.canvas {
  position: relative;
  padding-top: max(60%, 326px);
  height: 0;
  width: 100%;
}
.canvas iframe {
  position: absolute;
  border: none;
  width: 100%;
  height: 100%;
  left: 0;
  right: 0;
  top: 0;
  bottom: 0;
}