body {
  background-color:#222;
}

main { margin: 150px auto; }

#mySlideshow {
  margin: 50px auto 0;
  max-width: 600px;
  height: 450px;
  position: relative;
  overflow: hidden;
}
img {
  transform: translate(600px);
  position: absolute;
  width: 100%;
}
.showcase-img {
  transform: translate(0);
  transition: .6s;
}
.showcase-left {
  transform: translate(-600px);
  transition: .6s;
}