Flat HTML5/CSS3 Login Form

 HML CODE 

<div class="login-page">

  <div class="form">

    <form class="register-form">

      <input type="text" placeholder="name"/>

      <input type="password" placeholder="password"/>

      <input type="text" placeholder="email address"/>

      <button>create</button>

      <p class="message">Already registered? <a href="#">Sign In</a></p>

    </form>

    <form class="login-form">

      <input type="text" placeholder="username"/>

      <input type="password" placeholder="password"/>

      <button>login</button>

      <p class="message">Not registered? <a href="#">Create an account</a></p>

    </form>

  </div>

</div>

CSS CODE

@import url(https://fonts.googleapis.com/css?family=Roboto:300);

.login-page {

  width: 360px;

  padding: 8% 0 0;

  margin: auto;

}

.form {

  position: relative;

  z-index: 1;

  background: #FFFFFF;

  max-width: 360px;

  margin: 0 auto 100px;

  padding: 45px;

  text-align: center;

  box-shadow: 0 0 20px 0 rgba(0, 0, 0, 0.2), 0 5px 5px 0 rgba(0, 0, 0, 0.24);

}

.form input {

  font-family: "Roboto", sans-serif;

  outline: 0;

  background: #f2f2f2;

  width: 100%;

  border: 0;

  margin: 0 0 15px;

  padding: 15px;

  box-sizing: border-box;

  font-size: 14px;

}

.form button {

  font-family: "Roboto", sans-serif;

  text-transform: uppercase;

  outline: 0;

  background: #4CAF50;

  width: 100%;

  border: 0;

  padding: 15px;

  color: #FFFFFF;

  font-size: 14px;

  -webkit-transition: all 0.3 ease;

  transition: all 0.3 ease;

  cursor: pointer;

}

.form button:hover,.form button:active,.form button:focus {

  background: #43A047;

}

.form .message {

  margin: 15px 0 0;

  color: #b3b3b3;

  font-size: 12px;

}

.form .message a {

  color: #4CAF50;

  text-decoration: none;

}

.form .register-form {

  display: none;

}

.container {

  position: relative;

  z-index: 1;

  max-width: 300px;

  margin: 0 auto;

}

.container:before, .container:after {

  content: "";

  display: block;

  clear: both;

}

.container .info {

  margin: 50px auto;

  text-align: center;

}

.container .info h1 {

  margin: 0 0 15px;

  padding: 0;

  font-size: 36px;

  font-weight: 300;

  color: #1a1a1a;

}

.container .info span {

  color: #4d4d4d;

  font-size: 12px;

}

.container .info span a {

  color: #000000;

  text-decoration: none;

}

.container .info span .fa {

  color: #EF3B3A;

}

body {

  background: #76b852; /* fallback for old browsers */

  background: rgb(141,194,111);

  background: linear-gradient(90deg, rgba(141,194,111,1) 0%, rgba(118,184,82,1) 50%);

  font-family: "Roboto", sans-serif;

  -webkit-font-smoothing: antialiased;

  -moz-osx-font-smoothing: grayscale;      

}

JS CODE 

$('.message a').click(function(){

   $('form').animate({height: "toggle", opacity: "toggle"}, "slow");

});