body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  font-family: system-ui, sans-serif;
  background: #fafafa;
  color: #222;
}
.center { flex: 1; display: grid; place-content: center; text-align: center; padding: 1rem; }
@media (prefers-color-scheme: dark) {
  body { background: #111; color: #eee; }
}

footer { text-align: center; padding: 1rem; }
.support summary { display: inline-block; cursor: pointer; text-decoration: underline; }
.support iframe {
  display: block;
  width: 100%;
  max-width: 420px;
  height: 640px;
  margin: 16px auto 8px;
  border: 0;
  border-radius: 12px;
  background: #fff;
}
.support a { color: inherit; }