ol5-layerswitcher/examples/layerswitcher.css

Layer switcher control for OpenLayers v3/v4/v5

html, body {
  height: 100%;
  padding: 0;
  margin: 0;
  font-family: sans-serif;
  font-size: small;
}

#map {
  width: 100%;
  height: 100%;
}