%ul.slideshow
  %li
    %h3 The Seasons
    <!-- By Keven Law from Los Angeles, USA (Long Hot Summer......) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons, http://commons.wikimedia.org/wiki/File%3AFlickr_-_law_keven_-_Long_Hot_Summer.......jpg -->
    %span Summer

  %li
    <!-- By http://www.ForestWander.com [CC-BY-SA-3.0-us (http://creativecommons.org/licenses/by-sa/3.0/us/deed.en)], via Wikimedia Commons, http://commons.wikimedia.org/wiki/File%3ARed-fall-tree-lake_-_West_Virginia_-_ForestWander.png -->
    %span Fall        

  %li
    <!-- By Valerii Tkachenko [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons, http://commons.wikimedia.org/wiki/File%3AWinter_wonderland_Austria_mountain_landscape_(8290712092).jpg -->
    %span Winter

  %li
    <!-- By Arman7 (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons, http://commons.wikimedia.org/wiki/File%3ABoroujerd_spring.jpg --> 
    %span Spring

@import "bourbon";

html {
  min-height: 100%;
}

body {
  height: 100%;
}

// length of each slide in seconds
$animation-delay: 6s;

.slideshow {
  list-style: none;
  z-index: 1;
  li {
    span { 
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0px;
      left: 0px;
      color: transparent;
      background-size: cover;
      background-position: 50% 50%;
      background-repeat: none;
      opacity: 0;
      z-index: 0;
      -webkit-backface-visibility: hidden;
      backface-visibility: hidden;
      // multiply slide duration by the total number of slides
      @include animation(imageAnimation $animation-delay * 4 linear infinite 0s);
    }
    h3 {
      position: absolute;
      text-align: center;
      z-index: 2;
      bottom: 150px;
      left: 0;
      right: 0;
      opacity: 0;
      font-size: em(65px);
      font-family: 'Josefin Sans', sans-serif;
      text-transform: uppercase;
      color: #fff;
      // multiply slide duration by the total number of slides
      @include animation(titleAnimation $animation-delay * 4 linear 1 0s);

      @media only screen and (min-width: 768px) {
        bottom: 30px;
        font-size: em(130px);
      }

      @media only screen and (min-width: 1024px) {
        font-size: em(175px);
      }
    }
  }
}

// add and remove new slides here, maintaning the animation-delay format
.slideshow li:nth-child(1) span { 
  background-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/203277/summer-slide.jpg);
}
.slideshow li:nth-child(2) span { 
  background-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/203277/fall-slide.jpg);
  @include animation-delay($animation-delay);
}
.slideshow li:nth-child(3) span { 
  background-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/203277/winter-slide.jpg);
  @include animation-delay($animation-delay * 2);
}
.slideshow li:nth-child(4) span { 
  background-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/203277/spring-slide.jpg);
  @include animation-delay($animation-delay * 3);
}

// animation for the slideshow images
@include keyframes(imageAnimation) {
  0% {
    opacity: 0;
    @include animation-timing-function(ease-in);
  }
  12.5% {
    opacity: 1;
    @include animation-timing-function(ease-out);
  }
  25% {
    opacity: 1;
  }
  37.5% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}

// animation for the title
@include keyframes(titleAnimation) {
  0% {
    opacity: 0;
  }
  12.5% {
    opacity: 1;
  }
  25% {
    opacity: 1;
  }
  37.5% {
    opacity: 0;
  }
  100% {
    opacity: 0;
  }
}

// modernizr is used to show the first slide as a fallback for when css animations are not supported
.no-cssanimations .slideshow li span {
  opacity: 1;
}