body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  background: linear-gradient(45deg, #1e3c72, #2a5298);
  background-size: 400% 400%;
  animation: gradientShift 6s infinite;
  font-family: Arial, sans-serif;
  overflow: hidden;
}

#hello-world {
  font-size: 10vw;
  font-weight: bold;
  text-transform: uppercase;
  color: white;
  text-shadow: 0 0 10px #fff, 0 0 20px #ff9, 0 0 30px #f0f, 0 0 40px #f0f, 0 0 50px #ff9, 0 0 60px #fff;
  opacity: 0;
  animation: fadeInOut 6s infinite, textGlow 2s infinite alternate;
}

@keyframes fadeInOut {
  0%, 100% {
    opacity: 0;
    transform: translateY(20px) scale(0.8);
  }
  50% {
    opacity: 1;
    transform: translateY(0) scale(1);
  }
}

@keyframes gradientShift {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

@keyframes textGlow {
  0% {
    text-shadow: 0 0 10px #fff, 0 0 20px #ff9, 0 0 30px #f0f, 0 0 40px #f0f, 0 0 50px #ff9, 0 0 60px #fff;
  }
  100% {
    text-shadow: 0 0 20px #ff9, 0 0 30px #f0f, 0 0 50px #ff9, 0 0 60px #f0f, 0 0 70px #fff;
  }
}