$card-width:       180px;
$card-outer-width: $card-width;

ul {
  white-space:    nowrap; /* allows the inline blocks to stick in a long line, not wrap like masonry. */
}
li {
  width:          $card-width;
  margin:         0;
  background:     #fc0;
  opacity:        0.1;
  @include transition( margin-left 800ms, opacity 800ms );
}

/* ONE CARD WIDE */

div {
  width:          $card-outer-width;
}
li {
  margin-left:    -100%; /* the bit that makes it all work. Each card has a default margin that makes it fold over itself, stacking them on top of each other */
}
.pointer {
  margin-left:    0;
  opacity: 1;
}
.pointer+li {
  margin-left:    0;
}

/* TWO CARDS WIDE */

@media (min-width: $card-outer-width*4) {
  div {
    width:          $card-outer-width*2;
  }
  li {
    margin-left:    -50%;
  }
  .pointer+li {
    margin-left:    0;
    opacity: 1;
  }
  .pointer+li+li {
    margin-left:    0;
  }
}

/* THREE CARDS WIDE */

@media (min-width: $card-outer-width*5) {
  div {
    width:          $card-outer-width*3;
  }
  li {
    margin-left:    -33.333%;
  }
  .pointer+li+li {
    margin-left:    0;
    opacity: 1;
  }
  .pointer+li+li+li {
    margin-left:    0;
  }
}

/* FOUR CARDS WIDE */

@media (min-width: $card-outer-width*6) {
  div {
    width:          $card-outer-width*4;
  }
  li {
    margin-left:    -25%;
  }
  .pointer+li+li+li {
    margin-left:    0;
    opacity: 1;
  }
  .pointer+li+li+li+li {
    margin-left:    0;
  }
}





/* not so interesting formatting */
* {
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}
body {
  background: #eee;
  font-family: sans-serif;
  font-size: 16px;
  color: #999;
}
div {
  position: relative;
  margin: 20px auto 0;
  padding: 0;
  background: #fff;
  box-shadow: inset 0 1px 1px 1px rgba(0,0,0,0.1);
  counter-reset: cards;
}
ul {
  margin: 0;
  padding: 0;
}
li {
  position: relative;
  display: inline-block;
  list-style: none;
  height: 250px;
  padding: 0;
  counter-increment: cards;
}
li:before {
  content: counter(cards);
  display: block;
  position: absolute;
  top: 50%;
  left: 0;
  right: 0;
  margin-top: -0.5em;
  color: rgba(255,255,255,0.7);
  font-size: 120px;
  line-height: 1;
  text-align: center;
}
.pointer {
  box-shadow: inset 0 0 0 10px #fa0;
}
.pointer:after {
  content: '.pointer';
  display: block;
  position: absolute;
  top: 12px;
  left: 12px;
  color: #f90;
}
.button {
  position: absolute;
  left: -0.25em;
  top: 50%;
  width: 2em;
  height: 2em;
  margin-top: -1em;
  padding: 0.5em;
  color: #fff;
  background: #999;
  border-radius: 50%;
  line-height: 1;
  text-align: center;
  font-family: impact;
  cursor: pointer;
}
.button-forward {
  left: auto;
  right: -0.25em;
}
.description {
  padding: 10px 20px;
}