<form class="search">
  <div class="search__wrapper">
    <input type="text" name="" placeholder="Search for..." class="search__field">
    <button type="submit" class="fa fa-search search__icon"></button>
  </div>
</form>

@icon-size: 50px;
@main-color: #e9f1f4;


// STYLE TO WRAP UP THE DEMO
.search {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translateX(-50%) translateY(-50%);
  * {
    outline: none;
    box-sizing: border-box;
  }
}

// SEARCH FIELD
.search__wrapper {
  position: relative;
}
.search__field {
  width: @icon-size;
  height: @icon-size;
  color: transparent;
  font-family: Lato, sans-serif;
  font-size: 1.35em;
  padding: .35em (@icon-size) .35em 0;
  border: 1px solid transparent;
  border-radius: 0;
  cursor: pointer;
  -webkit-transition: all 0.3s ease-in-out;
  transition: all 0.3s ease-in-out;
  &:focus {
    border-bottom-color: #ccc;
    width: 50vw;
    color: #2b2b2b;
    cursor: default;
    ~ .search__icon {
      background-color: transparent;
      cursor: pointer;
      pointer-events: auto;
    }
  }
}
.search__icon {
  position: absolute;
  top: 0;
  right: 0;
  background-color: @main-color;
  width: @icon-size;
  height: @icon-size;
  font-size: 1.35em;
  text-align: center;
  border-color: transparent;
  border-radius: 50%;
  pointer-events: none;
  display: inline-block;
  -webkit-transition: background-color 0.2s ease-in-out;
  transition: background-color 0.2s ease-in-out;
}


// FIELD LABELING
.search__field::-webkit-input-placeholder {
  position: relative;
  top: 0;
  left: 0;
  -webkit-transition-property: top, color;
  transition-property: top, color;
  -webkit-transition-duration: .1s;
  transition-duration: .1s;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  -webkit-perspective: 1000;
  perspective: 1000;
}
.search__field:-moz-placeholder {
  position: relative;
  top: 0;
  left: 0;
  -webkit-transition-property: top, color;
  transition-property: top, color;
  -webkit-transition-duration: .1s;
  transition-duration: .1s;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  -webkit-perspective: 1000;
  perspective: 1000;
}
.search__field::-moz-placeholder {
  position: relative;
  top: 0;
  left: 0;
  -webkit-transition-property: top, color;
  transition-property: top, color;
  -webkit-transition-duration: .1s;
  transition-duration: .1s;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  -webkit-perspective: 1000;
  perspective: 1000;
}
.search__field:-ms-input-placeholder {
  position: relative;
  top: 0;
  left: 0;
  -webkit-transition-property: top, color;
  transition-property: top, color;
  -webkit-transition-duration: .1s;
  transition-duration: .1s;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  -webkit-perspective: 1000;
  perspective: 1000;
}
.search__field::-webkit-input-placeholder[style*=hidden] {
  color: darken(@main-color, 30%);
  font-size: .65em;
  font-weight: normal;
  top: -(round(@icon-size / 2.5));
  opacity: 1;
  visibility: visible !important;
}
.search__field:-moz-placeholder[style*=hidden] {
  color: darken(@main-color, 30%);
  font-size: .65em;
  font-weight: normal;
  top: -(round(@icon-size / 2.5));
  opacity: 1;
  visibility: visible !important;
}
.search__field::-moz-placeholder[style*=hidden] {
  color: darken(@main-color, 30%);
  font-size: .65em;
  font-weight: normal;
  top: -(round(@icon-size / 2.5));
  opacity: 1;
  visibility: visible !important;
}
.search__field:-ms-input-placeholder[style*=hidden] {
  color: darken(@main-color, 30%);
  font-size: .65em;
  font-weight: normal;
  top: -(round(@icon-size / 2.5));
  opacity: 1;
  visibility: visible !important;
}