wrapper').addClass('form-success');    });  </script>