$base-color: #bada55;
$tiles: 13;
$tiles-per-row: 5;
$rows: ceil($tiles / $tiles-per-row);

.tiles {
  @extend .cf;
  position: relative;
  top: 0;
  height: 0;
  padding-bottom: #{100 / $tiles + '%'};
  transition: all 0.3s ease-in-out 1s;
  
  .tile {
    position: absolute;
    top: 0;
    width: #{100 / $tiles + '%'};
    height: 0;
    padding-bottom: #{100 / $tiles + '%'};
    background: darken($base-color, 10%);
    overflow: hidden;
  
    @for $i from 1 to ($tiles + 1) {
      &:nth-child(#{$i}) {
        $color: 128 / $i;
        left: #{($i - 1) * (100 / $tiles) + '%'};
        background: rgb($color, $color, $color);
        transition: all 0.3s ease-in-out #{(($i - 1) * 10 / $tiles) / 10 + 's'};
      }
    }
  }

  &.big {
    padding-bottom: #{(100 / $tiles-per-row) * $rows + '%'};
    transition: all 0.3s ease-in-out;
    
    & .tile {
      width: #{100 / $tiles-per-row + '%'};
      padding-bottom: #{100 / $tiles-per-row + '%'};
    
      @for $i from 1 to ($tiles + 1) {
        &:nth-child(#{$i}) {
          $row: ceil($i / $tiles-per-row);
          left: #{($i - 1 - (($row - 1) * $tiles-per-row)) * (100 / $tiles-per-row) + '%'};
          top: #{($row - 1) * 100 / ($rows) + '%'};
          transition: all 0.3s ease-in-out #{(10 - $i * 10 / $tiles) / 10 + 's'};
        }
      }
    }
  }
}

.content {
  position: relative;
}

.video-wrapper {
  position: relative;
  width: 100%;
  height: 0;
  padding-bottom: 56.25%;
  overflow: hidden;
  transition: padding-bottom 1s ease-in-out;
  
  .hide-video & {
    padding-bottom: 0;
  }
  
  .video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: lighten($base-color, 10%);
  }
}

.play-button {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 3em;
  border: 0.125em solid currentColor;
  border-radius: 5em;
  font-size: 3em;
  line-height: 2.75;
  color: lighten($base-color, 25%);
  text-align: center;
  transform: translate(-50%, -50%);
}


/** GLOBAL STYLES **/
@import url(http://fonts.lug.ustc.edu.cn/css?family=Open+Sans:300|Oswald:400,700,300);

* {
  box-sizing: border-box;
}

html, body { width: 100%; height: 100%; }

html { font-size: 62.5%; }

body {
  background: $base-color;
  font-family: 'Open Sans', sans-serif;
  font-size: 2em;
  line-height: 1.5;
  color: white;
  -webkit-transform:rotateY(0deg);
}

body > p { width: 50%; margin: 0 auto; text-align: center; }

h1 {
  font-family: 'Oswald', sans-serif;
  font-weight: 400;
  text-align: center;
  text-transform: uppercase;
}

h3 {
  font-family: 'Oswald';
  font-weight: 400;
  text-transform: uppercase;
  text-align: center;
}

.container {
  width: 100%;
  margin: 1.5em auto;
}

a { color: white; }

.cf:before,
.cf:after {
    content: " ";
    display: table;
}

.cf:after {
    clear: both;
}

.cf {
    *zoom: 1;
}