ohif-viewer/OHIFViewer-react/src/App.css

html,
body,
#root {
  background-color: black;
  height: 100%;
  width: 100%;
  margin: 0;
}

body {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-family: Roboto,OpenSans,HelveticaNeue-Light,Helvetica Neue Light,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif;
}