style.css

html, body {
  width: 100vw;
  height: 100vh;
  margin: 0;
  overflow: hidden;
}

header h3 {
  padding: 10px 5px;
  margin: 0;
  font-family: Arial, sans-serif;
}

section {
  width: 100%;
  height: calc(100% - 40px);
}

#map1, #map2 {
  width: 49.5%;
  height: 100%;
}

#map1 { float: left; }
#map2 { float: right; }

.basemaps-wrapper {
  position: absolute;
  top: 10px;
  left: 10px;
  z-index: 1000;
}

#permalink {
  position: absolute;
  bottom: 0;
  left: 0;
  z-index: 1000;
  background: white;
  opacity: 0.8;
  font-family: Helvetica;
  font-size: 11px;
  padding: 2px;
  text-decoration: none;
  color: rgb(0, 120, 168);
  cursor: pointer;
}

#permalink:hover {
    text-decoration: underline;
}