<div class="body-container">
  <h1>Search bar</h1>
  <div class="search-bar">
    <span class="search-icon"></span>
    <form class="search" action="">
      <input class="search" type="text" placeholder="Search"/>
      <button type="submit" class="btn">Go</button>
    </form>
  </div>
</div>

// Colors
$color_main: #ccf;
$color_background: navy;

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

div.search-bar {
  display: flex;
}

form.search {
  display: inline-flex;
  max-width: 0;
  overflow: hidden;
  transition: 0.5s ease all;
  &.open {
    max-width: 40em;
  }
}

input.search {
  margin: 0 0.4em;
  border: none;
  background: none;
  border-bottom: 1px solid $color_main;
  color: inherit;
  font-family: inherit;
  font-size: 1.5em;
  min-width: 10em;
  width: 70vw;
  max-width: 20em;
  &:focus {
    outline: none;
  }
}

.btn {
  display: inline-block;
  background: none;
  color: $color_main;
  border: 1px solid $color_main;
  border-radius: 0.25em;
  font-size: 1.2em;
  min-width: 3em;
  &:focus {
    outline: none;
    color: $color_background;
    background: $color_main;
  }
}

span.search-icon {
  display: inline-block;
  position: relative;
  width: 2em;
  height: 2em;
  cursor: pointer;
  &:after {
    content: '';
    display: inline-block;
    position: absolute;
    width: 50%;
    height: 50%;
    border-radius: 50%;
    top: 0;
    right: 0;
    border: 0.25em solid $color_main;
  }
  &:before {
    content: '';
    display: inline-block;
    position: absolute;
    height: 0.25em;
    width: 42%;
    background: $color_main;
    top: 50%;
    transform-origin: 100% 50%;
    transform: rotateZ(-45deg);
  }
}

// Stuff here is for centering
div.body-container {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
}

body {
  margin: 0;
  color: $color_main;
  background: $color_background;
  font-family: 'Roboto', sans-serif;
}

var icon = $('.search-icon');
var form = $('form.search');

icon.click(function() {
  form.toggleClass('open');
  if (form.hasClass('open')) {
    form.children('input.search').focus();
  }
});