html {
  height: 99%
}

body {
  height: 100%;
}

div {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100%;
}

.zero {
  font-weight: bold;
  color: black;
  font-size: 100vmin;
  font-family: Fira Sans;
}