.container {
  position: fixed;
  width: 80vmin;
  height: 80vmin;
  border: 1px solid;
  top: calc(50% - 40vmin);
  left: calc(50% - 40vmin);
}
.container svg {
  width: 100%;
}

.hidden {
  display: none;
}

body {
  margin: 0;
}