<div id="hoge">
  <h1>foo bar</h1>
</div>

body {
  magin: 0;
  padding: 0;
}
#hoge {
  width: 100vw;
  height: 100vh;
}
h1 {
  color: white;
  text-align: center;
  font-size: 10rem;
}

VANTA.BIRDS({
  el: "#hoge",
  mouseControls: true,
  touchControls: true,
  gyroControls: false,
  minHeight: 200.0,
  minWidth: 200.0,
  scale: 1.0,
  scaleMobile: 1.0
});