.stl-viewer {
  width: 100%;
  padding-top: 100%;
  position: relative;
  text-align: center;
  vertical-align: middle;

  canvas {
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
  }
}

.svs-custom { padding-top: 0% !important; margin: 0 auto; }
.svs-4-3 { padding-top: 100% !important; }
.svs-16-9 { padding-top: 100% !important; }

@media (min-width: 600px) {
  .stl-viewer { padding-top: 56.25%; }
  .svs-4-3 { padding-top: 75% !important; }
  .svs-16-9 { padding-top: 56.25% !important; }
}