#particles {
  background-size: cover;
  background-repeat: no-repeat;
  width: 100%;
  height: 100%;
  overflow: hidden;
}

@media only screen and (max-width: 1000px) {
  h1 {
    font-size: 70px;
  }
}

@media only screen and (max-width: 800px) {
  h1 {
    font-size: 48px;
  }
  h1::after {
    height: 8px;
  }
}

@media only screen and (max-width: 568px) {
  #intro {
    padding: 0 10px;
  }
  h1 {
    font-size: 30px;
  }
  h1::after {
    height: 6px;
  }
  p {
    font-size: 18px;
  }
  .btn {
    font-size: 16px;
  }
}

@media only screen and (max-width: 320px) {
  h1 {
    font-size: 28px;
  }
  h1::after {
    height: 4px;
  }
}