<div class="container">
  <h1 class="title">Dropdown Menu</h1>
  <ul>
    <li class="dropdown">
      <input type="checkbox" />
      <a href="#" data-toggle="dropdown">First Menu</a>
      <ul class="dropdown-menu">
        <li><a href="#">Home</a></li>
        <li><a href="#">About Us</a></li>
        <li><a href="#">Services</a></li>
        <li><a href="#">Contact</a></li>
      </ul>
    </li>
    <li class="dropdown">
      <input type="checkbox" />
      <a href="#" data-toggle="dropdown">Second Menu</a>
      <ul class="dropdown-menu">
        <li><a href="#">Home</a></li>
        <li><a href="#">About Us</a></li>
        <li><a href="#">Services</a></li>
        <li><a href="#">Contact</a></li>
      </ul>
    </li>
    <li class="dropdown">
      <input type="checkbox" />
      <a href="#" data-toggle="dropdown">Third Menu</a>
      <ul class="dropdown-menu">
        <li><a href="#">Home</a></li>
        <li><a href="#">About Us</a></li>
        <li><a href="#">Services</a></li>
        <li><a href="#">Contact</a></li>
      </ul>
    </li>
  </ul>
</div>

@import "compass/css3";

@import url("https://fonts.googleapis.com/css?family=Lato:300,400,700,900");
@import url(https://fonts.googleapis.com/css?family=Pacifico);

body {
  font-family: "Lato", Helvetica, Arial;
  font-size: 16px;
}

*, *:before, *:after {
  -webkit-border-sizing: border-box;
  -moz-border-sizing: border-box;
  border-sizing: border-box;
}

.container {
  width: 350px;
  margin: 50px auto;
  
  & > ul {
    list-style: none;
    padding: 0;
    margin: 0 0 20px 0;
  }
}

// =============================================================================
//  Mixins and Variables
// =============================================================================

$orange: #C0392B;
$blue: #2980B9;
$gray: #EEE;

@mixin ul-nostyle {
  list-style: none;
  padding: 0;
  margin: 0;
}

@mixin double-shadow($color) {
  @include box-shadow(0 1px 0 lighten($color, 10%) inset, 0 -1px 0 darken($color, 10%) inset);
}

@mixin hover-style($color) {
  &:hover {
    background: lighten($color, 3%);
  }
}

@mixin animation($content) {
  animation: $content;
  -moz-animation: $content;
  -webkit-animation: $content;
}

@mixin keyframes($name) {
  @keyframes #{$name} { @content; }
  @-moz-keyframes #{$name} { @content; }
  @-webkit-keyframes #{$name} { @content; }
}

// =============================================================================
//  Classes
// =============================================================================

.title {
  font-family: 'Pacifico';
  font-weight: norma;
  font-size: 40px;
  text-align: center;
  line-height: 1.4;
  color: $orange;
}

.dropdown {
  position: relative;
  
  a { text-decoration: none; }

  [data-toggle="dropdown"] {
    display: block;
    color: white;
    background: $orange;
    @include double-shadow($orange);
    @include hover-style($orange);
    @include text-shadow(0 -1px 0 rgba(0,0,0,0.3));
    padding: 10px;
    
    &:before {
      position: absolute;
      display: block;
      content: '\25BC';
      font-size: 0.7em;
      color: #fff;
      top: 13px;
      right: 10px;
      @include transform(rotate(0deg));
      @include transition(transform .6s);
    }
  }

  & > .dropdown-menu {
    max-height: 0;
    overflow: hidden;
    @include ul-nostyle;
    @include transform(scaleY(0));
    @include transform-origin(50%, 0%);
    @include transition(max-height .6s ease-out);
    @include animation(hideAnimation .4s ease-out);

    li {
      padding: 0;

      a {
        display: block;
        color: darken($gray, 50%);
        background: $gray;
        @include double-shadow($gray);
        @include hover-style($gray);
        @include text-shadow(0 -1px 0 rgba(255,255,255,0.3));
        padding: 10px 10px;
      }
    }
  }
  
  & > input[type="checkbox"] {
    opacity: 0;
    display: block;
    position: absolute;
    top: 0;
    width: 100%;
    height: 100%;
    cursor: pointer;
    
    &:checked ~ .dropdown-menu {
      max-height: 9999px;
      display: block;
      @include transform(scaleY(1));
      @include animation(showAnimation .5s ease-in-out);
      @include transition(max-height 2s ease-in-out);
    }
    
    &:checked + a[data-toggle="dropdown"] {
      &:before {
        @include transform(rotate(-180deg));
        @include transition(transform .6s);
      }
    }
  }
}

@include keyframes(showAnimation) {
  0% {
    @include transform(scaleY(0.1));
  }
  40% {
    @include transform(scaleY(1.04));
  }
  60% {
    @include transform(scaleY(0.98));
  }
  80% {
    @include transform(scaleY(1.04));
  }
  100% {
    @include transform(scaleY(0.98));
  }       
  80% {
    @include transform(scaleY(1.02));
  }
  100% {
    @include transform(scaleY(1));
  }
}

@include keyframes(hideAnimation) {
  0% {
    @include transform(scaleY(1));
  }
  60% {
    @include transform(scaleY(0.98));
  }
  80% {
    @include transform(scaleY(1.02));
  }
  100% {
    @include transform(scaleY(0));
  }
}