:host {
  display: block; --z-index: 10
}
.container {
  width: 100%; height: 100%; position: relative; z-index: var(--z-index); overflow: hidden
}
.container div.bg {
  width: 100%; background: none center center no-repeat; background-size: cover; position: absolute; position: absolute; top: -100%; left: 0px; z-index: 10; transition: top .1s ease
}
.container div.content {
  width: 100%; position: relative; z-index: 20
}