<div class="background"></div>

<form>
  <h3>Login</h3>
  <input type="text" placeholder="Username"/> 
  <input type="password" placeholder="********" />
  
  <button>Enter</button>
</form>  


<aside>
  <h3>Mail</h3>
  <ul>
    <li class="active">Compose</li>
    <li>Inbox <span>14</span></li>
    <li>Draft</li>
    <li>Sent</li>
    <li>Trash</li>
    <li>Junk Mail</li>
  </ul>
</aside> 



<div class="email-details">
  <div><label for="">To:</label><input type="text" /></div>
  <div>
  <label for="">Subject:</label><input type="text" />
  </div>
</div>

<section>
  <ul>
    <li class="icon-bold"></li>
    <li class="icon-italic"></li>
    <li class="icon-underline"></li> 
    <li class="icon-paste"></li>
    <li class="icon-paper-clip"></li>
    
  </ul>
  
  <textarea></textarea> 
  
  <button>Send</button>
</section>





<svg>
  <filter id="blur">
    <feGaussianBlur stdDeviation="10"/>
  </filter>
</svg>
@import "compass/css3";

$site-color: #8e44ad;
 
html {
  font-family: 'Noto Sans', sans-serif;
  height: 100%;
  overflow-x: hidden;
}
 
* {
  @include box-sizing(border-box); 
}

h3 { 
  color: rgba(white,0.99);
  font-family: 'Lobster', cursive;
  font-size: 5em;
  margin: 0.5em;
  text-align: center;
  text-shadow: 2px 2px rgba(black,0.8);
  @include rotate(-12deg);
  -webkit-font-smoothing: subpixel-antialiased;
} 

// Uses a small background which is streched ad blurred, which keeps page weight down.

.background {
  background: url( 'https://s.cdpn.io/31787/city.jpg'); 
  background-size: cover;
  -webkit-filter:  blur(10px);
  filter: url(#blur);
  height: 105%;
  position: absolute;
  width: 105%;
  right: -2.5%;
  left: -2.5%;
  top: -2.5%;
  bottom: -2.5%;
  z-index: -1;
}


// @extendables
%box {
 background: rgba(black,0.5);
  box-shadow: inset 0 0 0 1em rgba(black, 0.6), 0 3px 4px -1px rgba(black,0.4);
  border: 0.5em solid rgba(white, 0.4);
  border-radius: 1em; 
  transform: translateZ(0);
}
 
%button {
   background: rgba($site-color,0.8);
    border: 0;
    color: #fff;
    font-size: 1.3em;
    height: 3em;
  
      &:hover {
        background: $site-color ; 
        
      }
}
  
// login form 

form {
  @extend %box;
  height: 30em; 
  left: 50%;
  margin-left: -11em;
  margin-top: 8em;
  position: absolute;
  width: 22em; 
  

  
  input {
    border: 0;
    margin: 0.3em;
    margin-left: 10%;
    padding: 0.4em;
    font-size: 1.5em;
    width: 80%; 
  }
  
  button {
   @extend %button;
    margin-left: 10%;
    margin-top: 1.5em;
    width: 80%; 
    

  }
}


// aside menu

aside {
  background: rgba(black,0.4);
  height: 100%; 
  left: -30%; 
  opacity: 0;
  position: absolute;
  width:25%;


ul {
  list-style: none;
  margin: 0;
  padding: 0;
  width: 100%;
  
  
  li {
    @include background-image(linear-gradient(top,  rgba(black,0.4) 0%,rgba(black,0.5) 100%));    
    border-left: 0.6em solid rgba(white,0.6);
    box-shadow: inset 0 1px 2px rgba(255, 255, 255, 0.2), inset 0 -1px 2px rgba(0, 0, 0, 0.2);
    color: rgba(255, 255, 255, 0.9);
    cursor: pointer;
    font-family: 'Noto Sans', sans-serif;
    font-size: 1.2em;
    height: 3em;
    line-height: 2.8; 
    padding-left: 1em;
    position: relative;
    text-shadow: 1px 1px 4px rgba(black, 0.3),-1px -1px 4px rgba(white, 0.1);
    transition: border 0.4s ease-in-out, background-image 0.4s ease-in-out;
    width: 100%;
    &:hover {
            @include background-image(linear-gradient(top,  rgba(black,0.8) 0%,rgba(black,0.9) 100%));
        border-left: 0.6em solid rgba(white, 0.99);
      }
      
      span {
        background: $site-color;
       float: right;
        line-height: 2;
        margin-right: 1em;
        margin-top: 0.4em;
        height: 2em;
        text-align: center;
        width: 2em;
      }
  }
  
  .active {
    border-left: 0.6em solid rgba($site-color,0.8);
    transition: border 0.4s ease-in-out, background-image 0.4s ease-in-out;
    &:hover {
        @include background-image(linear-gradient(top,  rgba(black,0.8) 0%,rgba(black,0.9) 100%));
        border-left: 0.6em solid $site-color;
      }
  }
} 
}

// subject and to box

.email-details {
 @extend %box;
  height: 9em;
    opacity: 0;
  padding-top: 1.2em;
  position: absolute;
  right: 5%;
  top: -10em;
  width: 65%;
  
  label {
    background: rgba(black,0.6);
    color: #fff;
    float: left;
   height: 2em;
    line-height: 2.1;
    margin: 0.4em;
    margin-left: 5%;
    margin-right: 0;
    padding-left: 1em;
    width: 20%;
  }
  
  input {
    float: right;
   height: 2em; 
    margin: 0.4em;
    margin-right: 5%;
    margin-left: 0;
    width: 70%;
  }
}


// main body of email

section {
 @extend %box; 
  min-height: 30em; 
  max-width: 60em;
    opacity: 0;
  position: absolute;
  right: -70%;
  top: 11.2em;
  width: 65%;
  
  [class*="icon-"] {
   color: #fff;
    cursor: pointer;
    float: left;
    font-size: 1.5em;
    height: 1.5em;
    line-height: 1.4;
        margin: 0.4em;
    margin-left: 0;
    text-align: center;
    transition: 0.4s border ease-in-out,0.4s color ease-in-out;
        width: 1.5em;
    
    &:hover {
     border-color: $site-color; 
      color: $site-color;
    }
  }
  
  ul {
    
  li {
   background: rgba(black,0.7);
    border: 2px solid rgba(white, 0.6);
    border-radius: 0.3em;
  }
  }
  textarea {
    height: 18em;
    margin-left: 5%;
    position: relative;
   width: 90%; 
  }
  
  button {
   @extend %button;
    float: right;
    margin-bottom: 1.6em;
    margin-right: 5%;
    margin-top: 0.6em;
    width: 30%;
  }
}





// animation classes 
.complete {
  animation: 1s fadeout ease-out; 
  animation-fill-mode: forwards; 
  opacity: 0;
  transform: scale(2);
}

.subject-slide {
    animation: 0.5s subject-slide ease-out;
  animation-delay: 1.5s;
  animation-fill-mode: backwards; 
  opacity: 1;
  top: 1.5em;
}

.aside-slide {
  animation: 0.5s aside-slide ease-out;
  animation-delay: 1s;
  animation-fill-mode: backwards; 
  opacity: 1;
  left: 0;
}

.section-slide {
  animation: 1s section-slide ease-out;
  animation-delay: 2s; 
  animation-fill-mode: backwards;
  opacity: 1;
  right: 5%; 
}

//animation keyframes

@keyframes subject-slide {
  0% {
    top: -10em; 
  }
  
  100% {
    top: 1.5em;
  }
}


@keyframes aside-slide {
  0% {
    left: -30%; 
  }
  
  100% {
    left: 0;
  }
}

@keyframes section-slide {
  0% {
    right: -70%; 
  }
  
  100% {
    right: 5%;
  }
}



@keyframes fadeout {
  0% {
    opacity: 1;
    transform: scale(1); 
  }
  
  100% {
    opacity: 0;
    transform: scale(2);
  }
}
$("button").click(function() {
  $("form").addClass('complete');
  $(".email-details").addClass('subject-slide');
  $("section").addClass('section-slide');
  $("aside").addClass('aside-slide');
});

External CSS

  1. https://netdna.bootstrapcdn.com/font-awesome/3.2.1/css/font-awesome.min.css
  2. https://fonts.googleapis.com/css?family=Lobster|Noto+Sans:400,700

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js