:root {
  font-family: system-ui, sans-serif;
}

main {
  max-width: 600px;
  margin: 0 auto;
}

footer, main header h1 {
  text-align: center;
}

iframe {
  border: 0;
  width: 100%;
}

iframe.short {
  height: 3rem;
}

iframe.full {
  height: 50%;
  min-height: 200px;
}

footer, i {
  color: gray;
}

footer, .small {
  font-size: smaller;
}

summary {
  cursor: pointer;
}

.inline {
  display: inline;
}

.no-list {
  list-style-type: none;
}

.top-gap {
  margin-top: 1em;
}

.invisible {
  display: none;
}

form.message button {
  vertical-align: top;
}