:root {
  /* Base font size */
  font-size: 10px;   
  
  /* Set neon color */
  --neon-text-color: #f40;
  --neon-border-color: #08f;
}

body {
  font-family: 'Exo 2', sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;  
  background: #000;
  min-height: 100vh;
}

h1 {
  font-size: 8rem;
  font-weight: 200;
  font-style: italic;
  color: #fff;
  padding: 4rem 6rem 5.5rem;
  border: 0.4rem solid #fff;
  border-radius: 2rem;
  text-transform: uppercase;
  animation: flicker 1.5s infinite alternate;     
}

h1::-moz-selection {
  background-color: var(--neon-border-color);
  color: var(--neon-text-color);
}

h1::selection {
  background-color: var(--neon-border-color);
  color: var(--neon-text-color);
}

/* Animate neon flicker */
@keyframes flicker {
    
    0%, 19%, 21%, 23%, 25%, 54%, 56%, 100% {
      
        text-shadow:
            -0.2rem -0.2rem 1rem #fff,
            0.2rem 0.2rem 1rem #fff,
            0 0 2rem var(--neon-text-color),
            0 0 4rem var(--neon-text-color),
            0 0 6rem var(--neon-text-color),
            0 0 8rem var(--neon-text-color),
            0 0 10rem var(--neon-text-color);
        
        box-shadow:
            0 0 .5rem #fff,
            inset 0 0 .5rem #fff,
            0 0 2rem var(--neon-border-color),
            inset 0 0 2rem var(--neon-border-color),
            0 0 4rem var(--neon-border-color),
            inset 0 0 4rem var(--neon-border-color);        
    }
    
    20%, 24%, 55% {        
        text-shadow: none;
        box-shadow: none;
    }    
}