html {
  font-size: 10px;
  /* We have Fira Sans as default font in real device. But it isn't default in
   * browser. That's the main reason this line is here.*/
  font-family: "Fira Sans";
}

html, body {
  width: 100%;
  height: 100%;
  overflow: auto;
  margin: 0;
  padding: 0;
  background-color: rgba(0,0,0,0.5);
}