Flat Responsive Form using CSS3 & HTML5

CSS

@import url(http://fonts.googleapis.com/css?family=Montserrat:400,700);
html{    background:url(http://thekitemap.com/images/feedback-img.jpg) no-repeat;
  background-size: cover;
  height:100%;
}
#feedback-page{
text-align:center;
}
#form-main{
width:100%;
float:left;
padding-top:0px;
}
#form-div {
background-color:rgba(72,72,72,0.4);
padding-left:35px;
padding-right:35px;
padding-top:35px;
padding-bottom:50px;
width: 450px;
float: left;
left: 50%;
position: absolute;
  margin-top:30px;
margin-left: -260px;
  -moz-border-radius: 7px;
  -webkit-border-radius: 7px;
}
.feedback-input {
color:#3c3c3c;
font-family: Helvetica, Arial, sans-serif;
  font-weight:500;
font-size: 18px;
border-radius: 0;
line-height: 22px;
background-color: #fbfbfb;
padding: 13px 13px 13px 54px;
margin-bottom: 10px;
width:100%;
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
-ms-box-sizing: border-box;
box-sizing: border-box;
  border: 3px solid rgba(0,0,0,0);
}
.feedback-input:focus{
background: #fff;
box-shadow: 0;
border: 3px solid #3498db;
color: #3498db;
outline: none;
  padding: 13px 13px 13px 54px;
}
.focused{
color:#30aed6;
border:#30aed6 solid 3px;
}
/* Icons ---------------------------------- */
#name{
background-image: url(http://rexkirby.com/kirbyandson/images/name.svg);
background-size: 30px 30px;
background-position: 11px 8px;
background-repeat: no-repeat;
}
#name:focus{
background-image: url(http://rexkirby.com/kirbyandson/images/name.svg);
background-size: 30px 30px;
background-position: 8px 5px;
  background-position: 11px 8px;
background-repeat: no-repeat;
}
#email{
background-image: url(http://rexkirby.com/kirbyandson/images/email.svg);
background-size: 30px 30px;
background-position: 11px 8px;
background-repeat: no-repeat;
}
#email:focus{
background-image: url(http://rexkirby.com/kirbyandson/images/email.svg);
background-size: 30px 30px;
  background-position: 11px 8px;
background-repeat: no-repeat;
}
#comment{
background-image: url(http://rexkirby.com/kirbyandson/images/comment.svg);
background-size: 30px 30px;
background-position: 11px 8px;
background-repeat: no-repeat;
}
textarea {
width: 100%;
height: 150px;
line-height: 150%;
}
input:hover, textarea:hover,
input:focus, textarea:focus {
background-color:white;
}
#button-blue{
font-family: 'Montserrat', Arial, Helvetica, sans-serif;
float:left;
width: 100%;
border: #fbfbfb solid 4px;
cursor:pointer;
background-color: #3498db;
color:white;
font-size:24px;
padding-top:22px;
padding-bottom:22px;
-webkit-transition: all 0.3s;
-moz-transition: all 0.3s;
transition: all 0.3s;
  margin-top:-4px;
  font-weight:700;
}
#button-blue:hover{
background-color: rgba(0,0,0,0);
color: #0493bd;
}
.submit:hover {
color: #3498db;
}
.ease {
width: 0px;
height: 74px;
background-color: #fbfbfb;
-webkit-transition: .3s ease;
-moz-transition: .3s ease;
-o-transition: .3s ease;
-ms-transition: .3s ease;
transition: .3s ease;
}
.submit:hover .ease{
  width:100%;
  background-color:white;
}
@media only screen and (max-width: 580px) {
#form-div{
left: 3%;
margin-right: 3%;
width: 88%;
margin-left: 0;
padding-left: 3%;
padding-right: 3%;
}
}

HTML

<div id="form-main">
  <div id="form-div">
    <form class="form" id="form1">
     
      <p class="name">
        <input name="name" type="text" class="validate[required,custom[onlyLetter],length[0,100]] feedback-input" placeholder="Name" id="name" />
      </p>
     
      <p class="email">
        <input name="email" type="text" class="validate[required,custom[email]] feedback-input" id="email" placeholder="Email" />
      </p>
     
      <p class="text">
        <textarea name="text" class="validate[required,length[6,300]] feedback-input" id="comment" placeholder="Comment"></textarea>
      </p>
     
     
      <div class="submit">
        <input type="submit" value="SEND" id="button-blue"/>
        <div class="ease"></div>
      </div>
    </form>
  </div>