Flat responsive form using CSS3 & HTML5 by Rex Kirby

<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>
</div>

@import url(https://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%;
  resize: vertical;
}

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: 0.3s ease;
  -moz-transition: 0.3s ease;
  -o-transition: 0.3s ease;
  -ms-transition: 0.3s ease;
  transition: 0.3s 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%;
  }
}