#gallery {
  max-width: 320px;
  margin: 0 auto;
  position: relative;
  border: 2px solid #900; /* add border around the whole gallery */
  box-sizing: border-box;
}

.slideshow {
  list-style: none;
  margin: 0;
  padding: 0;
}

.slideshow li {
  position: absolute;
  top: 0; left: 0;
  width: 100%;
}

.slideshow img {
  height: auto;
  display: block;
}