html, body { 
  height: 100%; 
  margin: 0; 
  overflow: hidden;
}
body { 
  display: flex; 
  align-items: center; 
  justify-content: center;
  background: #000; 
}
main {
  display: flex;
}
p {
  line-height: 1;
}
span {
  display: block;
  
  width: 2vmax; 
  height: 2vmax; 
  
  font-size: 2vmax; 
  color: #19FF1911;
  text-align: center;
  font-family: Helvetica, sans-serif;
}