html, body {
  height: 100%;
  overflow: hidden; /* no scrollbars */
  display: flex;
  flex-direction: column;
}

h1 {
  font-family: sans-serif;
  padding: 8px;
  background: #e9f5e2;
  border-bottom: 1px solid #d5e2ce;
  text-align: center;
}

iframe {
  flex: 1; /* fill remaining height */
  border: none;
  width: 100%;
  padding-top: 30px;
}