index.css

html {
  height: 100%;
}
body {
  height: calc(100% - 16px);
}
.help {
  position: absolute;
  top: 5em;
  right: 5em;
  z-index: 1;
  padding: 1em;
  background-color: white;
}
.status {
  position: absolute;
  top: 2px;
  right: 2px;
  z-index: 1;
  margin: 0;
  padding: 0.1em;
  background-color: white;
  animation: fadeOut 2s;
  animation-fill-mode: forwards;
}
.status > * {
  font-size: 12pt;
  margin: 0;
}
.viewer {
  width: 100%;
  height: 100%;
}
.viewer > img {
  position: relative;
}
.viewer > .caption {
  bottom: 8px;
  font-size: 1em;
  position: absolute;
  text-align: center;
  visibility: hidden;
  width: calc(100% - 16px);
}
.viewer > .spinner {
  animation: rotate 2s linear infinite;
  position: absolute;
  top: 45%;
  left: 45%;
  margin: -5% 0 0 -5%;
  width: 20%;
  height: 20%;
}
.viewer > .spinner circle {
  fill: none;
  stroke: rgb(164, 153, 247);
  stroke-linecap: round;
  stroke-width: 1px;
  animation: dash 1.5s ease-in-out infinite;
}

@keyframes rotate {
  100% {
    transform: rotate(360deg);
  }
}

@keyframes dash {
  0% {
    stroke-dasharray: 1, 150;
    stroke-dashoffset: 0;
  }
  50% {
    stroke-dasharray: 90, 150;
    stroke-dashoffset: -35;
  }
  100% {
    stroke-dasharray: 90, 150;
    stroke-dashoffset: -124;
  }
}

@keyframes fadeOut {
  0% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}