* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; font-family: Arial, Helvetica, sans-serif; }
.source-page, .source-page body { width: 100%; height: 100%; overflow: hidden; background: transparent; }
.source-page body { display: flex; }
.viewport { width: 100%; height: 100%; display: flex; align-items: center; justify-content: center; background: transparent; }
#stage { width: min(100vw, calc(100vh * 9 / 16)); height: min(100vh, calc(100vw * 16 / 9)); background: transparent; }
.sr-only { position: absolute; left: -9999px; width: 1px; height: 1px; overflow: hidden; }